Builtn super() function. How to use it with multiple inheritance? And why should I use it at all?
Hi! I have two super classes: class SuperClass1(object): def __init__(self, word): print word class SuperClass2(object): def __init__(self, word, word2): print word, word2 Also I have subclass of these classes: class SubClass(SuperClass1, SuperClass2): def __init__(self): pass I have two questions. 1) Inside __init__ of SubClass how can I firstly call __init__ of SuperClass1, and then __init__ of SuperClass2, using builtin super() function. 2) Why should I use super() at all, if it is very easy to call methods of super class like this: class SubClass(SuperClass1, SuperClass2): def __init__(self): SuperClass1.__init__(self, 'Python') SuperClass2.__init__(self, 'Hello', 'world') Thanks in advance. -- http://mail.python.org/mailman/listinfo/python-list
Re: Builtn super() function. How to use it with multiple inheritance? And why should I use it at all?
On Jul 24, 11:20 am, Raymond Hettinger raymond.hettin...@gmail.com
wrote:
On Jul 24, 12:47 am, Lacrima lacrima.ma...@gmail.com wrote:
Hi!
I have two super classes:
class SuperClass1(object):
def __init__(self, word):
print word
class SuperClass2(object):
def __init__(self, word, word2):
print word, word2
Also I have subclass of these classes:
class SubClass(SuperClass1, SuperClass2):
def __init__(self):
pass
I have two questions.
1) Inside __init__ of SubClass how can I firstly call __init__ of
SuperClass1, and then __init__ of SuperClass2, using builtin super()
function.
I would write it like this:
class SuperClass1(object):
def __init__(self, **kwds):
word = kwds.pop('word')
print word
super(SuperClass1, self).__init__(**kwds)
class SuperClass2(object):
def __init__(self, **kwds):
word1 = kwds.pop('word1')
word2 = kwds.pop('word2')
print word1, word2
super(SuperClass2, self).__init__(**kwds)
class SubClass(SuperClass1, SuperClass2):
def __init__(self, **kwds):
super(SubClass, self).__init__(**kwds)
SubClass(word='Python', word1='Hello', word2='World')
2) Why should I use super() at all, if it is very easy to call methods
of super class like this:
class SubClass(SuperClass1, SuperClass2):
def __init__(self):
SuperClass1.__init__(self, 'Python')
SuperClass2.__init__(self, 'Hello', 'world')
That works just fine in this case.
The challenge arises in diamond diagrams
such as A-B A-C B-D C-D where both B and C
are written independently of D and both need to call
A's __init__ but that method should only be called
once (not once by B and again by C).
In that case, the super() pattern shown above will
let each parent's method be called exactly once
and guarantee that parents are called before grandparents
and guarantee that the left-to-right ordering of multiple
bases is respected.
Raymond
Hi, Raymond!
Thank you for your answer.
Some things are still not clear. Your example works great. But if I
remove super(SuperClass1, self).__init__(**kwds) from SuperClass1's
__init__, the example stops working. That is when I instantiate
SubClass only __init__ of SuperClass1 is called and __init__ of
SuperClass2 is omitted, i.e. only 'Python' is printed. Why is it so?
So as I understand every parent should necessarily call super() at the
end of its __init__ method in order for things to work properly.
But what if SuperClass1 is from third party library? Then I can't
modify it to follow this convention, that is when I instantiate my
SubClass only __init__ from SuperClass1 will be called, and __init__
from SuperClass2 will be omitted.
How to deal with that?
My post is quite intricate, but this is because of my English. Sorry.
Looking forward for help. Thank you.
--
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String Formatting Operations for decimals.
Hello! I need to format a decimal (floating point) number in the following way: 10 results in '10' 10.5 results in '10.5' 10.50 results in '10.5' 10.5678 results in 10.57 How can I achieve this using standard Python string formatting operations? Something like '%.2f' works almost as expected: '%.2f' % 10.5 '10.50' '%.2f' % 10.5678 '10.57' '%.2f' % 10 '10.00' But I always need trailing zeros to be excluded, i.e. 10.5 should result in '10.5' (not '10.50'), and 10 should result in '10' (not '10.00'). So how can I do this? Sorry for my English. Thanks in advance. with regards, Maxim -- http://mail.python.org/mailman/listinfo/python-list
Re: String Formatting Operations for decimals.
Hello, Chris!
Thanks for your really quick reply! It works!
On 1 April 2010 12:14, Chris Rebert c...@rebertia.com wrote:
On Thu, Apr 1, 2010 at 2:08 AM, Lacrima lacrima.ma...@gmail.com wrote:
Hello!
I need to format a decimal (floating point) number in the following
way:
10 results in '10'
10.5 results in '10.5'
10.50 results in '10.5'
10.5678 results in 10.57
How can I achieve this using standard Python string formatting
operations?
Something like '%.2f' works almost as expected:
'%.2f' % 10.5
'10.50'
'%.2f' % 10.5678
'10.57'
'%.2f' % 10
'10.00'
But I always need trailing zeros to be excluded, i.e. 10.5 should
result in '10.5' (not '10.50'), and 10 should result in '10' (not
'10.00').
So how can I do this?
('%.2f' % 10).rstrip('0').rstrip('.')
Cheers,
Chris
--
http://blog.rebertia.com
--
with regards,
Maxim
--
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Re: Advanced Python Programming Oxford Lectures [was: Re: *Advanced* Python book?]
On Mar 26, 10:22 am, Michele Simionato michele.simion...@gmail.com wrote: On Mar 25, 2:24 pm, Michele Simionato michele.simion...@gmail.com wrote: On Mar 25, 1:28 pm, Ethan Furman et...@stoneleaf.us wrote: Michele, Was wondering if you'd had a chance to re-post your lectures -- just did a search for them and came up empty, and I would love to read them! Many thanks in advance! Oops, I forgot! I will try to make them available soon. Here they are:http://www.phyast.pitt.edu/~micheles/oxford-lectures.zip Hello, Michele! Thanks a lot for posting!!! -- http://mail.python.org/mailman/listinfo/python-list
Can't install ssl for Python2.5
Hello!
