Calling a function in __main__ from a module?
mshapiro at sunlitsurf.com
Fri Dec 19 01:40:09 CET 2003
On 18 Dec 2003 19:21:14 +0000, John J. Lee <jjl at pobox.com> wrote:
> Marc Shapiro <mshapiro at sunlitsurf.com> writes:
>> Traceback (most recent call last):
>> File "./hp", line 62, in ?
>> File "/usr/lib/python2.3/curses/wrapper.py", line 44, in wrapper
>> res = func(stdscr, *rest)
>> File "./hp", line 58, in main
>> File "/home/mns/menu.py", line 258, in mainloop
>> exec cmd + "('" + name + "')"
>> File "<string>", line 1, in ?
>> NameError: name 'NOP' is not defined
>> 'NOP' is the name of the function that I am trying to call. It does
>> not exist in the menu module, but is in the calling (hp) module. I
>> can't qualify the name (i.e. __main__.NOP() ) since __main__ can not
>> be used for qualification, only called module names can be used that
>> How do I get the module to call functions in a parent module. Tkinter
>> would set up a callback function and bind it to an event. Can
>> something similar be done for a console program using curses?
> Stop thinking about 'the parent module'. The question of *which*
> module wants to get at a particular function is irrelevant. Think
> like this instead: you have a bunch of modules, which any piece of
> Python code is free to import stuff from, and you have a main program
> which can be a module or not as you choose (if it's on sys.path, it's
> a module, if it's not, it ain't; if it *is* a module, you'll also have
> an if __name__ == "__main__" to prevent the program startup code
> getting executed at times other than program startup).
> So, you want to get at your NOP function. Two obvious choices:
> 1. import it
> 2. pass it as a function argument
> If 1, just make sure the file you want to import it from is on
> sys.path (or in a package that's on sys.path; a package is a directory
> on sys.path that contains an __init__.py file). You can always just
> grab your program startup code (say, main()), and stick it in a tiny
> executable file somewhere convenient like ~/bin, and move any other
> code that was originally in the same file into a module.
> BTW, I have never yet used exec or eval, and I've written a fair
> amount (tens of thousands of lines) of Python code. Whatever you
> think you need them for, you probably don't.
I was just about to post back that I had solved the problem. As it turns
out, I used method 2. I passed a function argument in place of a string
with the function name. Thanks to Python being an untyped language this
required only a few minor changes in the module and it is now working as
expected. My planned next step was, indeed, to see if I could rewrite so
as to avoid using 'exec'. It can certainly be confusing to determine what
is being evaluated by which sections of code and at what time. I am sure
that when it comes to maintaining this at a later date that it will be a
much easier task if I can get rid of the 'exec' lines.
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