Re: Implicit conversion to boolean in if and while statements
On Mon, Jul 16, 2012 at 2:53 PM, Ranting Rick rantingrickjohn...@gmail.com wrote: if obj is in essence doing if bool(obj) behind the scenes. My question is: Why hide such valuable information from the reader? It's obvious that if bool(obj) will return a boolean; whereas if obj is ambiguous. Proves nothing. At least when there are less names used, there's less possibility of monkey-patching. def bool(n): ... return 5 ... if bool([]): ... print(Yay?) ... Yay? ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Mon, Jul 16, 2012 at 3:03 PM, Ranting Rick rantingrickjohn...@gmail.com wrote: But if you are going to argue that if obj is *explicit enough*, then apply your argument consistently to String+1.75 also. Why must we be explicit about string conversion BUT not boolean conversion? Can you reduce this to the absurd? Or will you just choose to ignore this valid point? Personally, I'm quite okay with automatic upcasts to string. But if you want to be explicit, particularly with floats, the solution often is not to use str(), but a proper number-formatting routine. You want String%f%1.75 for full power. But when you're just letting the language do the translation, it's much of a muchness whether you put an explicit toString() call in. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On 16/07/2012 04:05, Chris Angelico wrote: On Mon, Jul 16, 2012 at 12:58 PM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: And that, the reason given in the sentence above, is the reason that we, collectively all programmers, should prefer to be explicit, not merely conveying meaning by implication about everything we, collectively all programmers, write, including typing, use of speech-recognition software, or any future technological process by which text or program code or both is transcribed from the idea of the human person to a permanent form recorded where other people, or non-human sentient beings, can read or otherwise gain access to it for the purpose of understanding the content of the test or program code or both. I'd rather be booled in oil. ChrisA *ducks for cover* What a silly bunt[1] :) *also ducks for cover* [1] from a Monty Python sketch for those who don't know about a guy who pronounces c's as b's, hence Kings Bollege Bambridge -- Cheers. Mark Lawrence. -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Jul 16, 2:53 pm, Ranting Rick rantingrickjohn...@gmail.com wrote: if obj is in essence doing if bool(obj) behind the scenes. My question is: Why hide such valuable information from the reader? If @decorator is in essence doing function = decorator(function) behind the scenes, why hide that? If classes are just syntactic sugar for dicts of functions, why hide that? It's obvious that if bool(obj) will return a boolean; whereas if obj is ambiguous. It's only ambiguous if you're the sort of idiot who believes every language should conform to their a priori expectations. The behaviour is _documented and standard_, so it's in no way ambiguous unless someone has actively failed to do _their_ part and _educate themselves_: http://docs.python.org/library/stdtypes.html#truth-value-testing If the multitudes of misunderstandings from if obj on this list have not convinced you yet By that argument, _every_ Python feature that is misunderstood should be modified to meet the expectations of those who have refused to understand the language. In which case, why even bother having different languages with different ways of doing...oh wait, I'm talking to the monoculture king. Forget that line of reasoning. Also: citation or STFU. Provide links to 3 threads from the last month that have revolved around misunderstanding of truth values. As far as I know, the only use of having a polymorphic boolean conversion is reducing the amount of typing we do. The same could be said about *every* polymorphic function. For which bool IS! Yes. That was Steven's point, which you missed in all of your usual mouth frothing. -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Jul 16, 3:03 pm, Ranting Rick rantingrickjohn...@gmail.com wrote: But if you are going to argue that if obj is *explicit enough*, then apply your argument consistently to String+1.75 also. Why must we be explicit about string conversion BUT not boolean conversion? What _other_ than booleans can you expect a condition to reduce down to? Seriously. What might you possibly expect 'obj' in 'if obj' to be? Tuesday? The colour mauve? That sinking feeling that you're entering into a debate that's far above your ability to understand it? Now: as an expression String+1.75 can be _anywhere_, so _what_ you want will very much be contextual. Do you want String1.75? Do you want float(String) + 1.75? Do you want it to error? So yes, here you very much need to be explicit. Can you reduce this to the absurd? You've already taken care of that. -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Sun, 15 Jul 2012 22:03:52 -0700, Ranting Rick wrote: But if you are going to argue that if obj is *explicit enough*, then apply your argument consistently to String+1.75 also. Why must we be explicit about string conversion BUT not boolean conversion? The problem with String + 1.75 is not lack of explicitness, but ambiguity. The + is operator is plenty explicit, but it is ambiguous when the operands have different types. Should it...? - truncate String at the first non-digit (hence ) and then coerce it to 0.0, and hence return the float 1.75? - coerce String to a float NaN on the basis that String is not a number, and hence return NaN? - coerce 1.75 to a string, and hence return String1.75? The first behaviour is rather dubious, but a good case could be made for the second or third. Python takes a fourth approach, and refuses to allow such mixed type operations. If + always meant numeric addition, and was used for string concatenation, then we could have unambiguous expressions using mixed types: 1 + 1.75 # int + float always coerces to float 1 + 2 # int + str always coerces to int 1 2 # int str always coerces to str but since is used for integer bitwise-and, and + is used for both concatenation and addition, we can't, and so Python raises an exception. For arithmetic, there is an unambiguous hierarchy of types, the numeric tower, which tells us which types coerce to what, e.g.: int - float - complex But there is no such hierarchy when it comes to (say) mixed strings and lists, etc., and hence Python raises an exception rather than guessing which type you wanted as the result. This is completely irrelevant when it comes to bools -- we don't have to coerce a value into another type, we just need to know if it is something or nothing. The object itself is best able to make that decision, hence delegating it to a protocol and method: - If the object is a container, and it has a length of 0, it is empty and hence nothing (falsey); if it has a non-zero length, it is non-empty and hence something (truthy). - Otherwise ask the container whether it is something or nothing by calling __nonzero__ (the original name) or __bool__. Python makes a rather big blunder, at least from the perspective of consistency. Bools are ints: py issubclass(bool, int) True py isinstance(True, int) True py isinstance(False, int) True but there are things that can be converted into bools that can't be converted into ints, even though bools *are* ints! Contradiction. py x = [None, 42, ''] py bool(x) True py int(x) Traceback (most recent call last): File stdin, line 1, in module TypeError: int() argument must be a string or a number, not 'list' Since x can be converted into True, and True == 1, you should be able to convert x into 1. But that's crazy, since x = [None, 42, '']. *shrug* I don't call this a gotcha, but it is one of the more ugly consequences of Python's bool implementation. Can you reduce this to the absurd? Or will you just choose to ignore this valid point? Mu. (Neither true nor false.) -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Sun, 15 Jul 2012 19:41:34 -0700, Ranting Rick wrote:
Short circuitry is a powerful tool! But why the heck would your
sequences ever be None? Are you using None as a default? And if so, why
not use an empty sequence instead ([], {}, )?
Mostly for explicitness. I want to be able to say that there is
*explicitly* no seq, not merely that it happens to be a list which right
now is empty but later might not be. Using None for missing values is
idiomatic Python.
You should approve, if only for the sake of consistency: None is meant to
be used as no such value, and that's exactly how I am using it, even at
the cost of my convenience when writing the code.
--
Steven
--
http://mail.python.org/mailman/listinfo/python-list
Re: Diagramming code
Am 16.07.2012 03:57, schrieb hamilton: OK then, let me ask, how do you guys learn/understand large projects ? 1. Use the program. This gives you an idea what features are there and a bit how it could be structured. 2. Build the program, to see what is done to get the program running. This should give you an idea what pieces there are and where they are [from]. 3. Read design documentation (which is too often outdated) which should give you an idea what the intention of the project's structure is. 4. Read the code documentation (which is hopefully more up to date). This should give you an idea about responsibilities within the code. 5. Read the code itself. This can also be done while single-stepping through it with a debugger, just to see it run. Of course there are also secondary resources like developers' and users' mailinglists, websites, bugtrackers that provide information and help. Sometimes, drawing a few diagrams from steps 3 and 4 to document relationships between things is helpful. IMHO having a text describing the relationships in prose is superior to that though. In particular a diagram can't describe the rationale for something, you need prose for that. HTH YMMV Uli -- http://mail.python.org/mailman/listinfo/python-list
Re: Diagramming code
On Mon, Jul 16, 2012 at 3:58 AM, Ulrich Eckhardt ulrich.eckha...@dominolaser.com wrote: Am 16.07.2012 03:57, schrieb hamilton: OK then, let me ask, how do you guys learn/understand large projects ? 1. Use the program. This gives you an idea what features are there and a bit how it could be structured. 2. Build the program, to see what is done to get the program running. This should give you an idea what pieces there are and where they are [from]. 3. Read design documentation (which is too often outdated) which should give you an idea what the intention of the project's structure is. 4. Read the code documentation (which is hopefully more up to date). This should give you an idea about responsibilities within the code. 5. Read the code itself. This can also be done while single-stepping through it with a debugger, just to see it run. Of course there are also secondary resources like developers' and users' mailinglists, websites, bugtrackers that provide information and help. Sometimes, drawing a few diagrams from steps 3 and 4 to document relationships between things is helpful. IMHO having a text describing the relationships in prose is superior to that though. In particular a diagram can't describe the rationale for something, you need prose for that. HTH YMMV Uli -- http://mail.python.org/mailman/listinfo/python-list Do you know about pydoc? Its a great way to get a handle on your modules. It doesn't make diagrams, but a synopsis of what is in the module. It makes use of docstrings, for the module and each class and function in the module. -- Joel Goldstick -- http://mail.python.org/mailman/listinfo/python-list
Re: Tkinter.event.widget: handler gets name instead of widget.
