when calling help() from the python interpreter on a function 
whose default argument is provided by another function 
( e.g. def foo(bar=baz() ) : .... ), help will call baz().

This can cause problems because baz() can alter statefull
data  like a file or database entry. 

This is both a bug in that it does this and in that
its undocumented 

To see this download the attached file and then : 
Python 2.6.2 (release26-maint, Apr 19 2009, 01:58:18) 
[GCC 4.3.3] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import bug
>>> help(bug)

at this point the file bug now has been written to disk. 
This is a problem

I've got to think there is a reason for this, but seeing as I cant 
come up with it , better safe than sorry.

Default args are evaluated when the module is imported, if the arg is a
function call, the function is called.
You can see how the file is created just after the import, you don't
even need to call help().

This behavior is documented here:
http://docs.python.org/tutorial/controlflow.html#default-argument-values

The doc doesn't mention explicitly function calls, that could be added.

Ezio is correct.  The file is already created while importing bug, not
due to the call to help().