I use Ubuntu 9.10 Karmic Koala. It has Python 2.6 as default
installation.
And I installed Python 2.5 alongside (for the need of Google
AppEngine). But it seems like my Python 2.5 installation lacks ssl
support. I can't import ssl and starting appengine server fails with
'module' object has no attribute 'HTTPSHandler'.
So I tried to install this: http://pypi.python.org/pypi/ssl/1.15
But it failed with a very strange error:
sudo easy_install-2.5 ssl
-
Searching for ssl
Reading http://pypi.python.org/simple/ssl/
Reading http://docs.python.org/dev/library/ssl.html
Best match: ssl 1.15
Downloading
http://pypi.python.org/packages/source/s/ssl/ssl-1.15.tar.gz#md5=81ea8a1175e437b4c769ae65b3290e0c
Processing ssl-1.15.tar.gz
Running ssl-1.15/setup.py -q bdist_egg --dist-dir /tmp/easy_install-
Kd839q/ssl-1.15/egg-dist-tmp-QCIl6J
looking for /usr/include/openssl/ssl.h
looking for /usr/local/ssl/include/openssl/ssl.h
looking for /usr/include/krb5.h
looking for /usr/kerberos/include/krb5.h
error: Setup script exited with error: SandboxViolation: open('/usr/
local/lib/python2.5/test/test_ssl.py', 'wb') {}
The package setup script has attempted to modify files on your system
that are not within the EasyInstall build area, and has been aborted.
This package cannot be safely installed by EasyInstall, and may not
support alternate installation locations even if you run its setup
script by hand. Please inform the package's author and the
EasyInstall
maintainers to find out if a fix or workaround is available.
-
I don't know how to solve this problem and I am looking forward for
help.
Thanks in advance.
with regards,
Maxim.
--
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Re: Can't install ssl for Python2.5
On Mar 10, 11:23 pm, Martin v. Loewis mar...@v.loewis.de wrote: I don't know how to solve this problem and I am looking forward for help. Try running python setup.py install directly, after downloading and unpacking the package. Regards, Martin Thanks a lot! It helped! -- http://mail.python.org/mailman/listinfo/python-list
Using mock library (written by Michael Foord)
Hello!
I use mock library http://www.voidspace.org.uk/python/mock/. There is
no user group for the library, so I post in comp.lang.python and hope
that people who use it will help me.
The library allows to patch objects, using patch decorator. Patching
is done only within the scope of the function. So if I have a lot of
tests that need specific object to be patched I have to specify the
same decorator for each test method:
class TestSomething(unittest.TestCase):
@patch('module.Class', spec = True)
def test_method1(self, MockClass):
Class()
self.assertEquals(MockClass.called)
@patch('module.Class', spec = True)
def test_method2(self, MockClass):
Class()
MockClass.assert_called_with('foo')
@patch('module.Class', spec = True)
def test_method3(self, MockClass):
foo = Class()
self.assertRaises(AttributeError, foo.some_method)
# and more ...
So for every test method I always do the same patching! How can I
avoid this?
Thanks in advance.
Sorry if my English isn't proper enough.
With regards,
Maxim.
--
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Re: Which mock library do you prefer?
On Feb 18, 3:20 am, Ben Finney ben+pyt...@benfinney.id.au wrote:
Lacrima lacrima.ma...@gmail.com writes:
Right, isolation [of test cases] is essential. But I can't decide to
which extent I should propagate isolation.
You used “propagate” in a sense I don't understand there.
For example, in Python Testing: Beginner's Guide by Daniel Arbuckle,
author suggests that if you do unittesting you should isolate the
smallest units of code from each other.
I'm not sure what the author means, but I would say that as it stands
that advice is independent of what testing is being done. In all cases:
* Make your code units small, so each one is not doing much and is easy
to understand.
* Make the interface of units at each level as narrow as feasible, so
they're not brittle in the face of changes to the implementation.
For example, if you have a
class:
Class SomeClass(object):
def method1(self):
return 5
def method2(self):
return self.method1 + 10
According to the book, if you want to test method2, you should isolate
it from method1 and class instance('self').
I don't really know what that means.
Remember that each test case should not be “test method1”. That is far
too broad, and in some cases too narrow. There is no one-to-one mapping
between methods and unit test cases.
Instead, each test case should test one true-or-false assertion about
the behaviour of the code. “When we start with this initial state (the
test fixture), and perform this operation, the resulting state is that”.
It makes a lot of sense to name the test case so the assertion being
made *is* its name: not ‘test frobnicate’ with dozens of assertions, but
one ‘test_frobnicate_with_valid_spangulator_returns_true’ which makes
that assertion, and extra ones for each distinct assertion.
The failure of a unit test case should indicate *exactly* what has gone
wrong. If you want to make multiple assertions about a code unit, write
multiple test cases for that unit and name the tests accordingly.
This incidentally requires that you test something small enough that
such a true-or-false assertion is meaningful, which leads to
well-designed code with small easily-tested code units. But that's an
emergent property, not a natural law.
Currently, I don't create mocks of units if they are within the same
class with the unit under test. If that is not right approach, please,
explain what are best practices... I am just learning TDD..
In the fixture of the unit test case, create whatever test doubles are
necessary to put your code into the initial state you need for the test
case; then tear all those down whatever the result of the test case.
If you need to create great honking wads of fixtures for any test case,
that is a code smell: your code units are too tightly coupled to
persistent state, and need to be decoupled with narrow interfaces.
The Python ‘unittest’ module makes this easier by letting you define
fixtures common to many test cases (the ‘setUp’ and ‘tearDown’
interface). My rule of thumb is: if I need to make different fixtures
for some set of test cases, I write a new test case class for those
cases.
