[Python-ideas] [Python-Dev] If you shadow a module in the standard library that IDLE depends on, bad things happen

[Erik]

On 01/11/15 09:49, Laura Creighton wrote:
> Adding warnings to IDLE when you save a file is a fine idea, and will
> help IDLE users avoid pain.  I want to help _everybody_ with a change
> to Python, so that it issues a warning when you shadow something in
> the standard library.

I think that a solution to this could be something along the lines of 
having a command line switch (let's say '-w') or other way of enabling a 
"shadow module checking" mechanism.

When an exception is thrown that is caught by the default handler and 
output to stderr, an additional line of output could be appended:

"Note: This problem could be caused by a module that shadows a standard 
library or third party module. Run Python with the '-w' switch for more 
detail."

I'm not sure if this would be suitable for _all_ exceptions or only 
those from certain points in the exception hierarchy.

When the '-w' switch is enabled, the default exception handler would 
instead enumerate all active modules and, for any which has another 
module with the same name further down the search path than the one that 
is loaded, would output some sort of diagnostic message (i.e., a list of 
which loaded modules are shadowing _something_else_ that would have been 
loaded otherwise) - similar to your example below:

> Something like:
> Warning: local file /u/lac/junk/string.py shadows module named string in the
> Standard Library

This would prevent "power users" from always having to see a potentially 
large diagnostic after each uncaught exception, but generally remind 
everyone that such a thing is possible and "here's the easy way to check 
for it".

A bit like Valgrind's memcheck tool's "--leak-check=full" option - when 
run without it, if there are leaks then memcheck reminds the user that 
that's the way to start digging down into what might be causing them.

E.