在3.3里,如果直接使用map(), filter(),reduce(), 会出现
>>> def f(x): return x % 2 != 0 and x % 3 != 0
>>> filter(f, range(2, 25))
<</span>filter object at 0x0000000002C14908>
>>> def cube(x): return x*x*x
>>> map(cube, range(1, 11))
<</span>map object at 0x0000000002C82B70>
>>> def add(x,y): return x+y
>>> reduce(add, range(1, 11))
Traceback (most recent call last):
File "", line 1, in <</span>module>
reduce(add, range(1, 11))
NameError: name 'reduce' is not defined
这种情况是因为在3.3里面,map(),filter()这些的返回值已经不再是list,而是iterators, 所以想要使用,只用将iterator 转换成list 即可, 比如 list(map())
而reduce已经取消了,如想使用,可以用fuctools.reduce来调用。但是要先导入fuctools, 即输入:import fuctools
e.g1
>>> sentence = 'It is raining cats and dogs'
>>> words = sentence.split() >>> print words
['It', 'is', 'raining', 'cats', 'and', 'dogs']
>>> >>> lengths = map(lambda word: len(word), words) >>> print(list(lengths))
[2, 2, 7, 4, 3, 4] e.g2
>>> import functools
>>> def add(x,y): return x+y
...
>>> functools.reduce(add, range(1, 11))
55
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