On Sat, 2012-07-14 at 20:10 -0700, rantingrickjohn...@gmail.com wrote: On Thursday, July 12, 2012 1:53:54 PM UTC-5, Frederic Rentsch wrote: The hit list is a table of investment titles (stock, funds, bonds) that displays upon entry of a search pattern into a respective template. The table displays the matching records: name, symbol, ISIN, CUSIP, Sec. Any line can be click-selected. So they are to look like buttons. Hmm. If they appear like a button widget anyway, then why not just use a button widget? Why indeed? Why does one do simple things in a complicated way? Stations on the sinuous path the explorer takes surveying unknown territory, I guess. Your example below is just what I need. Thanks! Representing the mentioned names and id codes in Label widgets was the simplest way I could come up with to align them in columns, admittedly without the benefit of much experience. But it does look good. the layout is fine. But is it really the simplest? :) ## START CODE ## import Tkinter as tk from Tkconstants import * colWidths = (5,10,30,5) N_COLS = len(colWidths) N_ROWS = 6 root = tk.Tk() for r in range(N_ROWS): # Create some imaginary text to display in each column. # Also try using string methods center and rjust to # see alternative justification of text. lst = [str(r).ljust(colWidths[r]) for r in range(N_COLS)] b=tk.Button(root, text=''.join(lst)) b.pack(padx=5, pady=5) root.mainloop() ## END CODE ## You could easily expand that into something reusable. Now. If you need to place fancy borders around the texts, or use multiple fonts, or use images, or blah blah blah... then you may want to use the canvas items provided by the Tkinter.Canvas widget INSTEAD of buttons. With the canvas, you can create a simple rectangle (canvas.create_rectangle) that represents a button's outside dimension and give it a button styled border. Then you can bind click events to mimic the button press action. Then you can place canvas_text items on top of that fake button and configure them to be invisible to click events. These text items will not interfer like the Tkinter.Label widgets are currently doing. However, i would suggest the Tkinter.Button solution is the easiest by far. I find the Tkinter system quite challenging. Doing a layout isn't so much a matter of dimensioning and placing things as a struggle to trick a number of automatic dimensioning and placing mechanisms into obliging--mechanisms that are rather numerous and hard to remember. I don't think i agree with that assessment. Sticky, justify, side, anchor, width, height, pad, ipad . . . a plethora of similar formatting concepts with applicability, precedence and effect rules that are certainly easy to work with once one knows them inside out. Until such time it's much trial-and-error, and reading of course, which also frequently involves guessing what is meant and cross-checking by experiment. For instance, I had to find a way to control the size of frames. The geometry mangers deflate everything bottom to top and utterly ignore width and height specifications unless the widget is empty. The solution I found was spanners, frames slimmed down to zero whose length acts as a foot in the door of their parent, as it were. I suspect there are better ways. ## START TANGENTIAL MEANDERINGS ## I find the geometry management of Tkinter to be quite powerful whilst being simultaneously simplistic. You only have three main types of management: Grid, Place, and Pack. Each of which has a very specific usage. One caveat to know is that you can NEVER mix Grid and Pack in the same container widget! I find myself using grid and pack the most, with grid being at the top of the list. Now, i will agree that grid can be confusing at first until you understand how to rowconfigure and columnconfigue the containing widget (be it a frame or a toplevel). There is also the sticky attribute to consider. ## END TANGENTIAL MEANDERINGS ## Thanks for the reminder. But all in all, i would say the most difficult part of the Tkinter geometry management API is coming to grips as to which of the three geometry managers is the best choice for the particular problem at hand -- and you will find yourself using more than one manager in a single GUI app! But i don't see you solving this problem by stacking one widget on another. I believe it's time to seek out a new solution. I agree. Your idea of using pre-formatted text in buttons is definitely the way to go. EASY: Using rows of Tkinter.Button coupled with a per-formatted text string. ADVANCED: Creating pseudo buttons on a canvas and stacking text objects (or whatever you like) on them. I'll keep that in mind. Finally I can report that I found the error I started this thread with. (Attribute 'widget' of an event was type str) I have a Frame Data as a container of all sorts
Re: code review
Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Fri, 13 Jul 2012 12:30:47 +, Albert van der Horst wrote: The worst of is, of course, = for assignment instead of := . This is a convention that Python follows, to my dismay. *shrug* The worst is to use = for both equality and assignment, like some BASICs. At least Python does not allow assignment as an expression, so you can't make the typical C error of: if x = y: do_something() # oops meant x == y Technically of course Python doesn't have assignment, it just binds names. Albert raised the subject of Algol 68 which if I remember correctly used := for assignment and = to bind names (although unlike Python you couldn't then re-bind the name to another object in the same scope). -- Duncan Booth http://kupuguy.blogspot.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Initial nose experience
On 07/15/2012 08:58 PM, Roy Smith wrote: What motivated you to migrate from unittest to nose? Mostly I was just looking for a better way to run our existing tests. We've got a bunch of tests written in standard unittest, but no good way to start at the top of the tree and run them all with a single command. Currently, $ python -m unittest does nothing useful (afaik). Would it break anything to look in . , ./test, ./tests for any files matching test_* , and execute those? - Philipp signature.asc Description: OpenPGP digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Initial nose experience
In article mailman.2149.1342375358.4697.python-l...@python.org, pyt...@bdurham.com wrote: After years of using unittest, what would you say are the pros and cons of nose? BTW, although I'm currently using nose just as a unittest aggregator, I can see some nice advantages to native nose functionality. The most obvious is that tests can be plain-old static functions at the top level of a module. In unittest, you have to subclass TestCase, then write methods for that (showing its JUnit/SUnit roots). In 99% of the tests I write, I don't do anything special in my TestCase subclasses, so that's all just boilerplate busywork. I like the idea that I can skip that all now. -- http://mail.python.org/mailman/listinfo/python-list
Re: code review
Duncan Booth duncan.booth@invalid.invalid writes: Technically of course Python doesn't have assignment, it just binds names. Names, or other references. I'd argue that Python has assignment, and assignment in Python is identical with binding references to objects. But then, the Python documentation refers to “variables” as though they exist in Python, which I'd argue they don't. It's all very confusing :-) -- \ “Religious faith is the one species of human ignorance that | `\ will not admit of even the *possibility* of correction.” —Sam | _o__) Harris, _The End of Faith_, 2004 | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: Initial nose experience
Philipp Hagemeister wrote: Currently, $ python -m unittest does nothing useful (afaik). Would it break anything to look in . , ./test, ./tests for any files matching test_* , and execute those? http://docs.python.org/library/unittest#test-discovery -- http://mail.python.org/mailman/listinfo/python-list
unittest: Improve discoverability of discover (Was: Initial nose experience)
On 07/16/2012 01:47 PM, Peter Otten wrote: http://docs.python.org/library/unittest#test-discovery That's precisely it. Can we improve the discoverability of the discover option, for example by making it the default action, or including a message use discover to find test files automatically if there are no arguments? - Philipp signature.asc Description: OpenPGP digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Initial nose experience
Roy Smith r...@panix.com writes: In article mailman.2149.1342375358.4697.python-l...@python.org, pyt...@bdurham.com wrote: After years of using unittest, what would you say are the pros and cons of nose? BTW, although I'm currently using nose just as a unittest aggregator Be aware that Python 2.7 and higher has unit test discovery in the standard library: $ python -m unittest discover will look through all packages within the current directory and collect unit tests it finds, then run them and report URL:http://docs.python.org/library/unittest.html#test-discovery. You can get the same in earlier versions of Python with ‘unittest2’ URL:http://pypi.python.org/pypi/unittest2. -- \ “I prayed for twenty years but received no answer until I | `\ prayed with my legs.” —Frederick Douglass, escaped slave | _o__) | Ben Finney -- http://mail.python.org/mailman/listinfo/python-list
Re: unittest: Improve discoverability of discover (Was: Initial nose experience)
On 07/16/2012 02:37 PM, Philipp Hagemeister wrote: Can we improve the discoverability of the discover option, for example by making it the default action, or including a message use discover to find test files automatically if there are no arguments? Oops, already implemented as of Python 3.2. Sorry, should've checked before. - Philipp signature.asc Description: OpenPGP digital signature -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On 15.07.12 19:50, Rick Johnson wrote: We must NEVER present if in such confusing manner as ExampleA. ## EXAMPLE C ## py if bool(money) == True: ... do_something() -- http://mail.python.org/mailman/listinfo/python-list
assertraises behaviour
I found that the behaviour of assertRaises used as a context manager a bit surprising. This small example doesn't fail, but the OSError exception is cathed even if not declared.. Is this the expected behaviour (from the doc I would say it's not). (Running on arch-linux 64 bits and Python 2.7.3, but it doesn the same with Python 3.2.3) import unittest class TestWithRaises(unittest.TestCase): def test_ass(self): with self.assertRaises(AssertionError): assert False, should happen raise OSError(should give error) if __name__ == '__main__': unittest.main() -- http://mail.python.org/mailman/listinfo/python-list
Re: assertraises behaviour
Am 16.07.2012 15:38, schrieb andrea crotti: This small example doesn't fail, but the OSError exception is cathed even if not declared.. Is this the expected behaviour (from the doc I would say it's not). (Running on arch-linux 64 bits and Python 2.7.3, but it doesn the same with Python 3.2.3) import unittest class TestWithRaises(unittest.TestCase): def test_ass(self): with self.assertRaises(AssertionError): assert False, should happen raise OSError(should give error) The OSError isn't catched as the code never reaches the line with raise OSError. In other words raise OSError is never executed as the exception raised by assert False stops the context manager. You should avoid testing more than one line of code in a with self.assertRaises() block. Christian -- http://mail.python.org/mailman/listinfo/python-list
Re: Python and Qt4 Designer
