python高阶函数filter_python高阶函数:filter(过滤器)

官网解释&＃xff1a;filter(function, iterable)

Construct a list from those elements of iterable for which function returns true. iterable may be either a sequence, a container which supports iteration, or an iterator. If iterable is a string or a tuple, the result also has that type; otherwise it is always a list. If function is None, the identity function is assumed, that is, all elements of iterable that are false are removed.

Note that filter(function, iterable) is equivalent to [item for item in iterable if function(item)] if function is not None and [item for itemin iterable if item] if function is None.

See itertools.ifilter() and itertools.ifilterfalse() for iterator versions of this function, including a variation that filters for elements where the function returns false.

str.strip([chars])

Return a copy of the string with the leading and trailing characters removed.

The chars argument is a string specifying the set of characters to be removed.

If omitted or None, the chars argument defaults to removing whitespace.

The chars argument is not a prefix or suffix; rather, all combinations of its

values are stripped:>>> &＃39;   spacious   &＃39;.strip()

&＃39;spacious&＃39;

>>> &＃39;www.example.com&＃39;.strip(&＃39;cmowz.&＃39;)

&＃39;example&＃39;

就是&＃xff0c;如果省略参数&＃xff0c;默认过滤空格。

#过滤list中的偶数

def get_odd(s):

return s % 2 &＃61;&＃61; 1;   #C语言绝对不能这么写

print "get odd:", filter(get_odd, [1, 2, 3, 4, 5, 6])

#过滤list中的空格

def not_empty(s):

return s and s.strip()   #s过滤了&＃39;None&＃39;元素&＃xff0c;s.strip()默认过滤空格

print "not_empty:", filter(not_empty, [&＃39;A&＃39;, &＃39; &＃39;, &＃39;B&＃39;, None, &＃39;C&＃39;, &＃39;  &＃39;])

补充&＃xff1a;

.strip(None/string)&＃xff1a;从头尾开始&＃xff0c;按对象字符串顺序删除

a.如果strip参数中没有对象头尾开始的字符&＃xff0c;则无法删除&＃xff0c;返回对象全字符str1 &＃61; &＃39;www.example.com&＃39;

print (str1.strip(&＃39;lcoz.&＃39;))

####strip参数中没有&＃39;w&＃39;/&＃39;m&＃39;&＃xff0c;两端删除受阻

b.如果strip参数中有对象的头尾开始字符&＃xff0c;则匹配删除参数中的字符&＃xff0c;返回未删除字符str1 &＃61; &＃39;www.example.com&＃39;

print (str1.strip(&＃39;lcwmeoza.&＃39;))

xamp   ####strip参数中没有&＃39;x&＃39;/&＃39;p&＃39;,两端删除受阻