Q's on my first python script
socyl at 987jk.com.invalid
Sun May 10 22:43:21 CEST 2009
In <0216ec41$0$20647$c3e8da3 at news.astraweb.com> Steven D'Aprano <steve at REMOVE-THIS-cybersource.com.au> writes:
>On Sun, 10 May 2009 12:52:21 +0000, kj wrote:
>> 1. The name of the BadArgument exception class defined in the script
>> does not seem to me sufficiently specific. If one were to import the
>> script in order to reuse its wkday_abbrev function, I'd like this
>> exception's name to be more unequivocally tied to this script. What
>> I'm looking for is something like a "namespace" for this script.
>> What's the pythonic way to construct a namespace?
>You already have one. The module you have created is a namespace. If your
>script is called "myscript.py", then to use it elsewhere you would do:
>> 2. In some python modules I've seen the idiom
>> if __name__ == "__main__":
>> # run some tests here
>> I'd like to set up tests for this script, mostly to ensure that it
>> handles the error cases properly, but I'm alread using the idiom
>> above to actually run the script under normal operation. What's the
>> typical python idiom for running tests on a *script* (as opposed to a
>> module that is normally not supposed to be run directly)?
>I sometimes give my scripts an option -t or --self-test, and then run
>tests if that option is passed on the command line.
>Alternatively, put your tests in another module, say, myscript_tests.py,
>and then just run that when you want to test myscript.
>> 3. Still on the subject of testing, how does one capture in a
>> variable the output that would normally have gone to stdout or
>Normally you would write the function to *return* the result, rather than
>*print* the result. If all output goes through the function return
>mechanism, then it's easy to capture: x = func().
>However, for cases where the function does print directly, you can
>redefine stdout and strerr to be any file-like object, so you can do
>something like this:
>save_stdout, save_stderr = sys.stdout, sys.stderr
>c1 = cStringIO.StringIO()
>c2 = cStringIO.StringIO()
> sys.stdout = c1
> sys.stderr = c2
> result = func(*args, **kwargs) # normally prints some stuff
> # restore standard files
> sys.stdout = save_stdout
> sys.stderr = save_stderr
>captured_from_stdout = c1.getvalue()
>captured_from_stderr = c2.getvalue()
>> 4. What's the python way to emit warnings? (The script below should
>> warn the user that arguments after the first one are ignored.)
>warnings.warn("The end of the world is coming!")
>> 5. The variable wd is meant to be "global" to the script. In other
>> languages I've programmed in I've seen some typographic convention
>> used for the name of such variables (e.g. all caps) to signal this
>> widened scope. Does python have such a convention?
>As a general rule, it's best to avoid globals variables as much as
>One convention I occasionally use is to prefix global variables with a
>lowercase g. And then ruthlessly refactor my code until any variable
>starting with a lowercase g is removed :)
Thanks! That was very helpful!
NOTE: In my address everything before the first period is backwards;
and the last period, and everything after it, should be discarded.
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