On 07/15/2012 01:58 AM, Vincent Vande Vyvre wrote: Rusi is not the op, and his question is about these lines app = None if ( not app ): Yeah that's a no-op. The original author of that code is clearly confused there. not this one app = QtGui.QApplication([]) which should be written like this app = QtGui.QApplication(sys.argv) Yeah. The QApplication not only is the main engine, but it also parses the command-line for certain flags that influence Qt's behavior, similar to gtk's main function that also parses command-line flags (specific to gtk's operation). -- http://mail.python.org/mailman/listinfo/python-list
Re: Discussion on some Code Issues
On Sunday, July 8, 2012 10:47:00 PM UTC+5:30, Chris Angelico wrote: On Mon, Jul 9, 2012 at 3:05 AM, lt;subhabangal...@gmail.comgt; wrote: gt; On Sunday, July 8, 2012 1:33:25 PM UTC+5:30, Chris Angelico wrote: gt;gt; On Sun, Jul 8, 2012 at 3:42 PM, lt;subhabangal...@gmail.comgt; wrote: gt;gt; gt; file_open=open(quot;/python32/doc1.txtquot;,quot;rquot;) gt;gt; Also, as has already been mentioned: keeping your data files in the gt;gt; Python binaries directory isn#39;t usually a good idea. More common to gt;gt; keep them in the same directory as your script, which would mean that gt;gt; you don#39;t need a path on it at all. gt; No file path! Amazing. I do not know I like to know one small example please. open(quot;doc1.txtquot;,quot;rquot;) Python will look for a file called doc1.txt in the directory you run the script from (which is often going to be the same directory as your .py program). gt; Btw, some earlier post said, line.split() to convert line into bag of words can be done with power(), but I did not find it, if any one can help. I do close files do not worry. New style I#39;d try. I don#39;t know what power() function you#39;re talking about, and can#39;t find it in the previous posts; the nearest I can find is a post from Ranting Rick which says a lot of guff that you can ignore. (Rick is a professional troll. Occasionally he says something useful and courteous; more often it#39;s one or the other, or neither.) As to the closing of files: There are a few narrow issues that make it worth using the #39;with#39; statement, such as exceptions; mostly, it#39;s just a good habit to get into. If you ignore it, your file will *usually* be closed fairly soon after you stop referencing it, but there#39;s no guarantee. (Someone else will doubtless correct me if I#39;m wrong, but I#39;m pretty sure Python guarantees to properly flush and close on exit, but not necessarily before.) ChrisA Dear Group, The problem is more or less solved. Thank you for giving varied ways of thinking on the problem. Everytime I visit the group I learn so many things. Thank you all for taking your kind time to try to absolve the issue. Regards, Subhabrata Banerjee. -- http://mail.python.org/mailman/listinfo/python-list
Re: assertraises behaviour
2012/7/16 Christian Heimes li...@cheimes.de: The OSError isn't catched as the code never reaches the line with raise OSError. In other words raise OSError is never executed as the exception raised by assert False stops the context manager. You should avoid testing more than one line of code in a with self.assertRaises() block. Christian -- http://mail.python.org/mailman/listinfo/python-list Ok now it's more clear, and normally I only test one thing in the block. But I find this quite counter-intuitive, because in the block I want to be able to run something that raises the exception I catch (and which I'm aware of), but if another exception is raised it *should* show it and fail in my opinion.. -- http://mail.python.org/mailman/listinfo/python-list
Re: assertraises behaviour
andrea crotti wrote: 2012/7/16 Christian Heimes li...@cheimes.de: The OSError isn't catched as the code never reaches the line with raise OSError. In other words raise OSError is never executed as the exception raised by assert False stops the context manager. You should avoid testing more than one line of code in a with self.assertRaises() block. Christian -- http://mail.python.org/mailman/listinfo/python-list Ok now it's more clear, and normally I only test one thing in the block. But I find this quite counter-intuitive, because in the block I want to be able to run something that raises the exception I catch (and which I'm aware of), but if another exception is raised it *should* show it and fail in my opinion.. That doesn't sound like it's clearer. Perhaps it helps if you translate your code into a standard try...except: class A(Exception): pass ... class B(Exception): pass ... try: ... raise A ... raise B ... except A as e: ... print caught %r % e ... caught A() The try block is left at the raise A' statement -- Python doesn't have an equivalent of Basic's resume next. Therefore B (or OSError) is never raised. PS: Strictly speaking your assert False is equivalent to if __debug__ and False: raise AssertionError Therefore you *can* trigger the OSError by invoking the interpreter with the -O option: $ python -c 'assert False; raise OSError' Traceback (most recent call last): File string, line 1, in module AssertionError $ python -O -c 'assert False; raise OSError' Traceback (most recent call last): File string, line 1, in module OSError -- http://mail.python.org/mailman/listinfo/python-list
Style question: metaclass self vs cls?
Here's a style question for you: in a metaclass, what should I call the instance parameter of methods, cls or self? class ExampleMeta(type): def method(self, *args): ... I'm not quite sure if that feels right. On the one hand, self is the ExampleMeta instance alright... but on the other, self is actually a class, so I feel I want to call it cls rather than self, which makes it more obvious that you're looking at a metaclass. On the third-hand, it may be confusing that the argument is called cls but not decorated with classdecorator. I'm very slightly leaning towards writing metaclasses like this: class ExampleMeta(type): def __new__(meta, *args): ... def method(cls, *args): ... class Example(metaclass=ExampleMeta): def another_method(self): ... What do others do? -- Steven -- http://mail.python.org/mailman/listinfo/python-list
PyQt QCalendarWidget events question
I am trying to use the PyQt4 calendar widget to perform some different actions on specific dates. There are three events available:- selectionChanged() activated(QDate) clicked(QDate) On trying all these out it would appear that the event handlers get called as follows:- The clicked(QDate) event gets called if you click on an already selected date. The selectionChanged() and then the clicked(QDate) events are called when you click on a new date. The selectionChanged(), then the clicked(QDate) and then the activated(QDate) events are called if you double-click on a new date. The clicked(QDate) and then the activated(QDate) events are called if you double-click on an already selected date. How can I get a single-click on a date to get 'Action1' and double-click on a date to get 'Action2'? -- Chris Green -- http://mail.python.org/mailman/listinfo/python-list
Re: PyQt QCalendarWidget events question
tinn...@isbd.co.uk wrote: I am trying to use the PyQt4 calendar widget to perform some different actions on specific dates. There are three events available:- selectionChanged() activated(QDate) clicked(QDate) On trying all these out it would appear that the event handlers get called as follows:- The clicked(QDate) event gets called if you click on an already selected date. The selectionChanged() and then the clicked(QDate) events are called when you click on a new date. The selectionChanged(), then the clicked(QDate) and then the activated(QDate) events are called if you double-click on a new date. The clicked(QDate) and then the activated(QDate) events are called if you double-click on an already selected date. How can I get a single-click on a date to get 'Action1' and double-click on a date to get 'Action2'? I'm sorry, this got sent a bit before I'd completed it. The trouble is that I want to run Action1 if I single-click on a date whether or not it's a changed date and I want to run Action2 if I double-click on a date whether or not it's a changed date. However I don't see how I can do this because of the order in which the event handlers are called. Is there any way to manipulate this so I can get the result I want? At the moment the only way I can see to do it is to wait a while after a click and then look at what actions occurred but this seems a real bodge. -- Chris Green -- http://mail.python.org/mailman/listinfo/python-list
Re: assertraises behaviour
Good thanks, but there is something that implements this behaviour.. For example nose runs all the tests, and if there are failures it goes on and shows the failed tests only in the end, so I think it is possible to achieve somehow, is that correct? -- http://mail.python.org/mailman/listinfo/python-list
RE: Diagramming code
You leave many relevant questions unanswered. 1. Is the original developer/team available or have you been left with the code and little or no doc's? 2. How big is big in terms of the number of files/modules in the project? 3. Is there a reasonable structure to the project in terms of directories and a meaningful hierarchy 4. Does the project currently work and you just have to maintain/enhance it or was it abandoned by the original team in an unknown state and you have to save a sinking ship? 5. Are you an experienced Python programmer or a beginner. 6. Is the original code pythonic (i.e. clean and simple with brief, well organized methods) or do you have functions over 50 lines of code with multiple nested control statements and meaningless variable names? 7. Is there any documentation that defines what it should do and how it should do it. i.e. how do you know when it's working? These issues are not really Python specific, but if you've been given a broken project that has 200 poorly organized modules and little or no documentation and no access to the original team, a good first step would be to update your resume ;) OK then, let me ask, how do you guys learn/understand large projects ? hamilton -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
In article b2971c4d-0769-4d03-a7b6-c527629a8...@x39g2000yqx.googlegroups.com, Ranting Rick rantingrickjohn...@gmail.com wrote: We DON'T want Python to silently convert cost to a string. What we DO want is to force the author to use the str function thereby making the conversion explicit. We do want Python to silently convert cost to a string in the proper context. cost= 3.75 print( cost ) Same with converting objects to bools. I think if is sufficient context to convert something to a boolean. It now is a matter of good taste and what fits best in Python as a whole. Nothing to be dogmatic about. Groetjes Albert -- -- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- being exponential -- ultimately falters. albert@spearc.xs4all.nl =n http://home.hccnet.nl/a.w.m.van.der.horst -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
In article 50038364$0$29995$c3e8da3$54964...@news.astraweb.com, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Sun, 15 Jul 2012 18:21:06 -0700, Ranting Rick wrote: If HOWEVER we want to truth test an object (as in: if obj) we should be FORCED to use the bool! Why? Because explicit is better than implicit And this is why Rick always writes code like: integer_value_three = int(1) + int(2) assert (int(integer_value_three) == \ int(3) is True) is True, str(arithmetic failed) list_containing_three_values_which_are_all_integers_but_might_later_have_more_or_fewer_values_or_other_types = list([1, 2, integer_value_three]) because you can never have too much explicitness. Who wouldn't want to read code like that? Java programmers? (Couldn't resist ;-) ) -- Steven Groetjes Albert -- -- Albert van der Horst, UTRECHT,THE NETHERLANDS Economic growth -- being exponential -- ultimately falters. albert@spearc.xs4all.nl =n http://home.hccnet.nl/a.w.m.van.der.horst -- http://mail.python.org/mailman/listinfo/python-list
Re: assertraises behaviour
