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Re: imported module no longer available

Jeff Dyke wrote:
>actually no, the only things in that fucntion were.
print globals().keys() - i see it here
print mymodulename - it fails here.

the `import mymodulename` statement is at the very top of the file.

plus the processing that was attempted after.
so how did that processing use the "mymodulename" name?
>in fact in the calling
method i was able to execute print mymodulename and it printed the
expected python output.
the calling method has nothing to do with what's considered to be a
local variable in the method being called, so that only means that the
name is indeed available in the global scope.
>So i went back to check that the name 'mymodulename' was not getting
overwritten by something else and the error went away. I've been
working on something else entirely for the past few hours and have
changed none of the code...and now it works. which is even more
troublesome then the error itself.
more likely, it indicates that you removed the line that caused Python
to treat that name as a local variable.
>Follow on question. If this name, mymodulename, was imported in some
other module.fucntion local to a function like
def anotherfunc():
import mymodulename

would that remove it from the globals() and save it to a locals() ? I
would assume the answer to be no.
even after reading the page I pointed you to?

import binds a name, so an import statement inside a function will cause
Python to treat that name as a local variable (unless you add a global
declaration to that function).

maybe a few examples will make this clearer; the following snippets are
complete programs:

snippet 1:

import module # adds module to the global namespace

def func():
module.func() # uses module from the global namespace

func() # no error here

snippet 2:

def func():
import module # adds module to the *local* namespace
module.func()

func() # no error here
module.func() # doesn't work; no module in global namespace

snippet 3:

def func():
global module # marks module as a global name
import module # adds module to the *global* namespace
module.func()

func() # no error here
module.func() # no error here; global module set by function

snippet 4:

import module # adds module to global namespace

def func():
import module # adds module to local namespace too
print module # prints local variable
module = None # sets local variable to None

func() # no error here
module.func() # no error here either; uses global namespace

snippet 5:

import module

def func():
print module # fails with an UnboundLocalError.
# lots of lines
import module # adds to local namespace; marks name as local
# some more code

func() # will fail at print statement

my guess is that the last snippet corresponds to your case.

</F>

Jul 21 '08 #1
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