[Python-Dev] Think a dead import finding script would be handy?

[Christian Heimes]

Brett Cannon wrote:
> After Christian mentioned how we could speed up interpreter start-up
> by removing some dead imports he found, I decided to write up a quick
> script that generates the AST for a source file and (very roughly)
> tries to find imports that are never used. People think it's worth
> tossing into Tools, even if it is kind of rough? Otherwise I might
> toss it into the sandbox or make a quick Google code project out of
> it.
> 
> Regardless, one interesting side-effect of the script is that beyond
> finding some extraneous imports in various places, it also found some
> holes in __all__. I have the script look for the definition of __all__
> and consider an import used if it is listed there.

Zope 3 has various tools for sorting imports or checking for unused 
imports. See http://svn.zope.org/Zope3/trunk/utilities/


Python 3.0 currently imports 25 modules on startup, Python 2.6 just 14:

./python -S -c "import sys; print(list(sorted(sys.modules)), 
len(sys.modules))"

['__main__', '_abcoll', '_codecs', '_fileio', '_thread', '_weakref', 
'_weakrefset', 'abc', 'builtins', 'codecs', 'copyreg', 'encodings', 
'encodings.aliases', 'encodings.latin_1', 'encodings.utf_8', 'errno', 
'genericpath', 'io', 'os', 'os.path', 'posix', 'posixpath', 'signal', 
'stat', 'sys', 'zipimport'] 26

_abcoll
   os.envirion uses _abcoll.MutableMapping

_weakref + _weakrefset
   imported for abc

abc
   imported for io.IOBase

copyreg
   imported by os to register some pickle handlers.
   Could be removed by placing the code into copyreg instead.

encodings.*
   imported early to avoid various bootstrapping issues (IIRC)

encodings.aliases:
   Could be removing by delaying the import until search_function()
   is called the first time

errno, genericpath, posix, posixpath, stat:
   import by os and os.path

stat:
   Could probably be replaced by a simple and faster C implementation
   in posixmodule.c to spare the import

signal:
   I'm not sure why the module is loaded at all.

I think we can get rid of copyreg and encodings.aliases easily.

Christian