Python内置函数：

官方帮助文档：

https://docs.python.org/2.7/

返回数字的绝对值.def fun(x):if x < 0:return -xreturn xprint fun(10)常用函数：abs()>>> abs(-100)100取列表最大值和最小值max()>>> max('1235',123)'1235'min()>>> min('asdfq3w45')'3'len()>>> len('abcdf')5>>> len([1,3,4,5])4>>> len((1,3,4,5))4>>> len({1:3,2:5})2divmod()>>> help(divmod)Help on built-in function divmod in module __builtin__:divmod(...)divmod(x, y) -> (quotient, remainder)Return the tuple (x//y, x%y). Invariant: div*y + mod == x. >>> divmod(5,2)(2, 1)pow()pow(...)pow(x, y[, z]) -> numberWith two arguments, equivalent to x**y. With three arguments,equivalent to (x**y) % z, but may be more efficient (e.g. for longs).>>> pow(2,3)8>>> pow(2,3,3)2round()round(...)round(number[, ndigits]) -> floating point numberRound a number to a given precision in decimal digits (default 0 digits).This always returns a floating point number. Precision may be negative.>>> round(12.2)12.0>>> round(12.23)12.0>>> round(12.233,2)12.23callable()是否是可调用对象>>> a = 123>>> callable(a)False>>> def a():... pass...>>> callable(a)True>>> class A(object):... pass...>>> callable(A)Truetype()判断类型>>> type(a)<type 'function'>isinstance()判断类型,>>> l =[1,2,3]>>> isinstance(l,list)True>>> isinstance(l,str)False>>> isinstance(l,(list,str))True判断是不是一个类>>> A<class 'A'>>>> a = A()>>> a<A object at 0x0379BE70>>>> isinstance(a,A)Truecmp()>>> cmp(1,2)-1>>> cmp(1,0)1>>> cmp(1,1)0>>> cmp('a','ab')-1>>> cmp('a','a')0>>> cmp('helloa','hello')1range()>>> a = range(10)>>> axrange()效率更高，不用时候不在内存中产生值[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>>> b = xrange(10)>>> bxrange(10)>>> for i in b:print i...0123456789int()>>> int(123.33)123long()>>> long(200)200Lfloat()>>> float('123')123.0>>> float('123.0022')123.0022>>> float(123.0034)123.0034>>> float(123)123.0complex()转换成复数>>> complex(123)(123+0j)>>> complex(3.1415926)(3.1415926+0j)str()>>> str('123')'123'list()>>> list('123')['1', '2', '3']tuple()>>> tuple('123')('1', '2', '3')hex()变为16进制>>> hex(10)'0xa'>>> hex(10L)'0xaL'>>> int(0xaL)10eval（）把字符串当成有效表达式求值。>>> eval('0xaL')10L>>> eval("[1,23,'a']")[1, 23, 'a']oct()10进制转成8进制>>> oct(10)'012'>>> oct(8)'010'chr()查ASSIC码对应值:>>> chr(97)'a'>>> chr(65)'A'ord()>>> ord('A')65字符串处理的函数：str.capitalize()首字母变大写：capitalize(...)S.capitalize() -> stringReturn a copy of the string S with only its first charactercapitalized.>>> s'hello'>>> s.capitalize()'Hello'str.replace()replace(...)S.replace(old, new[, count]) -> stringReturn a copy of string S with all occurrences of substringold replaced by new. If the optional argument count isgiven, only the first count occurrences are replaced.>>> s = 'hello,h'>>> s.replace('h','H')'Hello,H'split()split(...)S.split([sep [,maxsplit]]) -> list of stringsReturn a list of the words in the string S, using sep as thedelimiter string. If maxsplit is given, at most maxsplitsplits are done. If sep is not specified or is None, anywhitespace string is a separator and empty strings are removedfrom the result.>>> s = 'hello a\tb\nc'>>> s'hello a\tb\nc'>>> s.split()['hello', 'a', 'b', 'c']>> s'hello a\tb\nc'>>> s.split(' ')['hello', 'a\tb\nc']>>> s.split('\t')['hello a', 'b\nc']>>> ip = '192.168.1.1'>>> ip.split('.')