Exceptions and modules / namespaces question

[Samuele Pedroni]

The problem is that "import module1" in
module2 is re-executing your main script
a second time and so creating new
definitions.

The main script, as the "if __name__ ==
 '__main__' " idiom hints, appear as loaded (in the module
cache sys.modules)
under such a name, so "import module1"
triggers the loading of module1.py
as distinct (new) module from the main script.

Consider:

#mod.py:
class C: pass

if __name__ == '__main__':
  import mod
  import sys
  print "module __main__: ",sys.modules['__main__']
  print "module mod:", mod
  print  "are the same?",{0: 'n',1: 'y'}[sys.modules['__main__'] is mod.C]
  print "class C in main script:",C
  print "class C from mod:",mod.C
  print  "are the same?",{0: 'n',1: 'y'}[C is mod.C]

Output:
$python mod.py
module __main__:  <module '__main__' (built-in)>
module mod: <module 'mod' from 'mod.pyc'>
are the same? n
class C in main script: __main__.C
class C from mod: mod.C
are the same? n

regards.