--
\ “Following fashion and the status quo is easy. Thinking about |
`\ your users' lives and creating something practical is much |
_o__) harder.” —Ryan Singer, 2008-07-09 |
Ben Finney
Hi, Ben!!!
Sorry for too late reply!!!
Thank you very much for sharing your experience! I still have to grasp
a lot in TDD.
--
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Re: Which mock library do you prefer?
On Feb 16, 7:38 pm, Phlip phlip2...@gmail.com wrote: This paper _almost_ gets the idea:http://www.netobjectives.com/download/Code%20Qualities%20and%20Practi... Do you run your tests after the fewest possible edits? Such as 1-3 lines of code? Hi! I run my tests all the time (they almost replaced debugger in my IDE). But there are times, when I can't just run tests after 1-3 lines of code. For example, I am developing an application that talks to some web service. One of methods of a class, which implements API for a given web service, should parse xml response from web service. At first, I hardcoded returned values, so that they looked like already parsed. But further, additional tests forced me to actually operate with sample xml data instead of hardcoded values. So I created sample xml file that resembled response from server. And after that I can't just write 1-3 lines between each test. Because I need to read() the file and sort it out in a loop (at least 6-9 lines of code for small xml file). And only after this procedure I run my tests with the hope that they all pass. Maybe it's not proper TDD, but I can't figure out how to reduce period between running tests in a case above. -- http://mail.python.org/mailman/listinfo/python-list
Re: Which mock library do you prefer?
On Feb 16, 10:30 pm, Ben Finney ben+pyt...@benfinney.id.au wrote:
Lacrima lacrima.ma...@gmail.com writes:
And I have already refused to write totally isolated tests, because it
looks like a great waste of time.
It only looks like that until you chase your tail in a long, fruitless
debugging session because (you later realise) the behaviour of one test
is being affected by another. Test isolation is essential to ensure that
your tests are doing what you think they're doing.
--
\ “A ‘No’ uttered from deepest conviction is better and greater |
`\ than a ‘Yes’ merely uttered to please, or what is worse, to |
_o__) avoid trouble.” —Mohandas K. Gandhi |
Ben Finney
Hi!
Right, isolation is essential. But I can't decide to which extent I
should propagate isolation.
For example, in Python Testing: Beginner's Guide by Daniel Arbuckle,
author suggests that if you do unittesting you should isolate the
smallest units of code from each other. For example, if you have a
class:
Class SomeClass(object):
def method1(self):
return 5
def method2(self):
return self.method1 + 10
According to the book, if you want to test method2, you should isolate
it from method1 and class instance('self').
Other books are not so strict...
And what should I follow as newbie?
Currently, I don't create mocks of units if they are within the same
class with the unit under test. If that is not right approach, please,
explain what are best practices... I am just learning TDD..
with regards,
Maxim
--
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Re: Which mock library do you prefer?
On Feb 16, 2:17 am, Ben Finney ben+pyt...@benfinney.id.au wrote: Lacrima lacrima.ma...@gmail.com writes: Minimock has wider usage and community, but I have some troubles using it. Maybe I am wrong, but with minimock you always have to keep track the order of imports in your test modules. Well, may be I just don't understand fully how minimock works. I'm not sure why you think you need to keep track of the order of imports. Simply set up the mocks as you want them, in your fixtures; then, when tearing down your fixtures, use ‘minimock.restore()’ to restore the affected namespaces to their initial state. -- \ “… one of the main causes of the fall of the Roman Empire was | `\ that, lacking zero, they had no way to indicate successful | _o__) termination of their C programs.” —Robert Firth | Ben Finney Hi Ben! See these two topics: http://groups.google.com/group/minimock-dev/browse_thread/thread/bcbb3b7cc60eb96f http://groups.google.com/group/minimock-dev/browse_thread/thread/c41cd996735ea1a6 There are special cases, which you have to be aware of, if you use minimock. -- http://mail.python.org/mailman/listinfo/python-list
Re: Which mock library do you prefer?
On Feb 15, 9:56 pm, Phlip phlip2...@gmail.com wrote: Lacrima wrote: Thanks for your reply! Isn't what you are talking about integration tests? And unit tests should be fully isolated? So even for method 'some_method()' of class A I should mock instance of class A (i.e. to mock 'self') to test 'some_method()'. Unit test is a high-end QA concept. Developers can get the best return on developer tests. They don't bother with aerospace-quality isolation between units. If a TDD test needs to pull in a bunch of modules to pass, that's generally a good thing, because they all get indirect testing. If they catch a bug, their local tests might not catch it, but the higher level tests still have a chance. (And if your product still needs unit tests, TDD will make them very easy for a formal QA team to add.) However, expensive setup is a design smell. That means if a test case requires too many lines of code for its Assemble phase (before its Activate and Assert phases), then maybe those lines of code support objects that are too coupled, and they need a better design. Throwing mocks at these objects, instead of decoupling them, will perfume the design smell, instead of curing it. construction encapsulation) And could you give an example. def test_frob(self): frob = Frob() frob.knob = Mock() frob.knob.value = Mock(return_value = 42) assert 42 == frob.method_using_knob() We need the mock because we can't control how Frob's constructor built its knob. So instead, give Frob the option to construct with a Knob: def test_frob(self): knob = Knob(42) frob = Frob(knob) assert frob.method_using_knob() Note that in production the Knob constructor never takes a Knob. Maybe we should upgrade the production code too (!), or maybe Knob's constructor should only create a knob if it didn't get passed one. Either technique is acceptable, because the resulting code decouples Frobs and Knobs just a little bit more. For me it's really hard to develop test first. Often I don't know what tests to write to replace hardcoded return values by objects that perform actual work. You have read too many books on TDD. C-: Alternate between writing lines of test and lines of code. Run the tests after the fewest possible edits, and always correctly predict if the tests will pass, or will fail, and with what diagnostic. (And configure your editor to run the stankin tests, no matter how hard it fights you!) The high-end tricks will get easier after you get the basic cycle down. -- Phlip http://c2.com/cgi/wiki?ZeekLand Hi Phlip! Thanks for your exhaustive answer. Actually, I'll investigate your example with 'frob'. From just reading the example it's not clear for me what I will benefit, using this approach. And I have already refused to write totally isolated tests, because it looks like a great waste of time. -- http://mail.python.org/mailman/listinfo/python-list
Which mock library do you prefer?
