4.8Python内置函数

4.8Python内置函数
example4.8.1

>>> #返回数字绝对值 abs（）>>> abs(-520)520>>> abs

example4.8.2

>>>#返回最大值和最小值 max（）、min()>>> a = [1,2,3,4,5,520,815]>>> max(a)815>>> min(a)1>>> 

example4.8.3

>>> #求字符串长度len()>>> a = [1,2,3,4,5,520,815]>>> s = 'cuixiaohui'>>> len(s)10>>> len(a)7

example4.8.4

>>> help(divmod)Help on built-in function divmod in module builtins:divmod(...)    divmod(x, y) -> (div, mod)        Return the tuple ((x-x%y)/y, x%y).  Invariant: div*y + mod == x.>>>#求商和模divmod()>>> divmod(2,5)(0, 2)>>> divmod(5,2)(2, 1)>>> divmod(100,100)(1, 0)

example4.8.5

>>> help(pow)Help on built-in function pow in module builtins:pow(...)    pow(x, y[, z]) -> number        With two arguments, equivalent to x**y.  With three arguments,    equivalent to (x**y) % z, but may be more efficient (e.g. for ints).>>> #求次方>>> pow(3,3)27>>> #求次方的模>>> pow(3,3,7)6

example4.8.6

>>> help(round)Help on built-in function round in module builtins:round(...)    round(number[, ndigits]) -> number        Round a number to a given precision in decimal digits (default 0 digits).    This returns an int when called with one argument, otherwise the    same type as the number. ndigits may be negative.>>> round(520)520

example4.8.7

>>> help(callable)Help on built-in function callable in module builtins:callable(...)    callable(object) -> bool        Return whether the object is callable (i.e., some kind of function).    Note that classes are callable, as are instances of classes with a    __call__() method.>>> #判断一个对象是否可以用（函数是否定义）>>> callable(f)Traceback (most recent call last):  File "<pyshell#52>", line 1, in <module>    callable(f)NameError: name 'f' is not defined>>> def f(x):if x< 0:return  -xreturn x>>> callable(f)True

example4.8.8

>>> help(isinstance)Help on built-in function isinstance in module builtins:isinstance(...)    isinstance(object, class-or-type-or-tuple) -> bool        Return whether an object is an instance of a class or of a subclass thereof.    With a type as second argument, return whether that is the object's type.    The form using a tuple, isinstance(x, (A, B, ...)), is a shortcut for    isinstance(x, A) or isinstance(x, B) or ... (etc.).>>> #判断某一对象的类型>>> a=[1, 2, 3, 4, 5, 520, 815]>>> type(a)<class 'list'>>>> isinstance(a,list)True>>> isinstance(a,int)False>>> 

example4.8.9

#cmp()在python3.3.3未定义>>> help(cmp)Traceback (most recent call last):  File "<pyshell#64>", line 1, in <module>    help(cmp)NameError: name 'cmp' is not defined>>> cmp('lixiaotao','lixiao')Traceback (most recent call last):  File "<pyshell#65>", line 1, in <module>    cmp('lixiaotao','lixiao')NameError: name 'cmp' is not defined>>> #cmp()是比较两个字符串是否一样#假设已经定义，举例如下>>> cmp('hello','hello')0>>> cmp('h','hello')-1>>> cmp('hhhhhhh','hello')1

example4.8.10

#快速生成一个序列range（）#xrange（）在python3.3.3未定义>>> range(10)range(0, 10)>>> help(range)Help on class range in module builtins:class range(object) |  range(stop) -> range object |  range(start, stop[, step]) -> range object |   |  Return a virtual sequence of numbers from start to stop by step. |   |  Methods defined here: |   |  __contains__(...) |      x.__contains__(y) <==> y in x |   |  __eq__(...) |      x.__eq__(y) <==> x==y |   |  __ge__(...) |      x.__ge__(y) <==> x>=y |   |  __getattribute__(...) |      x.__getattribute__('name') <==> x.name |   |  __getitem__(...) |      x.__getitem__(y) <==> x[y] |   |  __gt__(...) |      x.__gt__(y) <==> x>y |   |  __hash__(...) |      x.__hash__() <==> hash(x) |   |  __iter__(...) |      x.__iter__() <==> iter(x) |   |  __le__(...) |      x.__le__(y) <==> x<=y |   |  __len__(...) |      x.__len__() <==> len(x) |   |  __lt__(...) |      x.__lt__(y) <==> x<y |   |  __ne__(...) |      x.__ne__(y) <==> x!=y |   |  __reduce__(...) |   |  __repr__(...) |      x.__repr__() <==> repr(x) |   |  __reversed__(...) |      Return a reverse iterator. |   |  count(...) |      rangeobject.count(value) -> integer -- return number of occurrences of value |   |  index(...) |      rangeobject.index(value, [start, [stop]]) -> integer -- return index of value. |      Raise ValueError if the value is not present. |   |  ---------------------------------------------------------------------- |  Data descriptors defined here: |   |  start |   |  step |   |  stop |   |  ---------------------------------------------------------------------- |  Data and other attributes defined here: |   |  __new__ = <built-in method __new__ of type object> |      T.__new__(S, ...) -> a new object with type S, a subtype of T>>> help(xrange)Traceback (most recent call last):  File "<pyshell#68>", line 1, in <module>    help(xrange)NameError: name 'xrange' is not defined

example4.8.11
类型转化函数
type（）
int（）
long()
float()
complex() 复数

>>>#举例>>> s='520'>>> type(s)<class 'str'>>>> s + 520Traceback (most recent call last):  File "<pyshell#75>", line 1, in <module>    s + 520TypeError: Can't convert 'int' object to str implicitly>>> int(s)520>>> int(s) + 5201040>>> 

example4.8.12
类型转化函数
str()
list()
tuple()
hex()
oct()
chr()
ord()

>>> help(hex)Help on built-in function hex in module builtins:hex(...)    hex(number) -> string        Return the hexadecimal representation of an integer.>>> help(oct)Help on built-in function oct in module builtins:oct(...)    oct(number) -> string        Return the octal representation of an integer.>>> help(chr)Help on built-in function chr in module builtins:chr(...)    chr(i) -> Unicode character        Return a Unicode string of one character with ordinal i; 0 <= i <= 0x10ffff.>>> help(ord)Help on built-in function ord in module builtins:ord(...)    ord(c) -> integer        Return the integer ordinal of a one-character string.>>> 

注：学习内容来源于网易云课堂《疯狂的Python：快速入门精讲》；代码执行环境为Win；Python版本为 3.3.3