Accessing a method from within its own code
Hi, I was wondering if there was a shorthand way to get a reference to a method object from within that method's code. Take this code snippet as an example: import re class MyClass(object): def find_line(self, lines): if not hasattr(MyClass.do_work, matcher): MyClass.do_work.matcher = re.compile(\d - (.+)) for line in lines: m = MyClass.do_work.matcher.match(line) if m: return m.groups() Here, I have a method which uses a regular expression object to find matches. I want the regexp object to be tied to the function, but I don't want to have to recreate it every time the function is called (I am aware that regexp objects are cached, avoiding this problem, but I'm just using this as an example for what I want to know), so I've added it to the method object as an attribute and create it only if it doesn't exist. However, typing out Classname.MethodName.variablename everytime is pretty long and susceptible to refactoring issues, so I was wondering if there was a way in Python that I am missing which allows you to reference the method that the code is in (like __module__ gives a reference to the parent module). Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: Accessing a method from within its own code
I suspect that the inspection module has your answer, but that it'll be bulkier, and much slower than just doing what you're doing already. Hmm. Yeah, it does appear to be bulky. I don't think it's really any more use than what I'm doing already. Why not use the default arguments gimmick? Since this cached item is to have a module lifetime, it'd be desirable to create it when the method is being defined, which is exactly what default arguments do. I've a few different ways of emulating static function variables from C/Java and the function/method attribute one is easily the one that appeals most to my sensibilities. I find the default arguments gimmick to be a gimmick. It's co-opting a piece of functionality for something it doesn't seem like it was originally intended for and as a consequence is less readable (to my eyes). The only problem with the function/method way is that it gets rather verbose when you are dealing with a user-defined method and have to give the class name and method name and it's also a bit of a pain for moving code around when refactoring. You ever wish there was more to python scoping than just locals(), globals() and __builtins__? Like a method's class's scope too? That's where I am at with this. -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: sorted() erraticly fails to sort string numbers
2009/4/30 Lie Ryan lie.1...@gmail.com container[:] = sorted(container, key=getkey) is equivalent to: container.sort(key=getkey) Equivalent, and in fact better since the sorting is done in-place instead of creating a new list, then overwriting the old one. Not when, as pointed out by uuid, container is not list-like (at least as far as the sort() method goes). :) Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Reading an exact number of characters from input
Hi, How would I use python to simply read a specific number of characters from standard input? raw_input() only returns when the user inputs a new line (or some other special character). I tried import sys sys.stdin.read(15) and that *returns* up to 15 characters, but it keeps accepting input (and doesn't return) until I press Enter. My initial thoughts are that a function like C's fgetc would be the easiest way to do it, but I haven't been able to find an equivalent in my google search, so I was wondering if anyone here might have some ideas. What say you? Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Introducing Python to others
Hi, As our resident python advocate, I've been asked by my team leader to give a bit of a presentation as an introduction to python to the rest of our department. It'll be less than an hour, with time for taking questions at the end. There's not going to be a whole lot of structure to it. First, I'm going to open up a python terminal and show them how the interpreter works and a few basic syntax things and then a file .py files (got to show them that python's indenting structure is not something to be afraid of :P). I think I'll mostly show things in the order that they appear in the python tutorial (http://docs.python.org/tutorial/). My question to you, dear python-list, is what suggestions do you have for aspects of python that I should show them to make them maybe think that python is better than what they are using at the moment. All of the audience will be experienced (4+ years) programmers, almost all of them are PHP developers (2 others, plus myself, work in C, know C#, perl, java, etc.). Because of this, I was thinking of making sure I included exceptions and handling, the richness of the python library and a pointing out how many modules there were out there to do almost anything one could think of. Anything else you think could make PHP developers starting think that python is a better choice? If I were to do a (very) short demonstration one web framework for the PHP devs, what should I use? CherryPy (seems to be the easiest), Django (seems to be the biggest/most used), or something else? Any other suggestions for a possible wow reaction from an audience like that? Thanks, Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: Introducing Python to others