Hello! I am newbie mastering test driven development. I can't clarify myself which mock library to use. There are number of them and which one do you prefer? Two libraries that attracted my attention are: * minimock * dingus As for me the latest one, dingus, is the easiest (see this screencast: http://vimeo.com/3949077 ), but it has very few downloads from pypi, so it scares me a little. Minimock has wider usage and community, but I have some troubles using it. Maybe I am wrong, but with minimock you always have to keep track the order of imports in your test modules. Well, may be I just don't understand fully how minimock works. What are your suggestions? -- http://mail.python.org/mailman/listinfo/python-list
Re: Which mock library do you prefer?
On Feb 15, 6:57 pm, Phlip phlip2...@gmail.com wrote: Lacrima wrote: I am newbie mastering test driven development. I can't clarify myself which mock library to use. There are number of them and which one do you prefer? Two libraries that attracted my attention are: * minimock * dingus As for me the latest one, dingus, is the easiest (see this screencast:http://vimeo.com/3949077 ), but it has very few downloads from pypi, so it scares me a little. Minimock has wider usage and community, but I have some troubles using it. Maybe I am wrong, but with minimock you always have to keep track the order of imports in your test modules. Well, may be I just don't understand fully how minimock works. What are your suggestions? I have usedhttp://pypi.python.org/pypi/mock/0.6.0. It mocks, and it has a mode that works one method at a time, and another mode that mocks a method before its owning object gets constructed. However, TDD is not about mocking, and on greenfield code you should only mock to recover from some external problem, such as: - a random number generator - the system clock - anything over the wire - over a TCP/IP socket - hardware, such as your graphics or sound Never mock to avoid hitting the database. Some TDD verbiage advises never hit the database. That is a mind-game to force you to decouple your code. Your objects should always have the option (via construction encapsulation) to run as stubs, with some of their behaviors turned off. And if you TDD low-level code that hits a database, a mock would only tell the test what it wants to hear. And if you TDD high-level code that manages business rules, database records make perfectly good behavioral fixtures to support those rules. -- Phlip http://c2.com/cgi/wiki?ZeekLand Hi, Phlip! Thanks for your reply! Isn't what you are talking about integration tests? And unit tests should be fully isolated? So even for method 'some_method()' of class A I should mock instance of class A (i.e. to mock 'self') to test 'some_method()'. Please, could you explain in more detail your thoughts: Your objects should always have the option (via construction encapsulation) to run as stubs, with some of their behaviors turned off. And if you TDD low-level code that hits a database, a mock would only tell the test what it wants to hear. And if you TDD high-level code that manages business rules, database records make perfectly good behavioral fixtures to support those rules. And could you give an example. For me it's really hard to develop test first. Often I don't know what tests to write to replace hardcoded return values by objects that perform actual work. I have read several books on TDD and explored http://c2.com/cgi/wiki?TestDrivenDevelopment and related wikis, but often it seems I don't have enough understanding to write even simple application. And sorry for my English. with regards, Max. -- http://mail.python.org/mailman/listinfo/python-list
Re: what test runner should I use?
On Jan 19, 12:56 pm, Chris Withers ch...@simplistix.co.uk wrote: Hi All, I'm wondering what test runner I should use. Here's my list of requirements: - cross platform (I develop for and on Windows, Linux and Mac) - should not prevent tests from running with other test runners (so no plugins/layers/etc that only work with one specific test runner) - should work with zc.buildout (preferably without a specialist recipe!) So far I've tried the following with the resultant problems: zope.testing - requires a special recipe to be useful - now emits deprecation warnings from itself: https://mail.zope.org/pipermail/zope-dev/2009-December/038965.html - coverage support is baroque to put it politely twisted's trial - only has old-style script definition in setup.py, so doesn't work with buildout without hackery - drops _twisted_trial folders all over the place and doesn't clear them up nose - can't see to get it to run only my packages tests, rather than including the tests of packages my package depends on - seems to be focused towards files rather than modules (which makes it not play nicely with buildout) - seems to be difficult to provide options to at configuration time that can then be overridden on the command line I did also look at py.test's homepage but found it pretty scary. What other options do people recommend? Failing that, any ideas how to fix the problems above? cheers, Chris Nose should work pretty well with buildout. You need this in your buildout.cfg [buildout] parts = test [test] recipe = pbp.recipe.noserunner eggs = yourpackage1 yourpackage2 This will generate test script (bin/test), which will search and run tests only in packages, specified in eggs option. -- http://mail.python.org/mailman/listinfo/python-list
Re: Anybody use web2py?
On Dec 20, 1:35 am, mdipierro massimodipierr...@gmail.com wrote: Errata. I said The dal supports transactions where I meant the dal supports migrations. Of course it also supports transactions as well as distributed transactions. Sorry, if this is not related to this topic. Does web2py support distributed transactions with Google App Engine Datastore? -- http://mail.python.org/mailman/listinfo/python-list
TDD with nose or py.test
Hello! I am learning TDD with Python and there is not much information about this topic. Python is shipped with unittest module. That is fine, but I also discovered other libraries: nose and py.test. They promise to make life yet easier for a developer. But I still can't figure out, which combination I should use them in. Nose seems simpler than py.test, but py.test offers more features. And both py.test and nose say that they do not replace unittest module, but extend it. So as I understand my choice should be nose + unittest, or py.test + unittest. And now I'd like to hear about best practices in TDD in Python. Maybe not best practices, but basic approach. So which tests should I write with unittest, which with nose or py.test? How should I combine them? I am learning Python and I need your advice. Thanks in advance. Sorry if my English isn't very proper -- http://mail.python.org/mailman/listinfo/python-list
Sqlite3. Substitution of names in query.