['192', '168', '1', '1']>>> ip.split('.',1)['192', '168.1.1']>>> ip.split('.',2)['192', '168', '1.1']join()>>> range(10)[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>>> ''.join(str(i) for i in range(10))'0123456789'>>> int(''.join(str(i) for i in range(10)))123456789string:import stringstring.lower>>> string.lower('Kfdfa')'kfdfa'string.upper>>> string.upper('Kfdfa')'KFDFA'string.capitalize()>>> string.capitalize('adfafgh')'Adfafgh' string.replace()string.replace('afkgha','a','A')'AfkghA'序列处理函数：len()max()min()filter()filter(...)filter(function or None, sequence) -> list, tuple, or stringReturn those items of sequence for which function(item) is true. Iffunction is None, return the items that are true. If sequence is a tupleor string, return the same type, else return a list.>>> filter(None,range(10))[1, 2, 3, 4, 5, 6, 7, 8, 9]>>> def f(x):... if x % 2 == 0:... return True...>>> filter(f,range(10))[0, 2, 4, 6, 8]>>> filter(lambda x: x%2==0,range(10))[0, 2, 4, 6, 8]zip()zip(...)zip(seq1 [, seq2 [...]]) -> [(seq1[0], seq2[0] ...), (...)]Return a list of tuples, where each tuple contains the i-th elementfrom each of the argument sequences. The returned list is truncatedin length to the length of the shortest argument sequence.>>> a1 = [1,3,4]>>> a2 = ['a','b','c']>>> zip(a1,a2)[(1, 'a'), (3, 'b'), (4, 'c')]>>> dict(zip(a1,a2)){1: 'a', 3: 'b', 4: 'c'}>>> dict(zip(a2,a1)){'a': 1, 'c': 4, 'b': 3}>>> a3 = ['x','y','z']>>> zip(a1,a2,a3)[(1, 'a', 'x'), (3, 'b', 'y'), (4, 'c', 'z')]>>> zip(a1,a3)[(1, 'x'), (3, 'y'), (4, 'z')]>>> a3 = ['x','y']>>> zip(a1,a3)[(1, 'x'), (3, 'y')]>>> zip(a1,a2,a3)[(1, 'a', 'x'), (3, 'b', 'y')]map()map(...)map(function, sequence[, sequence, ...]) -> listReturn a list of the results of applying the function to the items ofthe argument sequence(s). If more than one sequence is given, thefunction is called with an argument list consisting of the correspondingitem of each sequence, substituting None for missing values when not allsequences have the same length. If the function is None, return a list ofthe items of the sequence (or a list of tuples if more than one sequence).参数有几个，函数里的参数也应该对应有几个>>> map(None,a1,a2,a3)[(1, 'a', 'x'), (3, 'b', 'y'), (4, 'c', None)]>>> def f(x):... return x**2...>>> map(f,a1)[1, 9, 16]>>> a1[1, 3, 4]>>> a1[1, 3, 4]>>> a2[2, 5, 6]>>> def f(x,y):... return x*y...>>> map(f,a1,a2)[2, 15, 24]>>> map(lambda x,y: x*y ,range(1,10),range(1,10))[1, 4, 9, 16, 25, 36, 49, 64, 81]reduce()reduce(...)reduce(function, sequence[, initial]) -> valueApply 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 itemsof the sequence in the calculation, and serves as a default when thesequence is empty.>>> def f(x,y):... return x + y...>>> reduce(f,range(1,101))5050列表表达式：[i*2 for i in range(10)]>>> [i*2 for i in range(10)][0, 2, 4, 6, 8, 10, 12, 14, 16, 18]>>> [i*2+10 for i in range(10)][10, 12, 14, 16, 18, 20, 22, 24, 26, 28][i*2+10 for i in range(10) if i%3 == 0]>>> [i*2+10 for i in range(10) if i%3 == 0][10, 16, 22, 28]