andrea crotti wrote: Good thanks, but there is something that implements this behaviour.. For example nose runs all the tests, and if there are failures it goes on and shows the failed tests only in the end, so I think it is possible to achieve somehow, is that correct? No, I don't see how the code you gave above can fail with an OSError. Can you give an example that produces the desired behaviour with nose? Maybe we can help you translate it to basic unittest. -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
Steven D'Aprano wrote: On Sun, 15 Jul 2012 10:19:16 -0600, Ian Kelly wrote: On Sun, Jul 15, 2012 at 4:56 AM, Steven D'Aprano wrote: (For the record, I can only think of one trap for the unwary: time objects are false at *exactly* midnight.) Ugh, that's irritating. I can't think of any scenario where I would ever want the semantics if timeval (is not midnight):. Yes, it is a genuine gotcha. Time values are numbers, and zero is falsey, so midnight is falsey even though it shouldn't be. There's no good solution here, since we have a conflict between treating time values as time values (midnight is nothing special) and as numbers (midnight == 0 which is falsey). -- import datetime -- mn = datetime.time(0) -- mn datetime.time(0, 0) -- mn == 0 False Apparently, midnight does not equal zero. Possibly because it should be truthy. ;) ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list
Re: Diagramming code
Thank you Fred. I am new to python and am reviewing code I find online. Some projects do have docs that spell out what its doing, but many projects that I have download have just the code. I have my own personal style to decypher C and C++ code. But python is still foreign to me. hamilton On 7/16/2012 11:02 AM, Sells, Fred wrote: You leave many relevant questions unanswered. 1. Is the original developer/team available or have you been left with the code and little or no doc's? 2. How big is big in terms of the number of files/modules in the project? 3. Is there a reasonable structure to the project in terms of directories and a meaningful hierarchy 4. Does the project currently work and you just have to maintain/enhance it or was it abandoned by the original team in an unknown state and you have to save a sinking ship? 5. Are you an experienced Python programmer or a beginner. 6. Is the original code pythonic (i.e. clean and simple with brief, well organized methods) or do you have functions over 50 lines of code with multiple nested control statements and meaningless variable names? 7. Is there any documentation that defines what it should do and how it should do it. i.e. how do you know when it's working? These issues are not really Python specific, but if you've been given a broken project that has 200 poorly organized modules and little or no documentation and no access to the original team, a good first step would be to update your resume ;) OK then, let me ask, how do you guys learn/understand large projects ? hamilton -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Diagramming code
Is there any software to help understand python code ? For module dependency you can try http://furius.ca/snakefood/ -- http://mail.python.org/mailman/listinfo/python-list
Re: Re: PyQt QCalendarWidget events question
On 7/16/2012 12:28 PM, tinn...@isbd.co.uk wrote: tinn...@isbd.co.uk wrote: I am trying to use the PyQt4 calendar widget to perform some different actions on specific dates. There are three events available:- selectionChanged() activated(QDate) clicked(QDate) On trying all these out it would appear that the event handlers get called as follows:- The clicked(QDate) event gets called if you click on an already selected date. The selectionChanged() and then the clicked(QDate) events are called when you click on a new date. The selectionChanged(), then the clicked(QDate) and then the activated(QDate) events are called if you double-click on a new date. The clicked(QDate) and then the activated(QDate) events are called if you double-click on an already selected date. How can I get a single-click on a date to get 'Action1' and double-click on a date to get 'Action2'? I'm sorry, this got sent a bit before I'd completed it. The trouble is that I want to run Action1 if I single-click on a date whether or not it's a changed date and I want to run Action2 if I double-click on a date whether or not it's a changed date. However I don't see how I can do this because of the order in which the event handlers are called. Is there any way to manipulate this so I can get the result I want? At the moment the only way I can see to do it is to wait a while after a click and then look at what actions occurred but this seems a real bodge. I suspect that the consensus would be don't do that -- having single-click and double click perform unrelated actions. But here's an implementation based on the advice at http://www.qtcentre.org/threads/7858-Double-Click-Capturing (use Ctrl-Break to break out of the event loop) import PyQt4.QtCore as C import PyQt4.QtGui as G class Button(G.QPushButton): def __init__(self, text): G.QPushButton.__init__(self, text) # flag to suppress second mouseReleaseEvent # in this double-click event sequence: # 1. mousePressEvent # 2. mouseReleaseEvent # 3. mouseDoubleClickEvent # 4. mouseReleaseEvent self.double_clicked = False def mouseReleaseEvent(self, evt): # executed for first mouseReleaseEvent if not self.double_clicked: self.first_click_timer = C.QTimer() self.first_click_timer.setSingleShot(True) # double-click must occur within 1/4 second of first-click release self.first_click_timer.setInterval(250) self.first_click_timer.timeout.connect(self.single_click_action) self.first_click_timer.start() # executed for second mouseReleaseEvent else: # reset the flag self.double_clicked = False def single_click_action(self): print Performing single-click action def mouseDoubleClickEvent(self, evt): # suppress the single-click action; perform double-click action instead self.first_click_timer.stop() print Performing double-click action # prepare for second mouseReleaseEvent self.double_clicked = True # main program app = G.QApplication([]) button = Button(Click or double-click me) button.show() app.exec_() HTH, John -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On 7/15/2012 9:38 PM, Steven D'Aprano wrote: I would expect None to mean doesn't exist or unknown or something like that - e.g., a value of 0 means 0 jelly beans in the jar and None means there isn't a jar. How you interpret some_variable = None depends on what some_variable represents. If some_variable represents number of jelly beans in a jar, then that should be 0 if there is no jar. What is None supposed to mean then, and what should I do when I have to make a distinction between doesn't exist and empty? Sure, if I need to count the total number of jelly beans in all my stores, the distinction is meaningless, but if I need to find out which stores sell jelly beans so I know which stores need to be restocked, the distinction is quite important. -- CPython 3.3.0b1 | Windows NT 6.1.7601.17803 -- http://mail.python.org/mailman/listinfo/python-list
Re: Diagramming code
On 07/16/2012 02:26 AM, hamilton wrote: Is there any software to help understand python code ? Thanks hamilton Sometimes to get some nice graphs I use gprof2dot (http://code.google.com/p/jrfonseca/wiki/Gprof2Dot) or doxygen (http://www.stack.nl/~dimitri/doxygen/) gprof2dot analyses the output of the profiling that you get running the code through the python profiler, doing for example: python -m cProfile -o $STATS $FNAME $@ $GPROF2DOT -f pstats $STATS | dot -T$TYPE -o $OUT doxygen is more useful for C++ but it's also able to infer a few things (without running) from a python project.. -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
Andrew Berg wrote: On 7/15/2012 9:38 PM, Steven D'Aprano wrote: I would expect None to mean doesn't exist or unknown or something like that - e.g., a value of 0 means 0 jelly beans in the jar and None means there isn't a jar. How you interpret some_variable = None depends on what some_variable represents. If some_variable represents number of jelly beans in a jar, then that should be 0 if there is no jar. What is None supposed to mean then, and what should I do when I have to make a distinction between doesn't exist and empty? Sure, if I need to count the total number of jelly beans in all my stores, the distinction is meaningless, but if I need to find out which stores sell jelly beans so I know which stores need to be restocked, the distinction is quite important. I'm not sure what Steven was trying to say there, but for me: jar with no jellybeans == 0 no jar == None ~Ethan~ -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
... Traceback (most recent quip last): Author: DeAprano, line 7, in post LogicalFallacyError: Reductio ad absurdum Deary deary me Rick. Reductio ad adsurdum is not a fallacy. It is a counter-argument to an argument or claim, by showing that the premise of the original claim leads to an absurd conclusion. You have claimed that we should always be explicit whenever we write. But you do not actually live up to your own advice, because you can't: it is absurd to try to be explicit about everything all the time. You have misunderstood the purpose of the Zen of Python: it is not to claim that everything should be explicit, but to avoid code that is hard to understand because things which need to be explicit for clarity are implied by other parts of your code. I agree. There is no pont in abolutizing explicitness anyway. It is not a yes/no question. You cannot tell that somebody is not explicit. It is not something that can be decided. But you can say that he was not explicit enough in a concrete case. There is an accepted level of explicitness. You can probably always be more expicit, or less explicit. Being more explicit is not the goal. But is a good practice to be more explicit if it helps you achieve the real goal. For example, writting a program that can be maintained easily. -- http://mail.python.org/mailman/listinfo/python-list
Re: No more Python support in NetBeans 7.0
On Wednesday, October 26, 2011 8:06:16 PM UTC-6, w...@naveed.net wrote: Sorry to comment on an old topic, but I wanted to clarify for others like me who might get the wrong idea. It looks like this is no longer true. Netbeans 7 might be supporting python after all. http://wiki.netbeans.org/Python70Roadmap This article is dated January 29th of 2011 http://netbeans.org/projects/www/lists/nbpython-dev/archive/2011-01/message/0 -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
This syntax is explicit *enough*. We don't need to be any more explicit. But if you are going to argue that if obj is *explicit enough*, then apply your argument consistently to String+1.75 also. Why must we be explicit about string conversion BUT not boolean conversion? Can you reduce this to the absurd? Or will you just choose to ignore this valid point? Not all decisions in Python are based purely on the explicit enough thing. Some things in the language cannot be explained using explicitness alone. So, when we cannot fully explain the ' why String+1.75 ' question with statements about explicitness then it doesn't mean that anybody lied or wrote something wrong. :-) -- http://mail.python.org/mailman/listinfo/python-list
Re: No more Python support in NetBeans 7.0
On Wednesday, October 26, 2011 8:06:16 PM UTC-6, w...@naveed.net wrote: Sorry to comment on an old topic, but I wanted to clarify for others like me who might get the wrong idea. It looks like this is no longer true. Netbeans 7 might be supporting python after all. http://wiki.netbeans.org/Python70Roadmap I checked the date on that document it's last update was 5 November 2009 -- http://mail.python.org/mailman/listinfo/python-list
Re: Style question: metaclass self vs cls?