Thanks for all your replies. A lot of very strong answers :) 2009/3/26 Mensanator mensana...@aol.com: What would you have to do to make this work? x+x+x # expecting [3,6] [2, 4, 1, 2] What's happening is that the call to map() is returning a list object. So after it calculates the first x+x, you are left with the equivalent of: [6, 6] + x Because the list object is on the left, it's __add__() function is called, which appends x to [6,6]. Instead, convert the list returned by map to a Vector before returning it. Like so: class Vector(list): ... def __add__(self, other): ... return Vector(map(add, self, other)) ... x = Vector([3,3]) x+x+x [9, 9] -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: Run a python script as an exe and run a new process from it
2009/2/27 venutaurus...@gmail.com venutaurus...@gmail.com: Thanks for the reply,, I am trying to use the above application using psexec()in command line.But it failed returning the error message exited with error code 255. But when I ran the application normally it worked fine.Do I need to add anything to my python script(either the main one or the script which is calling it) to make it work. I don't have any experience with psexec, so I'm not sure if I can help you with that. I assume this means that you are trying to run the script on a remote computer? (Elsewise, why use psexec?) I took a look at it though and it seems that it always exits with *some* error code. I think it's more usual for that error code to be zero, though (it does when I run it on my machine). You might try psexec start script1.py, which might work if you've successfully set Explorer to run .py files with python.exe when you double-click on them. psexec python script1.py will work if the python.exe is in the correct path. You can also specify the full path to your python.exe. if you know it e.g.: psexec C:\python25\python.exe script1.py -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: Run a python script as an exe and run a new process from it
Try this as an outline: script1.py from subprocess import Popen if __name__ == '__main__': scriptname = script2.py Popen(python %s % scriptname, shell=True) print I'm done script2.py from time import sleep if __name__ == '__main__': while (True): print waiting.. sleep(2) ### If you install python using the Windows Installer (.exe), it should set up .py files to be opened by python when double-clicking on them. Alternatively, you can right-click on your .py file and go to Open With... then choose program, then click Browse..., you can Browse to the python executable, so Explorer will use it to open .py files when you double-click on them. As someone else mentioned there is also a py2exe program. Google it. 2009/2/26 venutaurus...@gmail.com venutaurus...@gmail.com: Hello all, I've a strange requirement where I need to run a python script just as we run an exe (by double clicking through windows explorer or by typing the script name at command prompt). In that process I should be able to execute another python script in such a way that, the second script should continue running but the main one should terminate without effecting the second one. My requirement may be little confusing so please get back if you didn't understand what I meant above. Thank you, Venu. -- http://mail.python.org/mailman/listinfo/python-list -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: Byte type?
2009/2/24 John Nagle na...@animats.com: Martin v. Löwis wrote: Please don't call something dumb that you don't fully understand. It's offenses the people who have spent lots of time developing Python -- personal, unpaid and voluntary time! Some of the people involved are on Google's payroll. Uh, what does that have to do with anything? It would only be relevant if you are saying that Google is paying them to do the work (so not just on their payroll). More importantly, it's also only relevant if ALL the people contributing are being paid by Google to do the work, which I'm pretty sure is not the case. There are people are spending lots of personal, unpaid and voluntary time developing Python. Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I declare global vars or class vars in Python ?
2009/2/20 Bruno Desthuilliers bruno.42.desthuilli...@websiteburo.invalid: Note that while you *can* do direct access to the implementation attribute (here, '_A' for property 'A'), you don't *need* to so (and usually shouldn't - unless you have a very compelling reason). Interesting. Why shouldn't you? I haven't used the property() function before and probably have no call to, but when you say usually shouldn't, what is there against it? -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I declare global vars or class vars in Python ?
2009/2/20 Bruno Desthuilliers bruno.42.desthuilli...@websiteburo.invalid: Interesting. Why shouldn't you? I haven't used the property() function s/function/object/ Nice try, but what I wrote was what I intended to say: http://docs.python.org/library/functions.html#property For all I know I could have used property objects several times in modules :) The case is that the whole point of using a computed attribute is to perform some computation on the value. IOW, except for a couple corner cases, only the accessors should directly access the implementation(s) attributes(s). And of course, like for any other GoldenRule(tm), it's not meant to be blindly followed. It's just that most of the times, going thru the accessors is really what you want - even from within the class code. Hmm, it doesn't seem to me like it's much of a big deal, for it to described as anything like a GoldenRule or to advise against its overuse. You use it when its appropriate and don't use it when you it's not, like any other feature. Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I declare global vars or class vars in Python ?
