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authorGeorg Brandl <georg@python.org>2009-12-19 17:46:40 (GMT)
committerGeorg Brandl <georg@python.org>2009-12-19 17:46:40 (GMT)
commitbfe95ac098ba37243df068a473c090e2935f26ff (patch)
treea777e6c4bb71e95a4d1344b5617c6abae263fb94 /Doc
parent4d345ce1c9115cd4e8a731c19576eae27b341bb4 (diff)
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Recorded merge of revisions 76886 via svnmerge from
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. ........
Diffstat (limited to 'Doc')
-rw-r--r--Doc/faq/design.rst15
1 files changed, 9 insertions, 6 deletions
diff --git a/Doc/faq/design.rst b/Doc/faq/design.rst
index c5af2fd..9ec6cad 100644
--- a/Doc/faq/design.rst
+++ b/Doc/faq/design.rst
@@ -234,8 +234,10 @@ code breakage.
.. XXX talk about protocols?
-Note that for string operations Python has moved from external functions (the
-``string`` module) to methods. However, ``len()`` is still a function.
+.. note::
+
+ For string operations, Python has moved from external functions (the
+ ``string`` module) to methods. However, ``len()`` is still a function.
Why is join() a string method instead of a list or tuple method?
@@ -306,14 +308,15 @@ expensive. In versions of Python prior to 2.0 it was common to use this idiom::
This only made sense when you expected the dict to have the key almost all the
time. If that wasn't the case, you coded it like this::
- if dict.has_key(key):
+ if key in dict(key):
value = dict[key]
else:
dict[key] = getvalue(key)
value = dict[key]
-(In Python 2.0 and higher, you can code this as ``value = dict.setdefault(key,
-getvalue(key))``.)
+For this specific case, you could also use ``value = dict.setdefault(key,
+getvalue(key))``, but only if the ``getvalue()`` call is cheap enough because it
+is evaluated in all cases.
Why isn't there a switch or case statement in Python?
@@ -750,7 +753,7 @@ requested again. This is called "memoizing", and can be implemented like this::
# Callers will never provide a third parameter for this function.
def expensive (arg1, arg2, _cache={}):
- if _cache.has_key((arg1, arg2)):
+ if (arg1, arg2) in _cache:
return _cache[(arg1, arg2)]
# Calculate the value