On 7/16/2012 11:29 AM, Steven D'Aprano wrote: Here's a style question for you: in a metaclass, what should I call the instance parameter of methods, cls or self? class ExampleMeta(type): def method(self, *args): ... I'm not quite sure if that feels right. On the one hand, self is the ExampleMeta instance alright... but on the other, self is actually a class, so I feel I want to call it cls rather than self, which makes it more obvious that you're looking at a metaclass. I have never seriously written a metaclass, but as a reader I would prefer 'cls'. On the third-hand, it may be confusing that the argument is called cls but not decorated with classdecorator. To me, that reinforces 'looking as a metaclass'. An @classmethod in a class is a class method specific to the particular class. A method in a metaclass is a method common to all classes of the metaclass. They could be written differently, yet calling the first param 'cls' either way seems reasonable. I'm very slightly leaning towards writing metaclasses like this: class ExampleMeta(type): def __new__(meta, *args): ... def method(cls, *args): ... class Example(metaclass=ExampleMeta): def another_method(self): ... What do others do? Not too many people write real metaclasses. Python lets you chose. Have you looked at the C code of type? (Not that you are bound by it.) -- Terry Jan Reedy -- http://mail.python.org/mailman/listinfo/python-list
Re: Diagramming code
On 16/07/2012 21:41, Andrea Crotti wrote: On 07/16/2012 02:26 AM, hamilton wrote: Is there any software to help understand python code ? Thanks hamilton Sometimes to get some nice graphs I use gprof2dot (http://code.google.com/p/jrfonseca/wiki/Gprof2Dot) or doxygen (http://www.stack.nl/~dimitri/doxygen/) gprof2dot analyses the output of the profiling that you get running the code through the python profiler, doing for example: python -m cProfile -o $STATS $FNAME $@ $GPROF2DOT -f pstats $STATS | dot -T$TYPE -o $OUT doxygen is more useful for C++ but it's also able to infer a few things (without running) from a python project.. +1 for doxygen. Combined with http://code.foosel.org/doxypy , it is a fully featured solution. I use it for all my projects, python and otherwise. ~Andrew -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Mon, 16 Jul 2012 13:54:32 -0700, Ethan Furman wrote: Andrew Berg wrote: On 7/15/2012 9:38 PM, Steven D'Aprano wrote: I would expect None to mean doesn't exist or unknown or something like that - e.g., a value of 0 means 0 jelly beans in the jar and None means there isn't a jar. How you interpret some_variable = None depends on what some_variable represents. If some_variable represents number of jelly beans in a jar, then that should be 0 if there is no jar. What is None supposed to mean then, and what should I do when I have to make a distinction between doesn't exist and empty? Sure, if I need to count the total number of jelly beans in all my stores, the distinction is meaningless, but if I need to find out which stores sell jelly beans so I know which stores need to be restocked, the distinction is quite important. I'm not sure what Steven was trying to say there, but for me: jar with no jellybeans == 0 no jar == None The existence of a jar or no jar is irrelevant to the question of how many jellybeans there are. They are two different things, and therefore need two different values. There are many ways to implement this. # One way jar_exists = True # or possibly False jellybeans = 42 # or whatever the number is, possibly 0 # Another way jar = Jar(number_of_beans=jellybeans) if jar_exists else None jellybeans = jar.jellybeans if jar is not None else 0 If you have many jars, and you want to count the total number of jellybeans: total = sum(jar.jellybeans for jar in jars if jar is not None) Strictly speaking, the is not None is redundant, but it expresses the intent better than the alternative. Assuming that jar instances follow the standard Python API for containers, and is treated as falsey when it has a jellybean count of zero: total = sum(jar.jellybeans for jar in jars if jar) # relies on the fact that adding zero to a number makes # no difference, so you can safely leave zeroes out Here's a case where you *must* distinguish between empty jars and None: number_of_jars = sum(1 for jar in jars if jar is not None) and a case where you *shouldn't*: number_of_nonempty_jars = sum(1 for jar in jars if jar) Of course you can write this: number_of_nonempty_jars = sum( 1 for jar in jars if jar is not None and jar.jellybeans 1 ) but that overwhelms the code with incidental implementation details about jellybean counts, which is prone to bugs. (Did you spot it?) Even jar.isempty() would be better, but better still is to *not* invent your own container API but to use the standard Python one instead and define an appropriate __nonzero__ (Python 2) or __bool__ (Python 3) method. If I insist on making a single object do duty for both the jar and the jellybean count, then I need a null jar object, and I probably end up with something like this: Jar(number_of_beans=None) = null jar object with jar.jellybeans = 0 Jar(number_of_beans=0) = normal jar object with jar.jellybeans = 0 Jar(number_of_beans=42) = normal jar object with jar.jellybeans = 42 and then my code becomes even more complicated and less understandable, but hey, it's *my* code and I can do whatever damn-fool thing I like! -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Tue, 17 Jul 2012 01:12:47 +, Steven D'Aprano wrote: It looks like Firebird implements the variety of ternary logical called Keene logic. Oops, I meant Kleene. -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Mon, 16 Jul 2012 13:28:14 -0400, Dennis Lee Bieber wrote: On 16 Jul 2012 02:38:35 GMT, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info declaimed the following in gmane.comp.python.general: On Sun, 15 Jul 2012 12:02:37 -0500, Andrew Berg wrote: Okay, I see the value in this, but I don't understand why None has a truth value. And this is exactly the sort of mental confusion that Laura Crichton warned about (see the link I included earlier). Would one rather have the behavior seen in SQL for Null? http://www.firebirdsql.org/file/documentation/reference_manuals/ user_manuals/Firebird-Null-Guide.pdf That's a 51 page document. I'm not sure I know which behaviour you are referring to. Seems to me that the Firebird NULL object is closer to a float NaN than to Python's None, except that Firebird treats comparisons with NULL as returning a NULL, while Python treats comparisons with NaN as True or False. Both behaviours are reasonable, but the Firebird behaviour seems to be more error-prone. Hey, let's turn the IF statement into tri-state logic... [...] I'm not sure if you're being sarcastic here or not. Ternary logic is perfectly reasonable, although I expect that it would be error-prone because programmers would forget the unknown clause all the time. It looks like Firebird implements the variety of ternary logical called Keene logic. Of course, ternary logic can always be re-written in binary terms. Assuming that UNKNOWN evaluates as false: if flag: true-clause else: if flag is UNKNOWN: unknown-clause else: false-clause -- Steven -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On 7/15/2012 3:28 PM, Terry Reedy wrote:
Because everything does (or should).
I can see how truth testing for empty values is convenient, but perhaps
objects should only have a truth value if explicitly given one -
particularly in cases where such a value wouldn't be obvious or the
obvious value isn't the actual one:
c = types.SimpleNamespace()
if c: print('c')
...
c
c.__dict__
{}
Would it not be reasonable to expect an empty namespace to have a truth
value of False since [] and friends do? It's a bit of a gray area for an
object defined by class C: pass, but this is *specifically intended*
to be a namespace. Why should things like functions or exceptions have
truth values?
Note: For those who aren't aware, types.SimpleNamespace was added in
3.3.0b1.
On a side note, I tend to do this:
x = some_list
try:
y = x.pop()
except IndexError:
do_something_else()
rather than:
if x:
y = x.pop()
else:
do_something_else()
but of course that only applies to empty lists/sets/related and not
0/0.0/None and only when I want something from the list/set/whatever.
--
CPython 3.3.0b1 | Windows NT 6.1.7601.17803
--
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Re: Implicit conversion to boolean in if and while statements
On Jul 15, 9:50 pm, Rick Johnson rantingrickjohn...@gmail.com wrote: On Sunday, July 15, 2012 11:19:16 AM UTC-5, Ian wrote: On Sun, Jul 15, 2012 at 4:56 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: (For the record, I can only think of one trap for the unwary: time objects are false at *exactly* midnight.) Ugh, that's irritating. I can't think of any scenario where I would ever want the semantics if timeval (is not midnight):. This reinforces the point that if you only want to test whether you have None, you should use is not None rather than relying on __bool__. I think this issue is not so much a bool test vs type test, but more an ambiguous syntax issue. If you know some English, its clear that if and while create bool contexts. [If you know English but have not studied logic the 'if/while' make sense whereas 'bool' is gobbledygook] The issue is not where the cast goes to -- this clearly is bool But where the cast comes from -- which requires tracing program-paths -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On 7/16/2012 7:43 PM, Steven D'Aprano wrote:
The existence of a jar or no jar is irrelevant to the question of how
many jellybeans there are. They are two different things, and therefore
need two different values. There are many ways to implement this.
I have a better real example, but I opted not to use it before since it
requires some explanation - IRC messages.
A client-to-server message has the basic form of b'COMMAND arguments
:message' (e.g. b'PRIVMSG #channel :hi guys!'). Some commands have no
message part because there is no message associated with it (e.g. b'JOIN
#channel') and there is at least one where there is a big difference
between a blank message (b'') and no message - b'TOPIC #channel' is a
request for the topic while b'TOPIC #channel :' clears the topic since
the part after the b':' is b'' (b'TOPIC #channel :Welcome to #channel'
sets the topic to Welcome to #channel). In my code, I would have an
object representing a message rather than parsing it multiple times. If
the message
attribute is not None, I send b'{command} {args} :{message}', otherwise
b'{command} {args}'. If I considered '' falsey, either I would require
all messages to have : (which would not actually be part of the
message) or have any request to view the topic as a channel op clear the
topic. This would apply to the server parsing the message as well. A few
other commands have messages optional as well, but they are not as
serious as TOPIC.
