Bugs item #1520864, was opened at 2006-07-11 23:21
Message generated for change (Comment added) made by gbrandl
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Category: Python Interpreter Core
Group: Python 2.5
>Status: Open
>Resolution: None
Priority: 9
Submitted By: Anthony Tuininga (atuining)
Assigned to: Neal Norwitz (nnorwitz)
Summary: unpack list of singleton tuples not unpacking
Initial Comment:
The following code works differently in Python 2.5 than
Python 2.4:
x = [(1,), (2,), (3,)]
for y, in x:
print y
In Python 2.4, this code produces the following:
1
2
3
In Python 2.5, this code produces the following:
(1,)
(2,)
(3,)
Interestingly enough the following code:
x = (1,)
y, = x
print y
produces the output
1
in both Python 2.4 and Python 2.5. I'm thinking this is
not intentional. :-)
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>Comment By: Georg Brandl (gbrandl)
Date: 2006-09-04 10:05
Message:
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You're right. Attached patch fixes this.
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Comment By: Sadruddin Rejeb (sadrejeb)
Date: 2006-09-04 09:08
Message:
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I have the impression that the bug has only been partially
solved, i.e. in 2.5c1, singleton tuples don't get unfoled in
list comprehensions.
Python 2.5c1 (r25c1:51305, Sep 4 2006, 10:15:09)
[GCC 4.1.1 20060525 (Red Hat 4.1.1-1)] on linux2
Type "help", "copyright", "credits" or "license" for more
information.
>>> l = [(1,), (2,)]
>>> print [x for x, in l]
[(1,), (2,)]
Same example in Python 2.4.3:
Python 2.4.3 (#1, Jul 25 2006, 11:53:03)
[GCC 4.1.1 20060525 (Red Hat 4.1.1-1)] on linux2
Type "help", "copyright", "credits" or "license" for more
information.
>>> l = [(1,), (2,)]
>>> print [x for x, in l]
[1, 2]
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Comment By: Neal Norwitz (nnorwitz)
Date: 2006-07-12 05:26
Message:
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Awww come on, can't we change the language just to make your
life difficult? ;-)
Thanks a lot for catching this!
Committed revision 50597.
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Comment By: Raymond Hettinger (rhettinger)
Date: 2006-07-12 02:38
Message:
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Ouch. This is bad. The disassembly shows that the compiler
isn't generating the unpack_sequence opcode.
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