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svn+ssh://pythondev@svn.python.org/python/trunk ........ r76886 | georg.brandl | 2009-12-19 18:43:33 +0100 (Sa, 19 Dez 2009) | 1 line #7493: review of Design FAQ by Florent Xicluna. ........
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@ -234,8 +234,10 @@ code breakage.
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.. XXX talk about protocols?
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Note that for string operations Python has moved from external functions (the
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``string`` module) to methods. However, ``len()`` is still a function.
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.. note::
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For string operations, Python has moved from external functions (the
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``string`` module) to methods. However, ``len()`` is still a function.
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Why is join() a string method instead of a list or tuple method?
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@ -306,14 +308,15 @@ expensive. In versions of Python prior to 2.0 it was common to use this idiom::
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This only made sense when you expected the dict to have the key almost all the
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time. If that wasn't the case, you coded it like this::
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if dict.has_key(key):
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if key in dict(key):
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value = dict[key]
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else:
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dict[key] = getvalue(key)
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value = dict[key]
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(In Python 2.0 and higher, you can code this as ``value = dict.setdefault(key,
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getvalue(key))``.)
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For this specific case, you could also use ``value = dict.setdefault(key,
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getvalue(key))``, but only if the ``getvalue()`` call is cheap enough because it
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is evaluated in all cases.
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Why isn't there a switch or case statement in Python?
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@ -750,7 +753,7 @@ requested again. This is called "memoizing", and can be implemented like this::
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# Callers will never provide a third parameter for this function.
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def expensive (arg1, arg2, _cache={}):
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if _cache.has_key((arg1, arg2)):
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if (arg1, arg2) in _cache:
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return _cache[(arg1, arg2)]
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# Calculate the value
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