I could do:
if has_message:
send('{command} {args} :{message}')
else:
send('{command} {args}')
but then I'd have to make sure has_message stays accurate since message
won't necessarily be. Or maybe I could leave message undefined and catch
the appropriate exception. However, using None is the cleanest and most
obvious.
I know Rick likes to troll, but I do agree with him that if something:
for arbitrary objects can be ambiguous or confusing. I don't think
if/while must have True or False, but not every object has an obvious
truth value.
--
CPython 3.3.0b1 | Windows NT 6.1.7601.17803
--
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Re: Implicit conversion to boolean in if and while statements
On Tue, Jul 17, 2012 at 11:57 AM, Andrew Berg bahamutzero8...@gmail.com wrote:
I could do:
if has_message:
send('{command} {args} :{message}')
else:
send('{command} {args}')
but then I'd have to make sure has_message stays accurate since message
won't necessarily be. Or maybe I could leave message undefined and catch
the appropriate exception. However, using None is the cleanest and most
obvious.
I know Rick likes to troll, but I do agree with him that if something:
for arbitrary objects can be ambiguous or confusing. I don't think
if/while must have True or False, but not every object has an obvious
truth value.
Using None when '' is a valid token is the right thing to do (see
also, for instance, SQL's NULL, which is often used the same way). And
then you have gone away from the language's idea of whether a string
is truthy or not, so you get explicit:
if message is not None:
send('{command} {args} :{message}')
Easy! Or if the language went the other way (all strings are true),
it would be the other way around, you'd use if message!='' for the
other case. It's not a difficult problem.
Carry on bikeshedding. :)
ChrisA
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Re: Implicit conversion to boolean in if and while statements
On Mon, 16 Jul 2012 20:22:18 -0500, Andrew Berg wrote:
On 7/15/2012 3:28 PM, Terry Reedy wrote:
Because everything does (or should).
I can see how truth testing for empty values is convenient, but perhaps
objects should only have a truth value if explicitly given one -
particularly in cases where such a value wouldn't be obvious or the
obvious value isn't the actual one:
You have run into Python's default behaviour: objects are treated as
something by default. If you want them to represent nothing, you have to
explicitly code that case.
py o = object()
py bool(o)
True
Yet again, thinking about something versus nothing instead of true/false
makes the behaviour both obvious and correct: of course an object should
be treated as something (true-like) rather than nothing (false-like) by
default, it's an *object* is it not?
If you want your type to implement non-default semantics, such as
container semantics, then you need to code it.
c = types.SimpleNamespace()
if c: print('c')
...
c
c.__dict__
{}
Would it not be reasonable to expect an empty namespace to have a truth
value of False since [] and friends do? It's a bit of a gray area for an
object defined by class C: pass, but this is *specifically intended*
to be a namespace. Why should things like functions or exceptions have
truth values?
And this is a good life-lesson that any class called SimpleFoo will not
stay simple for long.
If you are right that SimpleNamespace should be treated as a container,
then it should implement container semantics. Since it doesn't, that is
either:
1) a bug; or
2) a triumph of laziness over correctness
I imagine though that the Python dev's answer will basically be #2: it
isn't a container, it just behaves a little bit like a container, except
when it doesn't kinda thing. But feel free to report it as a bug and see
what happens.
(This is not *entirely* wrong, because SimpleNamespace certainly doesn't
*claim* to be a container, nor does it expose the full container API. But
it should, even if that means it is no longer quite so simple.)
--
Steven
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Re: Implicit conversion to boolean in if and while statements
On Mon, Jul 16, 2012 at 12:03 AM, Steven D'Aprano steve+comp.lang.pyt...@pearwood.info wrote: On Sun, 15 Jul 2012 22:15:13 -0400, Devin Jeanpierre wrote: For example, instead of if stack: or if bool(stack):, we could use if stack.isempty():. This line tells us explicitly that stack is a container. isempty is not a container method. Your entire reply is predicated on this idea that I was talking about writing classes with this extra isempty method. No. I was talking about having isempty be part of the collection interface, and eliminating polymorphic bool conversion. If you were confused, instead of assuming I meant something patently absurd, you should have asked for a clarification. -- Devin -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Tue, Jul 17, 2012 at 2:18 PM, Ranting Rick rantingrickjohn...@gmail.com wrote: On Jul 16, 11:11 pm, Steven D'Aprano steve +comp.lang.pyt...@pearwood.info wrote: I imagine though that the Python dev's answer will basically be #2: it isn't a container, it just behaves a little bit like a container, except when it doesn't kinda thing. The emperor has no clothes! The Troll's New Point. ChrisA -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On Mon, 16 Jul 2012 20:57:43 -0500, Andrew Berg wrote:
I have a better real example, but I opted not to use it before since it
requires some explanation - IRC messages. A client-to-server message has
the basic form of b'COMMAND arguments :message' (e.g. b'PRIVMSG #channel
:hi guys!'). Some commands have no message part because there is no
message associated with it (e.g. b'JOIN #channel') and there is at least
one where there is a big difference between a blank message (b'') and no
message - b'TOPIC #channel' is a request for the topic while b'TOPIC
#channel :' clears the topic since the part after the b':' is b''
(b'TOPIC #channel :Welcome to #channel' sets the topic to Welcome to
#channel).
Okay, so you have two distinct nothing states when considering the
message part of an IRC command: the empty string, and missing.
That's okay. Floats have two zeroes (+0.0 and -0.0); complex numbers have
four. (Although they try hard to hide that distinction from you.)
There's nothing that says that you can only have a single falsey value in
a type, or that you might not sometimes wish to distinguish between
different false-like states. You need to distinguish between the many
different true-like messages, so you should not be surprised that you
need to distinguish between two false-like messages.
There are many ways to implement this. Here are just the most obvious:
1) a Command object where the message attribute is optional, but if
present, it is always a string;
2) a Command object where the message attribute is always present, but
can be a string or some non-string sentinel value (e.g. None);
3) a string, where the message attribute is determined by the location
of the colon, if any
4) a tuple with either two or three fields: (command, channel [,message])
In my code, I would have an object representing a message
rather than parsing it multiple times. If the message
attribute is not None, I send b'{command} {args} :{message}', otherwise
b'{command} {args}'.
Clear and obvious. Nothing wrong with that.
I could do:
if has_message:
send('{command} {args} :{message}')
else:
send('{command} {args}')
but then I'd have to make sure has_message stays accurate since message
won't necessarily be.
Yes, keeping a separate variable is a mug's game. Encapsulate it in the
Command object, and have the Command object responsible for keeping it in
sync (assuming it is mutable), or just make Command immutable and be done
with it.
Or maybe I could leave message undefined and catch
the appropriate exception. However, using None is the cleanest and most
obvious.
Yes it is. What's your point?
You've discovered a real-world situation where you can't collapse the
entire universe of valid values into just two, True and False, without
losing information. Did you think that this would be surprising?
Python developers often talk about interpreting objects in a boolean
context -- that's a pretty big hint that the semantics are to collapse
the value into two states. If you need three (or four, or fifty)
distinguishable states, then obviously boolean context will not solve
your problem. I never said it would.
--
Steven
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Re: Implicit conversion to boolean in if and while statements
On 7/16/2012 11:11 PM, Steven D'Aprano wrote: If you are right that SimpleNamespace should be treated as a container, then it should implement container semantics. Since it doesn't, that is either: 1) a bug; or 2) a triumph of laziness over correctness I imagine though that the Python dev's answer will basically be #2: it isn't a container, it just behaves a little bit like a container, except when it doesn't kinda thing. But feel free to report it as a bug and see what happens. I'm not saying it's necessarily wrong, but I do think it quacks a lot like a container, even though it isn't one, especially if you're listening for quacks instead of looking for ducks. -- CPython 3.3.0b1 | Windows NT 6.1.7601.17803 -- http://mail.python.org/mailman/listinfo/python-list
Re: Implicit conversion to boolean in if and while statements
On 7/16/2012 11:39 PM, Steven D'Aprano wrote: If you need three (or four, or fifty) distinguishable states, then obviously boolean context will not solve your problem. I never said it would. That is the impression I got from this statement: How you interpret some_variable = None depends on what some_variable represents. If some_variable represents number of jelly beans in a jar, then that should be 0 if there is no jar. But I guess you misunderstood (or were just picking at) the example. Of course I can (and do) explicitly use if x is not None when testing for None, but I don't want a bug being obscured because if x accepts an erroneous value that it interprets as truthy or falsey. I could be explicit when testing for things other than None, but apparently that's un-Pythonic. To put it in duck-typing terms, why should everything have to quack like True or False? Sure, I can see why 1 quacks like True or [] quacks like False, but I don't see why say, a Logger or function should quack like either. Should a Thread object be True if it's been started and False otherwise? If it truly is about something vs. nothing, why is a NameError (or AttributeError) raised when testing with an undefined variable? Being undefined quacks like nothing, doesn't it? -- CPython 3.3.0b1 | Windows NT 6.1.7601.17803 -- http://mail.python.org/mailman/listinfo/python-list
[issue7171] Add inet_ntop and inet_pton support for Windows
Atsuo Ishimoto ishim...@gembook.org added the comment: Implementation of inet_pton and inet_ntop by WSAAddressToStringA and WSAStringToAddressA for Windows. Conversion of IPv6 address might fail if IPv6 is not installed. Tested on Windows XP SP3 and Windows7. -- keywords: +patch nosy: +ishimoto Added file: http://bugs.python.org/file26392/issue7171.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue7171 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15317] Source installation sets incorrect permissions for Grammar3.2.3.final.0.pickle
Tomi Pieviläinen tomi.pievilainen+launch...@iki.fi added the comment: On Sat, Jul 14, 2012 at 12:44:46PM +, Éric Araujo wrote: Éric Araujo mer...@netwok.org added the comment: How did you configure and build? If you ran make as root it may explain this. Indeed I did do it as root for all steps. The umask for root was 022, however. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15317 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15337] The cmd module incorrectly lists help as an undocumented command
Changes by Raymond Hettinger raymond.hettin...@gmail.com: -- versions: -Python 3.2, Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15337 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14635] telnetlib uses select instead of poll - limited to FD_SETSIZE fds
Roundup Robot devn...@psf.upfronthosting.co.za added the comment: New changeset de229dde486b by Gregory P. Smith in branch '3.2': Fixes Issue #14635: telnetlib will use poll() rather than select() when possible http://hg.python.org/cpython/rev/de229dde486b New changeset 558e5ed678c3 by Gregory P. Smith in branch 'default': Fixes Issue #14635: telnetlib will use poll() rather than select() when possible http://hg.python.org/cpython/rev/558e5ed678c3 -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14635 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14790] use packaging in setup.py
Martin v. Löwis mar...@v.loewis.de added the comment: At the moment, it seems that this just won't happen. If a new attempt is made to integrate packaging with Python, this may or may not become an issue (e.g. whoever is doing the integration the next time might adapt setup.py from the beginning). So closing this as won't fix. -- priority: deferred blocker - resolution: - wont fix status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14790 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14635] telnetlib uses select instead of poll - limited to FD_SETSIZE fds
Changes by Gregory P. Smith g...@krypto.org: -- resolution: - fixed stage: - committed/rejected status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14635 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15233] atexit: guarantee order of execution of registered functions?