Hello!
I use sqlite3 module for my sqlite database. I am trying to substitute
table name in sql query.
import sqlite3
con = sqlite3.connect('mydb')
cur = con.execute(select * from table where name='Joe')
That's ok
cur = con.execute(select * from table where name=?, ('Joe',))
That's ok too
cur = con.execute(select * from ? where name=?, ('table', 'Joe'))
Traceback (most recent call last):
File string, line 1, in fragment
sqlite3.OperationalError: near ?: syntax error
So what's wrong now?
Is it impossible to substitute table names, using DB API?
If so, what is a way to make table name substitutions? Are string
operations like
'select * from %s where...' % tablename
ok in this case?
Thanks in advance!
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Re: anydbm, gdbm, dbm
On Oct 27, 4:36 pm, Tim Chase python.l...@tim.thechases.com wrote: Lacrima wrote: I want to store some data, using anydbm module. According to docs the object returned by anydbm.open() supports most of the same functionality as dictionaries; keys and their corresponding values can be stored, retrieved, and deleted... I don't understand how I can make a table in DBM database, or a row in a table. Or all data must be stored just as key-value pairs? Yes, all data for the dbm variants is purely string-string mapping pairs. Similarly, dictionaries don't natively allow you to store columns in them...they are just key-value data-stores. Suppose my table consists of two columns: 'first name' and 'last name'. How can I make such table and write there first and last names for, say, two any persons? *dbm provides no columns unless you hack them such as db[key] = DELIMITER.join([lastname, firstname]) and then unhack them: lastname, firstname = db[key].split(DELIMITER, 1) As a variant of this, you might be able to use pickle/shelve to stash your multi-content object as a string-value. Alternatively, you could use something like db[%s_first % key] = firstname db[%s_last % key] = lastname assuming your keys didn't confound you. -tkc Hi! Thanks a lot! You've helped me very much! -- http://mail.python.org/mailman/listinfo/python-list
anydbm, gdbm, dbm
Hello! I want to store some data, using anydbm module. According to docs the object returned by anydbm.open() supports most of the same functionality as dictionaries; keys and their corresponding values can be stored, retrieved, and deleted... I don't understand how I can make a table in DBM database, or a row in a table. Or all data must be stored just as key-value pairs? Suppose my table consists of two columns: 'first name' and 'last name'. How can I make such table and write there first and last names for, say, two any persons? Thanks in advance... -- http://mail.python.org/mailman/listinfo/python-list
Design question.
Hello!
I am newbie in python and I have really simple question, but I need
your advice to know how to do best.
I need to store a number of dictionaries in certain place. I've
decided to store them in a separate module.
Like this:
dicts.py
---
dict1 = {}
dict2 = {}
dict3 = {}
Then, when I need any dictionary, I can access it:
import dicts
dicts.dict1
Is it a good practice? Or should I store them as class attributes or
anything else?
Thanks in advance.
With regards, Max
(sorry if my English isn't very proper)
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Re: Design question.
On Jul 20, 3:31 pm, Diez B. Roggisch de...@nospam.web.de wrote:
Lacrima wrote:
Hello!
I am newbie in python and I have really simple question, but I need
your advice to know how to do best.
I need to store a number of dictionaries in certain place. I've
decided to store them in a separate module.
Like this:
dicts.py
---
dict1 = {}
dict2 = {}
dict3 = {}
Then, when I need any dictionary, I can access it:
import dicts
dicts.dict1
Is it a good practice? Or should I store them as class attributes or
anything else?
It's perfectly fine to use dictionaries as module-level objects for storing
e.g. configuration-data.
OTOH it's also fine to do so as class-attributes. Choosing one over the
other has a lot to do with the actual problem you are working on.
Diez
Hi!
Thank you very much for your so soon reply!
With regards,
Max
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Re: Design question.
On Jul 20, 4:05 pm, Jean-Michel Pichavant jeanmic...@sequans.com
wrote:
Lacrima wrote:
Hello!
I am newbie in python and I have really simple question, but I need
your advice to know how to do best.
I need to store a number of dictionaries in certain place. I've
decided to store them in a separate module.
Like this:
dicts.py
---
dict1 = {}
dict2 = {}
dict3 = {}
Then, when I need any dictionary, I can access it:
import dicts
dicts.dict1
Is it a good practice? Or should I store them as class attributes or
anything else?
Thanks in advance.
With regards, Max
(sorry if my English isn't very proper)
Defining dict as a module attribute ic correct, but try to answer the
following question:
Is dict1 an attribute/property/declension of the object/entity defined
by the module dicts ?
If yes, then your design is correct.
An correct example:
fruits.py
apple = {}
banana = {}
An incorrect one:
fruit.py
---
apple={}
bicycle={}
Basically, the rule is very straightforward, set your dict as a module
attribute only if its one of its attribute (very nice paraphrase !)
Most of people (including me) tend to have a module, where they put
everything they have no idea about their location. This is a bad habit
and result from a uncontrolled/undocumented design. Usually documenting
objects in such modules is really painful.
Your proposal is fine from a python syntax point of view. I can't tell
of your design with names like (dicts.py and dict1,dict2) hoping you do
not intend to name them that way.
JM
Hi, Jean-Michel!
Thanks for your answer.
I am not going to have names like dicts.py and dict1,dict2. That was
just example. I wanted to know if it is correct to have dictionaries
on a module level. Now I know that this is correct. I want to collect
in one module a number of dictionaries, every of which describes a
separate web service. And my function in another module will import
required dictionary, depending on what web service should be used.
Thanks again for the help.
With regards,
Max.
