Python Basic learning built-in functions

Built-in functions

Example: If you return the absolute value of a number, the Write function is very inconvenient [[email protected] tools]# python fa.py 10[[email protected] tools]# cat fa.py #!/usr/bin/pythond EF A (x): if x < 0:return-x return x n = a ( -10) print n

#帮助查看 #

>>> Help (Len)

Usage: Help (name of function)

ABS () return absolute value

>>> ABS (-10) 10

Max () returns the maximum value, min () returns the minimum value

>>> l=[1,4,7,12,555,66,]>>> min (l) 1>>> Max (l) 555

Len () gets the string length

>>> s = ' Konglingchao ' >>> len (s) 12

Divmod () seeking for remainder usage: divmod (divisor, divisor)

>>> Divmod (10,2) (5, 0)

pow () Operation usage: POW (number 1, number 2,/(number 3)) number 3 optional

>>> Pow (3,3) 27>>> pow (3,3,2) 1

Round () return floating-point number

>>> round (1112) 1112.0

Callable () tests whether a function is defined

>>> callable (min) True #函数定义返回True >>> callable (f) Traceback (most recent call                 Last): File "<stdin>", line 1, in <module>nameerror:name ' F ' are not defined #函数未被定义 >>> f=100 #f是一个变量 >>> callable (f) False #返回True

Isinstance ()

>>> print L[1, 4, 7, 555, 66]>>> print f<function f at 0x1a1e320>>>> type (f) <type ' function ' >>>> type (l) <type ' list ' > >>> if Type (l) ==type ([]):. print ' OK ' ... ok #判断 Whether to use Isinstance for the list to determine an object type >>> isinstance (l,int) false>>> isinstance (L,STR) false>>> Isinstance (l,list) True

CMP () string comparison

>>> CMP ("7", "7") 0>>> CMP ("7", "M") -1>>> CMP ("7", "6") 1

Range () Fast sequence generation

>>> Range (10) [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Xrange () can be understood as an object with a higher efficiency than range

>>> x = xrange (Ten) >>> print Xxrange (10)

Functions for data Conversion types:

int () integer

Long () length shaping

Float () Float type

Complex () plural type

STR ()

List ()

Tuple ()

>>> l=[1,2,3,4]>>> Tuple (L) (1, 4, 7, 12, 555, 66)

Note: The conversion of data should be selective

>>> s= ' Hello ' >>> int (s) Traceback (most recent call last): File "<stdin>", line 1, in <MODULE&G T Valueerror:invalid literal for int. () with base: ' Hello ' >>> s= ' 123 ' >>> type (s) <type ' str ' >> >> Int (s) 123

String function: function is limited to manipulation of strings

#查看帮助要 Add a function to the category:>>> Help (Str.replace)

Str.capitalize (): Capitalize first letter

>>> s= ' Hello ' >>> str.capitalize (s) ' Hello ' >>> s ' Hello word ' >>> s.capitalize () # S is the object in the string, s calls the Capitalize function ' Hello word '

str.replace (): Replace,(you can specify the number of replacements)

>>> s.replace (' Hello ', ' good ') ' good word ' >>> s ' Hello word ' #这里的good word is just a return value and does not change the data directly >> > ss= ' 12121212121212 ' >>> ss.replace (' 1 ', ' xxxxx ') ' xxxxx2xxxxx2xxxxx2xxxxx2xxxxx2xxxxx2xxxxx2 ' >> > Ss.replace (' 1 ', ' xxxxx ', 1) # Specify the number of substitutions ' xxxxx2121212121212 '

Str.split (): Cutting str. Split ("Parameter 1: Cut Suit", "parameter 2 = number of cuts")

>>> ip= "192.168.1.2"
>>> ip.split ('. ')
[' 192 ', ' 168 ', ' 1 ', ' 2 ']
>>> ip.split ('. ', 2)
[' 192 ', ' 168 ', ' 1.2 ']

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Calling methods by importing modules

>>> Import String >>> Help (String.Replace) >>> s ' Hello word ' >>> string.replace (S, ' Hello ', ' good ') ' good word '

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Sequence processing functions

Len ()

Max ()

Min ()

#使用序列函数求数字的长度是无法使用的!!!!!

>>> Len (123) Traceback (most recent): File "<stdin>", line 1, in <module>typeerror:object of type ' int ' has no Len () >>>

Filter (Parameter 1: function, parameter 2: sequence)

Help on built-in function filter in module __builtin__:
Filter (...)
Filter (function or None, sequence), list, tuple, or string
#函数 or #空 sequence
Return those items of sequence for which function (item) is true. If
function is None, and return the items is true. If sequence is a tuple
or string, return the same type, else return a list.

Example:

>>> def f (x): ... if x>5: ... return True ... >>> f (Ten) true>>> F (3) >>> l=r Ange >>> l[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]>>> Filter (f,l) [6, 7, 8, 9]# f function on List L

zip, map () List traversal

>>> name=[' Milo ', ' Zou ', ' Tom ']>>> age=[20,30,40]>>> tel=[' 133 ', ' 144 ', ' 155 ']>>> zip (Name,age,tel) [(' Milo ', 20,  ' 133 '),  (' Zou ', 30,  ' 144 '),   (' Tom ', 40,  ' 155 ')] #并行遍历 >>> map (None,name,age,tel) [(' Milo ', 20,  ' 133 ') ,  (' Zou ', 30,  ' 144 '),  (' Tom ', 40,  ' 155 ')]>>> test=[' A ', ' B ']# If the value of one of the lists is less than the other list, it traverses the shortest list, >>> zip (name,age,tel,test) [(' Milo ', 20,  ' 133 ',  ' a ') ,  (' Zou ', 30,  ' 144 ',  ' B ')] if swapped for a map traversal, it fills the missing value of a list with none. >>> map (None,name,age,tel,test) [(' Milo ', 20,  ' 133 ',  ' a '),  (' Zou ',  30,   ' 144 ',  ' B '),  (' Tom ', 40,  ' 155 ',  none)] #此处的None也可以变为函数, the value of the subsequent operation. >>> a=[1,4,6,]>>> b=[7,8,9]>>> map (None,a,b) [(1, 7),  (4,  8),  (6, 9)]>>> def mf (x, y):  &NBsp;   print x*y... >>> map (mf,a,b) 73254[none, none, none] 

reduce() recursive operations

>>> def f (x, y): ... return x+y >>> l= (range (1,101)) >>> reduce (f,l) 5050 or use anonymous function >>&G T Reduce (lambda x,y:x+y,l) 5050

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Python Basic learning built-in functions