Raymond Hettinger raymond.hettin...@gmail.com added the comment: +1 for backport. There's no benefit to leaving ambiguity floating about, nor was there ever any intention for the behavior to have been different. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15233 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue12428] functools test coverage
Changes by Brian Thorne hardb...@gmail.com: -- nosy: +jackdied ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue12428 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15337] The cmd module incorrectly lists help as an undocumented command
Roundup Robot devn...@psf.upfronthosting.co.za added the comment: New changeset 076ae30e5dd0 by Raymond Hettinger in branch '2.7': Issue 15337: help() shown as undocumented http://hg.python.org/cpython/rev/076ae30e5dd0 -- nosy: +python-dev ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15337 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15337] The cmd module incorrectly lists help as an undocumented command
Changes by Raymond Hettinger raymond.hettin...@gmail.com: -- resolution: - fixed status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15337 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue12978] Figure out extended attributes on BSDs
koobs koobs.free...@gmail.com added the comment:
And to clarify the no-follow-symlinks case on FreeBSD:
extattr_{get,set,list,delete}_link system calls behave in the same way as
their _file counterparts, except that they do not follow sym-links. as per the
man page.
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[issue4130] Intel icc 9.1 does not support __int128_t used by ctypes
Stefan Krah stefan-use...@bytereef.org added the comment: I agree with Meador that this should be fixed upstream first. There's a thread here on libffi-discuss, with a patch but no conclusive answer: http://sourceware.org/ml/libffi-discuss/2012/msg00168.html -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4130 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4130] Intel icc 9.1 does not support __int128_t used by ctypes
Stefan Krah stefan-use...@bytereef.org added the comment: Ah, forget that: Alex has apparently already tested that patch. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4130 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15364] sysconfig confused by relative paths
New submission from Richard Oudkerk shibt...@gmail.com:
With unix, and a source build, sysconfig.get_config_var('srcdir') and
sysconfig.get_path('include') misbehave:
user@mint-vm ~/Repos/cpython $ cd /
user@mint-vm / $ ~/Repos/cpython/python
Python 3.3.0b1 (default:671894ae19a2, Jul 16 2012, 10:43:27)
[GCC 4.5.2] on linux
Type help, copyright, credits or license for more information.
import sysconfig
sysconfig.get_config_var('srcdir')
'/'
sysconfig.get_path('include')
'//Include'
The problem seems to be the else clause of
if 'srcdir' not in _CONFIG_VARS:
_CONFIG_VARS['srcdir'] = _PROJECT_BASE
else:
_CONFIG_VARS['srcdir'] = _safe_realpath(_CONFIG_VARS['srcdir'])
The else clause (in slightly modified form) was introduced in 356d0ea8ea34, and
it turns a relative path into an absolute path, using the current working
directory as a base.
For me, simply removing the line allows the absolute path to be calculated
correctly a few lines later on.
I don't know what problem 356d0ea8ea34 was intended to fix.
--
messages: 165581
nosy: sbt
priority: normal
severity: normal
stage: needs patch
status: open
title: sysconfig confused by relative paths
type: behavior
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[issue15170] Fix 64-bit building for buildbot scripts (2.7)
Stefan Krah stefan-use...@bytereef.org added the comment: Closing, since all 2.7 buildbots compile. -- resolution: - fixed stage: - committed/rejected ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15170 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15352] importlib.h should be regenerated when the marshaling code changes
Antoine Pitrou pit...@free.fr added the comment: Anyway, I am hitting another problem now -- _freeze_importlib is *not* idempotent. What do you mean with idempotent? Deterministic? -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15352 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15170] Fix 64-bit building for buildbot scripts (2.7)
Changes by Stefan Krah stefan-use...@bytereef.org: -- status: open - closed ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15170 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15171] Fix 64-bit building for buildbot scripts (3.2)
Stefan Krah stefan-use...@bytereef.org added the comment: David, do you have an idea why the XP-4 3.2 machine fails the compile? I can't reproduce this and I don't know if it's related to 334ff92a8483 or 177f93f0f5b9. -- nosy: +db3l ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15171 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15364] sysconfig confused by relative paths
Changes by Ned Deily n...@acm.org: -- nosy: +ronaldoussoren ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15364 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15365] Traceback reporting can fail if IO cannot be imported
New submission from Kristján Valur Jónsson krist...@ccpgames.com:
Reporting an error early in the python startup, before importing is properly
initialized, can be tricky.
For example, here:
if (PyImport_ImportFrozenModule(_frozen_importlib) = 0) {
Py_FatalError(Py_Initialize: can't import _frozen_importlib);
The problem is, that _Py_DisplaySourceLine will set an exception because it
cannot import the io module. And this will terminate the traceback output.
The attached patch aims to rectify it by ignoring errors from this api in
traceback.c
--
components: Interpreter Core
files: traceback.patch
keywords: patch
messages: 165585
nosy: kristjan.jonsson
priority: normal
severity: normal
status: open
title: Traceback reporting can fail if IO cannot be imported
type: behavior
versions: Python 3.3
Added file: http://bugs.python.org/file26393/traceback.patch
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[issue1492704] distinct error type from shutil.move()
Atsuo Ishimoto ishim...@gembook.org added the comment: Cleaned up the patch. Gennadiy added a test of shutil.move(), but SameFileError will be raised only if shutil.copy() was called. Am I missing something? -- nosy: +ishimoto Added file: http://bugs.python.org/file26394/issue1492704_new.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1492704 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue4130] Intel icc 9.1 does not support __int128_t used by ctypes
Alex Leach beamesle...@gmail.com added the comment: I hadn't tried the `long long` substitution before, but unfortunately I don't think that simple fix quite does the trick. I just checked out libffi from git, and made the following patch:- #$ diff -u ffi64.c ffi64.c.orig --- ffi64.c 2012-07-16 11:38:44.237255615 +0100 +++ ffi64.c.orig2012-07-16 11:38:34.681045084 +0100 @@ -38,7 +38,7 @@ #define MAX_SSE_REGS 8 #ifdef __INTEL_COMPILER -#define UINT128 long long +#define UINT128 __m128 #else #define UINT128 __int128_t #endif It compiles fine, but `make check` returns a lot of FAIL's, and a quite a few of the tests timeout. e.g. FAIL: libffi.special/unwindtest.cc -shared-libgcc -lstdc++ execution test WARNING: program timed out. It's probably also worth mentioning that I'm now using icc version 12.1.4 Cheers, Alex On Monday 16 Jul 2012 09:53:36 Stefan Krah wrote: Stefan Krah stefan-use...@bytereef.org added the comment: Ah, forget that: Alex has apparently already tested that patch. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4130 ___ -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue4130 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15238] shutil.copystat should copy Linux extended attributes
Stefan Krah stefan-use...@bytereef.org added the comment: The new test fails on the Fedora bot: http://buildbot.python.org/all/builders/AMD64%20Fedora%20without%20threads%203.x/builds/2881/steps/test/logs/stdio == FAIL: test_copyxattr (test.test_shutil.TestShutil) -- Traceback (most recent call last): File /home/buildbot/buildarea/3.x.krah-fedora/build/Lib/test/test_shutil.py, line 420, in test_copyxattr self.assertEqual(os.listxattr(src), ['user.the_value']) AssertionError: Lists differ: ['security.selinux', 'user.the... != ['user.the_value'] First differing element 0: security.selinux user.the_value First list contains 1 additional elements. First extra element 1: user.the_value - ['security.selinux', 'user.the_value'] + ['user.the_value'] -- nosy: +skrah ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15238 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15366] venv assumes header files in sys._home + '/Include'
New submission from Richard Oudkerk shibt...@gmail.com:
For Unix I follow the practice suggested in README of running configure from a
subdir of the main python directory, eg
mkdir release
cd release
../configure
make
But if I create a venv then I cannot use it to compile C extensions because the
include dirs are wrong, eg
running build
running build_ext
building 'demo' extension
gcc -pthread -Wno-unused-result -DNDEBUG -g -fwrapv -O3 -Wall
-Wstrict-prototypes -fPIC -I/home/user/Repos/cpython/release/Include
-I/home/user/Repos/cpython/release -c demo.c -o build/temp.linux-i686-3.3/demo.o
demo.c:1:20: fatal error: Python.h: No such file or directory
compilation terminated.
error: command 'gcc' failed with exit status 1
The problem seems to be that distutils.sysconfig.get_python_inc() assumes that
if sys._home is set (as it is in a virtual env) then the standard header files
can be found in sys._home + '/Include'.