(sorry if my English isn't very proper)
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Re: urllib with x509 certs
Hello! I've solved this problem, using pyCurl. Here is sample code. import pycurl import StringIO b = StringIO.StringIO() c = pycurl.Curl() url = 'https://example.com/' c.setopt(pycurl.URL, url) c.setopt(pycurl.WRITEFUNCTION, b.write) c.setopt(pycurl.CAINFO, 'cert.crt') c.setopt(pycurl.SSLKEY, 'mykey.key') c.setopt(pycurl.SSLCERT, 'mycert.cer') c.setopt(pycurl.SSLKEYPASSWD , 'pass phrase') c.perform() This also allow to specify CA, so your requests are more secure then with urllib. With regards, Max. -- http://mail.python.org/mailman/listinfo/python-list
Re: Emacs Python-mode. Newbie problem.
On Jul 8, 10:54 pm, Piet van Oostrum p...@cs.uu.nl wrote: Lacrima lacrima.ma...@gmail.com (L) wrote: L Hello! L I have just started using Emacs to write python scripts. L I installed python-mode.el L Then I just tried this code: L print 'hello world' L When I press C-c RET, new blank window is opened and emacs says: L (Shell command succeeded with no output) L So where is my 'hello world'? L When I do C-c C-c, it prints 'hello world' successfully. L Why in the first case I get no output? Can you check in the buffer where you have the python code what command C-c RET is bound to? With C-h k C-c RET Shell command succeeded with no output suggests that is has a different binding than the standard one in python-mode. Did you happen to name your file 'test' or 'test.py? C-c RET does an import and 'import test' imports a standard module test. -- Piet van Oostrum p...@cs.uu.nl URL:http://pietvanoostrum.com[PGP 8DAE142BE17999C4] Private email: p...@vanoostrum.org Hi, Piet! Thanks for your reply! My file name is 'trains.py'. When I do C-h k C-c RET, it shows me help from manual: C-c RET runs the command py-execute-import-or-reload which is an interactive Lisp function in `python-mode'... and so on. And still when I do C-c RET, I receive (Shell command succeeded with no output) Any more help would be really appreciated, because I am newbie with Emacs. With regards, Max -- http://mail.python.org/mailman/listinfo/python-list
Re: Emacs Python-mode. Newbie problem.
On Jul 9, 2:31 pm, Piet van Oostrum p...@cs.uu.nl wrote: Lacrima lacrima.ma...@gmail.com (L) wrote: L Thanks for your reply! L My file name is 'trains.py'. L When I do C-h k C-c RET, it shows me help from manual: C-c RET runs L the command py-execute-import-or-reload L which is an interactive Lisp function in `python-mode'... and so L on. L And still when I do C-c RET, I receive (Shell command succeeded with L no output) L Any more help would be really appreciated, because I am newbie with L Emacs. I tested it and I can get this message also. It happens when you have no Python shell running (*Python* buffer). The python code is then executed by calling the python shell command and catching the output. This output is displayed in the *Python Output* buffer. It happens also with C-c C-c and it will give the same message. There is a difference, however between C-c C-x and C-c RET: The latter will import your module, and most modules are written such that importing them doesn't print anything. If you add something like print test and the end of file, then test will appear in the *Python Output* buffer. If your file has the print hello world statement it should display in the *Python Output* buffer. I checked that. On the other hand, if you have a python shell running you must make sure (e.g. with the cd command) that its working directory is the directory where your python file is located, otherwise the import statement will not find your file. Unless it is somewhere in the python path. Also the *Python* buffer will not automatically pop up if it is not visible, in contrast with the *Python Output* buffer. -- Piet van Oostrum p...@cs.uu.nl URL:http://pietvanoostrum.com[PGP 8DAE142BE17999C4] Private email: p...@vanoostrum.org Thank you for really useful and detailed explanation. Now I can test my code using Emacs. But I think it works for me in a little bit different way. My file contains only the print 'hello world'. If I have no python shell running, then: a) C-c RET opens *Python Output* buffer without any output and with 'Shell command succeeded with no output' message at the bottom b) C-c C-c opens *Python Output* with appropriate 'hello world' message. Then I run python shell with C-c ! command. And: a) C-c RET opens *Python* buffer and prints 'hello world' in the python shell b) C-c C-c gives the same result. With regards, Max -- http://mail.python.org/mailman/listinfo/python-list
Re: Emacs Python-mode. Newbie problem.
On Jul 9, 8:42 pm, Piet van Oostrum p...@cs.uu.nl wrote: Lacrima lacrima.ma...@gmail.com (L) wrote: L Thank you for really useful and detailed explanation. Now I can test L my code usingEmacs. L But I think it works for me in a little bit different way. L My file contains only the print 'hello world'. L If I have no python shell running, then: L a) C-c RET opens *Python Output* buffer without any output and with L 'Shell command succeeded with no output' message at the bottom L b) C-c C-c opens *Python Output* with appropriate 'hello world' L message. L Then I run python shell with C-c ! command. And: L a) C-c RET opens *Python* buffer and prints 'hello world' in the L python shell L b) C-c C-c gives the same result. Which version of python-mode.el do you have? (Variable py-version) -- Piet van Oostrum p...@cs.uu.nl URL:http://pietvanoostrum.com[PGP 8DAE142BE17999C4] Private email: p...@vanoostrum.org py-version's value is 5.1.0 Also maybe the problem is because I use Emacs version 21.4.1. But I can't change it to 22, because I access Emacs via SSH on some shared hosting service. With regards, Max. -- http://mail.python.org/mailman/listinfo/python-list
Emacs Python-mode. Newbie problem.
