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Issue #12666: Added section about map changes.

This commit is contained in:
Jason R. Coombs 2011-12-03 08:24:21 -05:00
parent df9a5f5ecf
commit a90e364ea5
1 changed files with 12 additions and 0 deletions
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Doc/howto/pyporting.rst
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@ -505,6 +505,18 @@ Otherwise it might very well be worth your time and effort to port your tests
to :mod:`unittest`. to :mod:`unittest`.
Update `map` for imbalanced input sequences
'''''''''''''''''''''''''''''''''''''''''''
With Python 2, `map` would pad input sequences of unequal length with
`None` values, returning a sequence as long as the longest input sequence.
With Python 3, if the input sequences to `map` are of unequal length, `map`
will stop at the termination of the shortest of the sequences. For full
compatibility with `map` from Python 2.x, also wrap the sequences in
:func:`itertools.zip_longest`, e.g. ``map(func, *sequences)`` becomes
``list(map(func, itertools.zip_longest(*sequences)))``.
Eliminate ``-3`` Warnings Eliminate ``-3`` Warnings
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