| msg18697 - (view) |
Author: Tim Delaney (tcdelaney) |
Date: 2003-10-20 23:41 |
| According to the email thread starting: http://mail.python.org/pipermail/python-dev/2003- October/039081.html the control variable name in a list comprehension should not be leaked and any use of such a leaked name is deprecated. |
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| msg18698 - (view) |
Author: Terry J. Reedy (terry.reedy) *  |
Date: 2003-10-21 00:04 |
| Logged In: YES user_id=593130 Ref Man 5.2.4 List displays: suggested addition at end. Using leaked 'for <exp_list>' control variables outside the list display is deprecated and will not work when the bug is fixed. |
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| msg18699 - (view) |
Author: Skip Montanaro (skip.montanaro) *  |
Date: 2003-10-21 13:52 |
| Logged In: YES user_id=44345 A good point raised by Michael Hudson is that foo = [x for x in R] print x will fail if R is empty (and x wasn't previously defined). All the more reason to deprecate its usage and suppress the leaking variable. |
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| msg18700 - (view) |
Author: Sjoerd Mullender (sjoerd) * |
Date: 2003-10-21 14:26 |
| Logged In: YES user_id=43607 Actually, this is not different from $ python Python 2.4a0 (#2, Oct 14 2003, 11:28:48) [GCC 3.2.2 20030222 (Red Hat Linux 3.2.2-5)] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> for x in []: ... pass ... >>> print x Traceback (most recent call last): File "", line 1, in ? NameError: name 'x' is not defined >>> where x is also undefined after iteraring through an empty list. |
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| msg18701 - (view) |
Author: Terry J. Reedy (terry.reedy) * |
Date: 2003-10-21 18:19 |
| Logged In: YES user_id=593130 The tutorial will also need revision of deletion: 5.1.4 List Comprehensions has this: To make list comprehensions match the behavior of for loops, assignments to the loop variable remain visible outside of the comprehension: >>> x = 100 # this gets overwritten >>> [x**3 for x in range(5)] [0, 1, 8, 27, 64] >>> x # the final value for range(5) 4 |
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| msg18702 - (view) |
Author: Alex Martelli (aleax) * |
Date: 2003-11-02 17:28 |
| Logged In: YES user_id=60314 I notice that the tutorial currently in CVS seems to have been already fixed (by exciding the paragraph tjreedy quoted). To fix the reference manual, I propose the enclosed patch. |
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| msg18703 - (view) |
Author: A.M. Kuchling (akuchling) * |
Date: 2004-08-07 19:16 |
| Logged In: YES user_id=11375 I've applied Alex's suggested patch. Thanks, everyone. |
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