Hello! I have just started using Emacs to write python scripts. I installed python-mode.el Then I just tried this code: print 'hello world' When I press C-c RET, new blank window is opened and emacs says: (Shell command succeeded with no output) So where is my 'hello world'? When I do C-c C-c, it prints 'hello world' successfully. Why in the first case I get no output? Thanks in advance! With regards, Max (sorry if my English isn't very proper) -- http://mail.python.org/mailman/listinfo/python-list
urllib with x509 certs
Hello! I am trying to use urllib to fetch some internet resources, using my client x509 certificate. I have divided my .p12 file into mykey.key and mycert.cer files. Then I use following approach: import urllib url = 'https://example.com' xml = '''request ... somexmlsomexml/somexml /request''' opener = urllib.URLopener(key_file = 'mykey.key', cert_file = 'mycert.cer') f = opener.open(url, xml) This works Ok! But every time I am asked to enter PEM pass phrase, which I specified during dividing my .p12 file. So my question... What should I do to make my code fetch any url automatically (without asking me every time to enter pass phrase)? As I understand there is impossible to specify pass phrase while constructing URLopener. So what should I do? With regards, Max (sorry if my English isn't very proper) -- http://mail.python.org/mailman/listinfo/python-list
Re: urllib with x509 certs
On Jul 4, 11:24 am, Chris Rebert c...@rebertia.com wrote:
On Sat, Jul 4, 2009 at 1:12 AM, Lacrimalacrima.ma...@gmail.com wrote:
Hello!
I am trying to use urllib to fetch some internet resources, using my
client x509 certificate.
I have divided my .p12 file into mykey.key and mycert.cer files.
Then I use following approach:
import urllib
url = 'https://example.com'
xml = '''request
... somexmlsomexml/somexml
/request'''
opener = urllib.URLopener(key_file = 'mykey.key', cert_file =
'mycert.cer')
f = opener.open(url, xml)
This works Ok! But every time I am asked to enter PEM pass phrase,
which I specified during dividing my .p12 file.
So my question... What should I do to make my code fetch any url
automatically (without asking me every time to enter pass phrase)?
As I understand there is impossible to specify pass phrase while
constructing URLopener.
So what should I do?
Subclass FancyURLopener
[http://docs.python.org/library/urllib.html#urllib.FancyURLopener],
overriding the prompt_user_passwd() method
[http://docs.python.org/library/urllib.html#urllib.FancyURLopener.prom...].
Then use an instance of your subclass instead of URLopener.
Cheers,
Chris
--http://blog.rebertia.com
Hi Chris,
Thanks for your quick reply.
According to docs the return value of prompt_user_passwd() method
should be a tuple (user, password), but there is no user when
authenticating with certificate. So how should I use this method? This
doesn't work:
import urllib
class MyOpener(urllib.FancyURLopener):
... def prompt_user_passwd(self, host, realm):
... return ('password')
...
With regards, Max
--
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Re: urllib with x509 certs
On Jul 4, 12:38 pm, Martin v. Löwis mar...@v.loewis.de wrote: This works Ok! But every time I am asked to enter PEM pass phrase, which I specified during dividing my .p12 file. So my question... What should I do to make my code fetch any url automatically (without asking me every time to enter pass phrase)? As I understand there is impossible to specify pass phrase while constructing URLopener. So what should I do? You can remove the passphrase on the private key, e.g. with the openssl rsa utility. Regards, Martin Hi Martin! Thanks for the reply. I want my key to be as secure as possible. So I will remove pass phrase if only there is no other possibility to go through authentication. With regards, Max -- http://mail.python.org/mailman/listinfo/python-list
Re: What text editor is everyone using for Python
I am new to python. And now I am using trial version of Wing IDE. But nobody mentioned it as a favourite editor. So should I buy it when trial is expired or there are better choices? -- http://mail.python.org/mailman/listinfo/python-list
Simple question about accessing instance properties.
Hello! I think I have a very simple question, but I can't understand how to access object properties in a way described below. For example I have an instance of any class: class Person: def __init__(self): self.name = 'John' self.email = 'j...@example.com' self.phone = '3453454' person = Person() Then I have a list of person's properties represented as strings: prop_list = ['name', 'email', 'phone'] And my question is how to access person's properties using prop_list? Do I have to somehow convert 'name', 'email', 'phone'? With regards, Max. -- http://mail.python.org/mailman/listinfo/python-list
Re: Simple question about accessing instance properties.
On May 21, 7:04 pm, MRAB goo...@mrabarnett.plus.com wrote: Lacrima wrote: Hello! I think I have a very simple question, but I can't understand how to access object properties in a way described below. For example I have an instance of any class: class Person: def __init__(self): self.name = 'John' self.email = 'j...@example.com' self.phone = '3453454' person = Person() Then I have a list of person's properties represented as strings: prop_list = ['name', 'email', 'phone'] And my question is how to access person's properties using prop_list? Do I have to somehow convert 'name', 'email', 'phone'? getattr(person, name) 'John' Hi! Thanks a lot!!! That's so simple! With regards, Max. -- http://mail.python.org/mailman/listinfo/python-list
Re: Checking for required arguments when instantiating class.
On May 6, 3:36 pm, Chris Rebert c...@rebertia.com wrote:
On Wed, May 6, 2009 at 5:24 AM, Piet van Oostrum p...@cs.uu.nl wrote:
Lacrima lacrima.ma...@gmail.com (L) wrote:
L Hello!
L For example I have two classes:
class First:
L def __init__(self, *args, **kwargs):
L pass
class Second:
L def __init__(self, somearg, *args, **kwargs):
L self.somearg = somearg
L How can I test that First class takes 1 required argument and Second
L class takes no required arguments?
L So that I could instantiate them in a for loop.
a = [First, Second]
for cls in a:
L instance = cls()
L Traceback (most recent call last):
L File pyshell#22, line 2, in module
L instance = cls()
L TypeError: __init__() takes at least 2 arguments (1 given)
L Of course, I can do like this:
for cls in a:
L try:
L instance = cls()
L except TypeError:
L instance = cls('hello')
print instance.somearg
L hello
L But what if I have to instantiate any class with 3 or 4 required
L arguments? How can I do it?
cls.__init__.im_func.__code__.co_argcount
This will include self, so it will be 1 in First and 2 in Second.
