module name versus function name resolution conflict.

[Dave Angel]

rocky wrote:
> Someone recently reported a problem in pydb where a function defined
> in his program was conflicting with a module name that pydb uses. I
> think I understand what's wrong, but I don't have any elegant
> solutions to the problem. Suggestions would be appreciated.
>
> In a nutshell, here's the problem:
>
> In file fns:
>
>   def foo(): print "foo"
>
> In file pdebug.py:
>
>   import fns, sys
>
>   def trace_dispatch(frame, event, arg):
>       fns.foo()
>       print frame, event, arg
>       return trace_dispatch
>
>   sys.settrace(trace_dispatch)
>   execfile('myprogram.py')
>
> Finally file myprogram.py:
>
>   def fns(): print "This is the *other* fns"
>
> When you run pdebug.py you get:
>
> $ python pdebug.py
> foo
> <frame object at 0xdd9030> call None
> foo
> <frame object at 0xdd9030> line None
> Traceback (most recent call last):
>   File "pdebug.py", line 7, in <module>
>     execfile('myprogram.py')
>   File "myprogram.py", line 1, in <module>
>     def fns(): print "This is the *other* fns"
>   File "pdebug.py", line 3, in trace_dispatch
>     fns.foo()
> AttributeError: 'function' object has no attribute 'foo'
>
>
> Basically inside the trace hook, local functions are visible and take
> precedence over (global) module names. I could move "import fns"
> inside trace_dispatch(), but I'd have to do that in all of the methods
> that module "fns" is used.  Also note that using the form:
>   from fns import foo
>
> would eliminate the conflict on "fns", but I'd still have potential
> conflicts on "foo". Using more obscure names (e.g. pydb_fns) would
> reduce the chance of a conflict but not eliminate it.
>
> Suggestions?
>
>
>   
Some context would be useful.  For example, you may be writing pdebug.py 
as a library to be used by other developers, and you want to minimize 
the likelihood that arbitrary code they write will conflict.  If you own 
all the code, I'd just say to rename one or the other.

My preference is also for using import of myprogram, as I've never 
needed execfile().  But if you need one of the features of execfile(), 
and really want myprogram in the same namespace, then you probably ought 
to obfuscate the other import.

Instead of   import fns,    try:
       import fns as _module_fns
And of course any references to the module will use the longer name.

The leading underscore is a clue that the name is not to be used outside 
of the module.  And the prefix 'module' helps to make it unlikely 
they'll make a data or function or class with that name.