本节主要内容：
python内建函数之string与list的用法
string处理
list处理
1. str.capitalize() 首字母大写
capitalize(...)
S.capitalize() -> string
Return a copy of the string S with only its first character
capitalized.
>>>
>>> "abc".capitalize()
'Abc'
2. str.replace() 替换
replace(...)
S.replace(old, new[, count]) -> string
Return a copy of string S with all occurrences of substring
old replaced by new. If the optional argument count is
given, only the first count occurrences are replaced.
>>>
>>> "1999-09-19".replace("-", "/")
'1999/09/19'
>>> "1999-09-19".replace("-", "/", 1)
'1999/09-19'
3. str.split() 分割,切割
split(...)
S.split([sep [,maxsplit]]) -> list of strings
Return a list of the words in the string S, using sep as the
delimiter string. If maxsplit is given, at most maxsplit
splits are done. If sep is not specified or is None, any
whitespace string is a separator and empty strings are removed
from the result.
>>>
>>> "1999-09-19".split()
['1999-09-19']
>>> "1999-09-19".split("-")
['1999', '09', '19']
>>> "1999-09-19".split("-",1)
['1999', '09-19']
4. string.replace()
>>> import string
>>> help(string.replace)
Help on function replace in module string:
replace(s, old, new, maxreplace=-1)
replace (str, old, new[, maxreplace]) -> string
Return a copy of string str with all occurrences of substring
old replaced by new. If the optional argument maxreplace is
given, only the first maxreplace occurrences are replaced.
>>>
>>> string.replace("192.168.10.110", ".", "-")
'192-168-10-110'
5. filter(), 保留符合条件的元素
filter(...)
filter(function or None, sequence) -> list, tuple, or string
Return those items of sequence for which function(item) is true. If
function is None, return the items that are true. If sequence is a tuple
or string, return the same type, else return a list.
>>>
>>> filter( lambda x: x > "1", "0123" )
'23'
>>> filter( lambda x: x > 1, ( 0, 1, 2, 3 ) )
(2, 3)
>>> filter( lambda x: x > 1, range(-1, 4) )
[2, 3]
6. zip() 合并两个sequence
zip(...)
zip(seq1 [, seq2 [...]]) -> [(seq1[0], seq2[0] ...), (...)]
Return a list of tuples, where each tuple contains the i-th element
from each of the argument sequences. The returned list is truncated
in length to the length of the shortest argument sequence.
>>>
>>> zip( (1, 2), (1, 2, 3) )
[(1, 1), (2, 2)]
>>> zip( [1, 2, 3], [1, 2] )
[(1, 1), (2, 2)]
7. map() 将sequence转成list,
map(...)
map(function, sequence[, sequence, ...]) -> list
Return a list of the results of applying the function to the items of
the argument sequence(s). If more than one sequence is given, the
function is called with an argument list consisting of the corresponding
item of each sequence, substituting None for missing values when not all
sequences have the same length. If the function is None, return a list of
the items of the sequence (or a list of tuples if more than one sequence).
>>>
>>> map(None, [1,2,3], ['a', 'b'])
[(1, 'a'), (2, 'b'), (3, None)]
>>> map(lambda x : x, "123")
['1', '2', '3']
>>> map(lambda x,y : x+y, [1,2,3], [10,20,30])
[11, 22, 33]
8. zip() 与 map() 的异同
-当map中function为None时, map()的功能与zip()一致, 都是并行遍历.
不同的是map()以最长的序列为准, 不足的补None,而zip()以最短的为准.
-当map中function不为None时, 会依次从各个sequence中取相同index的值做运算.
9. reduce() 依次取出每个item
reduce(...)
reduce(function, sequence[, initial]) -> value
Apply a function of two arguments cumulatively to the items of a sequence,
from left to right, so as to reduce the sequence to a single value.
For example, reduce(lambda x, y: x+y, [1, 2, 3, 4, 5]) calculates
((((1+2)+3)+4)+5). If initial is present, it is placed before the items
of the sequence in the calculation, and serves as a default when the
sequence is empty.
>>># 4!
>>> reduce(lambda x,y : x*y, [1, 2, 3, 4])
24
>>># 1+2+...+99+100
>>> reduce(lambda x,y : x+y, xrange(1, 101))
5050