AFAICT, that would count non-required arguments too, which isn't
strictly what the OP requested.
However this is very dirty trickery and should not be recommended. It
may also change in future versions and other implementations of Python.
Very much agreed.
I think it would be cleaner to put a class attribute in the classes that
defines how they should be initialized (e.g. just the number of required
arguments or more specific information) or have a special factory method
for this use case.
Seconded. I'd recommend the latter personally, though it's impossible
to give a definitive answer without more context.
Cheers,
Chris
--http://blog.rebertia.com
Thanks for all of you!
I think I'll try to write a special method for this case and will
report you result.
-Max
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Checking for required arguments when instantiating class.
Hello!
For example I have two classes:
class First:
def __init__(self, *args, **kwargs):
pass
class Second:
def __init__(self, somearg, *args, **kwargs):
self.somearg = somearg
How can I test that First class takes 1 required argument and Second
class takes no required arguments?
So that I could instantiate them in a for loop.
a = [First, Second]
for cls in a:
instance = cls()
Traceback (most recent call last):
File pyshell#22, line 2, in module
instance = cls()
TypeError: __init__() takes at least 2 arguments (1 given)
Of course, I can do like this:
for cls in a:
try:
instance = cls()
except TypeError:
instance = cls('hello')
print instance.somearg
hello
But what if I have to instantiate any class with 3 or 4 required
arguments? How can I do it?
With regards,
Max
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Re: Checking for required arguments when instantiating class.
class First: def __init__(self, *args, **kwargs): pass class Second: def __init__(self, somearg, *args, **kwargs): self.somearg = somearg How can I test that First class takes 1 required argument and Second class takes no required arguments? Sorry, I have made a mistake. Of course, Second class takes 1 required argument, not First. -- http://mail.python.org/mailman/listinfo/python-list
Re: Restart generator when it is exhausted.
On Apr 28, 6:38 pm, J. Cliff Dyer j...@sdf.lonestar.org wrote:
On Tue, 2009-04-28 at 10:41 +, Duncan Booth wrote:
Lacrima lacrima.ma...@gmail.com wrote:
If it is not possible what are common techniques to use iterator or
generator objects that allow restarting when it is needed?
The usual thing if you want to use the generator's output more than once
would be to convert the generator to a list, then you can iterate over it
as often as you want.
a = ['a', 'b', 'c']
g = (i for i in a)
restartable = list(g)
If you want the output of the generator to potentially change each time you
iterate then you need to create a new generator.
More verbosely, but without putting your generator in , you can use the
iterator protocol to create a reusable iterable:
An iterable is a class with an __iter__ method that returns an iterator.
So for example:
class Iterator(object):
def __init__(self, filename):
self.f = open(filename)
def __iter__(self):
return self
def next(self):
line = self.f.readline()
if not line:
raise StopIteration
return line.strip()[:8]
is an iterator (which is also an iterable), which will grab each line of
a file, returning the first eight non-whitespace characters until the
file is used up. Then the iterator is exhausted, and will continue to
raise StopIteration each time it is called.
class Iterable(object):
def __init__(self, filename):
self.filename = filename
def __iter__(self):
return Iterator(self.filename)
This is a reusable iterable which returns a new instance of the Iterator
class above each time it is exhausted.
So given a file hello.txt:
Hello world
Hola mundo
Guten tag, weld.
The classes can be used as followed: iterator = Iterator('hello.txt')
for i in xrange(3):
print *** %d *** % i
for j in iterator:
print j
*** 0 ***
Hello wo
Hola mun
Guten ta
*** 1 ***
*** 2 *** iterable = Iterable('hello.txt')
for i in xrange(3):
print *** %d *** % i
for j in iterable:
print j
*** 0 ***
Hello wo
Hola mun
Guten ta
*** 1 ***
Hello wo
Hola mun
Guten ta
*** 2 ***
Hello wo
Hola mun
Guten ta
When Iterator hits a StopIteration, it passes out of the inner loop, and
when it comes back in, the inner loop calls iterator.__iter__(), and
gets the same exhausted iterator (which immediately breaks the inner
loop by raising StopIteration). In Iterable, when the loop calls
iterable.__iter__(), it gets a fresh iterator, so it can loop over the
file again.
The important thing is that when you call x.__iter__() (which you do
when entering a loop), you get a fresh iterator that won't just call
StopIteration right away.
Cheers,
Cliff
Thank you very much! You completely have enlightened me on all my
questions!
-Max
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Restart generator when it is exhausted.
Hello! I am quite new to Python and I have maybe simple (or maybe not) question. Is it possible to restart generator when it is exhausted? For example: a = ['a', 'b', 'c'] g = (i for i in a) g.next() 'a' g.next() 'b' g.next() 'c' g.next() Traceback (most recent call last): File pyshell#31, line 1, in module g.next() StopIteration What should I do to get the initial state of g? So if I do again g.next () I receive 'a'. If it is not possible what are common techniques to use iterator or generator objects that allow restarting when it is needed? With regards, Max (sorry if my English isn't very proper) -- http://mail.python.org/mailman/listinfo/python-list
Re: Restart generator when it is exhausted.
On Apr 28, 1:04 pm, Chris Rebert c...@rebertia.com wrote: On Tue, Apr 28, 2009 at 2:54 AM, Lacrima lacrima.ma...@gmail.com wrote: Hello! I am quite new to Python and I have maybe simple (or maybe not) question. Is it possible to restart generator when it is exhausted? No. You have to make a new instance of the generator. What should I do to get the initial state of g? So if I do again g.next () I receive 'a'. g = (i for i in a) #that is, make a fresh generator instance If it is not possible what are common techniques to use iterator or generator objects that allow restarting when it is needed? There's itertools.cycle() --http://docs.python.org/library/itertools.html#itertools.cycle Cheers, Chris --http://blog.rebertia.com Chris, thanks a lot for the help! -- http://mail.python.org/mailman/listinfo/python-list
