New submission from samwyse <samw...@gmail.com>:
PEP 378 states;
format(n, "6,f").replace(",", "X").replace(".", ",").replace("X", ".")
This is complex and relatively slow. A better technique, which IMHO the
proposal should high-lighted, would be:
swap_commas_and_periods = bytes.maketrans(b',.', b'.,')
format(n, "6,f").translate(swap_commas_and_periods)
While performing the maketrans each time a string is formatted is slower than
the triple replace, calling it once and caching the result is faster. I have
tested with with the 3.1 interpreter; example timings follow.
>>> Timer("""
'1,234,567.89'.replace(',', 'X').replace('.', ',').replace('X', '.')
""").timeit()
3.0645400462908015
>>> Timer("""
'1,234,567.89'.translate(swap_commas_and_periods)
""", """
swap_commas_and_periods = bytes.maketrans(b',.', b'.,')
""").timeit()
2.276630409730846
>>> Timer("""
'1,234,567.89'.translate(bytes.maketrans(b',.', b'.,'))
""").timeit()
3.760715677551161
----------
assignee: d...@python
components: Documentation
messages: 119427
nosy: d...@python, samwyse
priority: normal
severity: normal
status: open
title: PEP 378 uses replace where translate may work better
type: behavior
versions: Python 2.7, Python 3.1
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue10178>
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