2009/2/20 Bruno Desthuilliers bruno.42.desthuilli...@websiteburo.invalid: Check by yourself: import inspect inspect.isfunction(property) False Using this, every single builtin function returns False. That's a pretty limited definition to be being pedantic over, especially when they are in the Built-in Functions section of the manual. property() property object at 0xb7cbc144 I never said that calling it didn't return a property object :) property type 'property' So it's a type. I think I didn't make such a bad error on my part. My intent in what I was saying was to indicate that I hadn't created a property type. It's fair enough to consider type constructors as functions given how they are listed as such by the python documentation. I don't think that your correction was much help, unless you just want to say that everything is an object. Maybe you'd be right, but it's not much use to use the term that way, imo shrug dir(property) ['__class__', '__delattr__', '__delete__', '__doc__', '__get__', '__getattribute__', '__hash__', '__init__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__set__', '__setattr__', '__str__', 'fdel', 'fget', 'fset'] Doesn't prove a whole lot. So types have attributes... So do functions: def myfunc(): ... pass ... dir(myfunc) ['__call__', '__class__', '__delattr__', '__dict__', '__doc__', '__get__', '__getattribute__', '__hash__', '__init__', '__module__', '__name__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__str__', 'func_closure', 'func_code', 'func_defaults', 'func_dict', 'func_doc', 'func_globals', 'func_name'] Hmm, it doesn't seem to me like it's much of a big deal, for it to described as anything like a GoldenRule One could say the same for each and any of the usual GoldenRules(tm). Not really. To do so would be over-generalising and not useful to discussion I guess it's your pedantry that I'm questioning. Something like don't use goto's works as a GoldenRule because it's been observed that without it, people start using goto statements in places where it's not really appropriate. When you said that [you] usually shouldn't [use properties] - unless you have a very compelling reason, your tone implied that properties are easy to misuse and tend to be. Not being familiar with properties and seeing them as being pretty harmless, I was intrigued by this, which is why I asked for an explanation. Your explanation seems to show that your tone was likely to be more personal bias than any real issue with properties. Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I declare global vars or class vars in Python ?
Use the global statement. http://docs.python.org/reference/simple_stmts.html#the-global-statement A working example based on your pseudocode would be: def getA(): global A return A def getB(): global B return B def setA(value): global A A = value def setB(value): global B B = value def main(): setA(5) setB(6) print getA() print getB() if __name__ == '__main__': main() # Although honestly, I think you'd be best not coding like that (with gets and sets and all) in python. Paddy 2009/2/17 Linuxguy123 linuxguy...@gmail.com: How do I do this in Python ? # declare A,B function getA return A function getB return B function setA(value) A = value function setB(value) B = value main() getA getB dosomething setA(aValue) setB(aValue) The part I don't know to do is declare the variables, either as globals or as vars in a class. How is this done in Python without setting them to a value ? Thanks -- http://mail.python.org/mailman/listinfo/python-list -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: How do I declare global vars or class vars in Python ?
2009/2/17 MRAB goo...@mrabarnett.plus.com: It isn't possible to have an uninitialised variable. If it doesn't have a value then it doesn't exist. True, but you can use the global statement to refer to the variable within a function and read from the variable there, without it being already initialised in the module. Of course, if you try to call that function before the global has been initialised, python will complain [and rightly so :)] Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
Re: Pythonic way to determine if a string is a number
2009/2/16 Python Nutter pythonnut...@gmail.com: silly me, forgot to mention build a set from digits + '.' and use that for testing. Cheers, PN 2009/2/16 Python Nutter pythonnut...@gmail.com: Type casting seems to be the wrong way to go about this. teststring = '15719' teststring.isdigit() returns True That takes care of integers. from string import digits digits '0123456789' now you have all the digits and you can do set testing in your logic to see if the teststring has anything in digits A dumb way to test is alphanumeric teststring2 = '105.22' teststring2.isalnum() returns True now you can go on from there and test to further to eliminate 'abcd385laf8' which on alnum() also returns true. Hmmm, this doesn't seem right to me. Unless I'm missing something, won't your code think that 123.123.123 is numeric? What about scientific or engineering notation with exponents? What's wrong with using python's own casting rules (given that you are trying to emulate the way python behaves? Or, alternatively, using a regular expression (as Nick Craig-Wood did). Given these solutions, type-conversion and catching the ValueError appears, to me, to be correct, the most concise, and the most readable solution. Of course, if you want to use your own set of rules for number encoding, then building your own regular expression would seem to be the right way to go. Paddy -- Ray, when someone asks you if you're a god, you say YES! -- http://mail.python.org/mailman/listinfo/python-list