But for my venv this is wrong, since sys._home is
/home/user/Repos/cpython/release and
/home/user/Repos/cpython/release/Include is empty. Instead get_python_inc()
should return /home/user/Repos/cpython/Include.
BTW, a seperate issue seems to be that ${venv}/include is not added to the list
of include dirs used when compiling.
--
components: Library (Lib)
messages: 165589
nosy: sbt, vinay.sajip
priority: normal
severity: normal
stage: needs patch
status: open
title: venv assumes header files in sys._home + '/Include'
type: behavior
versions: Python 3.3
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[issue15367] build_ext in a venv on Windows assumes pyconfig.h in sys.exec_prefix + '\PC'
New submission from Richard Oudkerk shibt...@gmail.com: On Windows I can't use a source build of Python to create a venv which will compile C extensions because pyconfig.h cannot be found. For example running build running build_ext building 'demo' extension creating build creating build\temp.win32-3.3 creating build\temp.win32-3.3\Release c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\BIN\cl.exe /c /nologo /Ox /MD /W3 /GS- /DNDEBUG -IC:\Repos\cpython\include -IC:\Users\oudkerk\myenv\PC /Tcdemo.c /Fobuild\temp.win32-3.3\Release\demo.obj demo.c C:\Repos\cpython\include\Python.h(8) : fatal error C1083: Cannot open include file: 'pyconfig.h': No such file or directory error: command 'c:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\BIN\cl.exe' failed with exit status 2 The problem seems to be with the following line in distutils/command/build_ext.py: self.include_dirs.append(os.path.join(sys.exec_prefix, 'PC')) Inside a venv, sys.exec_prefix is the venv directory. -- messages: 165590 nosy: sbt, vinay.sajip priority: normal severity: normal stage: needs patch status: open title: build_ext in a venv on Windows assumes pyconfig.h in sys.exec_prefix + '\PC' type: behavior versions: Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15367 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15238] shutil.copystat should copy Linux extended attributes
Hynek Schlawack h...@ox.cx added the comment: You can’t just compare the xattr because some (like security.*) can be only copied as root. IIRC they come from SELinux. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15238 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15352] importlib.h should be regenerated when the marshaling code changes
Antoine Pitrou pit...@free.fr added the comment: Le lundi 16 juillet 2012 à 05:42 +, Meador Inge a écrit : The order of 'co_cellvars', 'co_varnames', and 'co_freevars' can be different from compile to compile, thus the bytecode can be different from compile to compile (I am not sure if this is worth fixing). I don't know, but you could open an issue just for the record. People may be surprised if bytecode generation isn't deterministic. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15352 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1492704] distinct error type from shutil.move()
Changes by Antoine Pitrou pit...@free.fr: -- nosy: +hynek ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1492704 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15367] build_ext in a venv on Windows assumes pyconfig.h in sys.exec_prefix + '\PC'
Richard Oudkerk shibt...@gmail.com added the comment: The attached patch works for me. -- keywords: +patch Added file: http://bugs.python.org/file26395/build_ext.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15367 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15307] Patch for --symlink support in pyvenv with framework python
Ronald Oussoren ronaldousso...@mac.com added the comment: The test failure in test_osx_env is in itself fairly harmless because PYTHONEXECUTABLE is only used to ensure IDLE.app works correct, and IDLE.app doesn't use the pythonw executable and hence won't hit the code that special-cases the venv location. That said, the failure should be removed and points to a real issue in my patch: with my patch calculate_path replaces the value set by Py_SetProgramName and that is a real problem that could break 3th-party code without a good reason. I've attached v5 of the patch, this fixes the test_osx_env failure by moving the the code that uses __PYVENV_LAUNCHER__ to main.c (where Py_SetProgramName is called) -- Added file: http://bugs.python.org/file26396/venv-symlinks-v6.txt ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15307 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15352] importlib.h should be regenerated when the marshaling code changes
Meador Inge mead...@gmail.com added the comment: On Mon, Jul 16, 2012 at 5:20 AM, Antoine Pitrou rep...@bugs.python.org wrote: Anyway, I am hitting another problem now -- _freeze_importlib is *not* idempotent. What do you mean with idempotent? Deterministic? Whoops, yeah, deterministic. I got mixed up with my terminology. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15352 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15368] bytecode generation is not deterministic
New submission from Meador Inge mead...@gmail.com: Consider this small example (you might have to run sample program multiple times to see a difference): $ cat dis-closure.py import dis def adder(a, b): def add(): return a + b return add print(dis.dis(adder(1, 2).__code__)) $ ./python.exe dis-closure.py 5 0 LOAD_DEREF 0 (a) 3 LOAD_DEREF 1 (b) 6 BINARY_ADD 7 RETURN_VALUE None $ ./python.exe dis-closure.py 5 0 LOAD_DEREF 1 (a) 3 LOAD_DEREF 0 (b) 6 BINARY_ADD 7 RETURN_VALUE None The order of 'co_cellvars' and 'co_freevars' can be different from compile to compile, thus the bytecode can be different from compile to compile. This is due to the fact that these variable sets are managed with hashes and the ordering may come out different when the names in the hashes are given indexes (via 'dictbytype' in 'compile.c'). I am not sure if these are the only areas that causes bytecode generation to be non-deterministic. I found this behavior surprising. -- components: Interpreter Core messages: 165596 nosy: meador.inge priority: normal severity: normal stage: needs patch status: open title: bytecode generation is not deterministic type: behavior versions: Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15368 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15352] importlib.h should be regenerated when the marshaling code changes
Meador Inge mead...@gmail.com added the comment: On Mon, Jul 16, 2012 at 7:13 AM, Antoine Pitrou rep...@bugs.python.org wrote: I don't know, but you could open an issue just for the record. People may be surprised if bytecode generation isn't deterministic. Yeah, I was somewhat surprised and it took some digging to figure out exactly what was changing. Opened issue15368 to track this. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15352 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15366] venv assumes header files in sys._home + '/Include'
Richard Oudkerk shibt...@gmail.com added the comment: The attached patch seems to fix the problem. -- keywords: +patch Added file: http://bugs.python.org/file26397/distutils-sysconfig.patch ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15366 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1492704] distinct error type from shutil.move()
Éric Araujo mer...@netwok.org added the comment: Thanks. Can you clarify what behavior changed compared to the previous patch? From the doc it looks like shutil.move now always raises SameFileError, whereas the previous patch said that on Unix it depended on the semantics of os.rename. The patch has some very minor issues like extraneous whitespace in the docs, but they can be fixed by the person committing. -- assignee: eric.araujo - keywords: +needs review stage: test needed - patch review versions: +Python 3.4 -Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1492704 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15368] bytecode generation is not deterministic
Brett Cannon br...@python.org added the comment: I might come to regret asking this, but so what? Is this actually causing you issues, or are you literally just finding this behavior surprising and that's it? I mean we could simply sort the tuples, but I don't know what kind of performance hit that would cause. -- nosy: +brett.cannon ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15368 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15368] bytecode generation is not deterministic
Meador Inge mead...@gmail.com added the comment: On Mon, Jul 16, 2012 at 8:11 AM, Brett Cannon rep...@bugs.python.org wrote: I might come to regret asking this, but so what? Is this actually causing you issues, or are you literally just finding this behavior surprising and that's it? I noticed it in the context of working on issue15352. There are still a few issue in the build system where 'importlib.h' isn't regenerated when it needs to be (e.g. when the marshaling code is changed). When investigating that issue I noticed that trivial changes (e.g. `touch _bootstrap.py`) can cause differences in 'importlib.h'. Those differences are mainly due to the cell and free var indexes being reordered. Since the bytecode generation isn't deterministic, there can be some noisy diffs in your working copy when mucking around with the files related to the frozen importlib. Thus if we ever wanted to just always generate importlib.h because we can't be sure which changed source files should cause importlib.h to be regenerated, then the non-determinism would be a real annoyance. That is the only concrete issue I currently am aware of. This issue may not actually be worth addressing, but I felt it was worthy of discussion. -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15368 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue14644] test_logging failure on OS X Tiger
Ronald Oussoren ronaldousso...@mac.com added the comment: I get failures for the same test on my machine running OSX 10.7, the machine is fairly overloaded right now because I'm running a large VM in the background. Increasing the timeout from 5.0 to 15.0 seconds ensures that the test passes. -- nosy: +ronaldoussoren ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue14644 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue9102] pybench: Cannot compare 2.x and 3.x benchmarks
Changes by Florent Xicluna florent.xicl...@gmail.com: -- versions: +Python 3.4 -Python 3.2 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue9102 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue15369] pybench and test.pystone poorly documented
New submission from Florent Xicluna florent.xicl...@gmail.com: The benchmarking tools pystones and pybench which are shipped with the Python standard distribution are not documented. The only information is in the what's-new for Python 2.5: http://docs.python.org/dev/whatsnew/2.5.html?highlight=pybench#new-improved-and-removed-modules IMHO, they should be mentioned somewhere in the HOWTOs, the FAQ or the standard library documentation (Development Tools or Debugging and Profiling) -- assignee: docs@python components: Benchmarks, Documentation messages: 165603 nosy: docs@python, flox priority: normal severity: normal status: open title: pybench and test.pystone poorly documented type: behavior versions: Python 3.3 ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue15369 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
[issue1492704] distinct error type from shutil.move()
Atsuo Ishimoto ishim...@gembook.org added the comment: Behavior is not changed at all. I fixed test_shutil.py to test if SameFileError is raised in shutil.copy() instead of shutil.move(). -- ___ Python tracker rep...@bugs.python.org http://bugs.python.org/issue1492704 ___ ___ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
