[ python-Bugs-1328959 ] Empty Generator doesn't evaluate as False

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Bugs item #1328959, was opened at 2005-10-17 13:26
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Category: None
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Christian Höltje (docwhat)
Assigned to: Nobody/Anonymous (nobody)
Summary: Empty Generator doesn't evaluate as False

Initial Comment:
The following code doesn't work correctly if the
function "generator()" doesn't have any values.

if generator():
  print "This should only happen when the generator
runs yield"
  print " but it is always true, even if the generator
is empty"
else:
  print "this is the expected path when the generator
is empty"

The workaround is:

try:
  generator().next()
  print "this is the true case"
except StopIteration:
  print "this is the false case"

This means that generators are not transparent and they
don't behave as expected (like a list or tuple).

I've been bitten by this enough that I am unhappy. :-(

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You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1328959&group_id=5470