Python filter | Map | reduce | Use of Lambda __python

1.filter (function, sequence): performs a function (item) on the item in sequence, and makes an item that executes the result to true list/string/ Tuple (depending on the type of sequence) returns:

>>> def f (x): return x 2!= 0 and x 3!= 0 
>>> filter (F, Range (2,)) 
[5, 7, 11, 13, 17, 19 ,
>>> def f (x): return x!= ' a ' 
>>> filter (F, "abcdef") 
' Bcdef '

2.map (function, sequence):Perform a function (item) in sequence on the item in sequence, see the Execution results form a list return:

>>> def Cube (x): return x*x*x 
>>> map (cube, range (1, one)) 
[1, 8, 27, 64, 125, 216, 343, 512, 729 , 1000]
>>> def Cube (x): return x + x 
... 
>>> map (Cube, "ABCDE") 
[' AA ', ' BB ', ' cc ', ' dd ', ' ee ']
Another map also supports multiple sequence, This requires that the function also supports the corresponding number of parameter inputs:
>>> def add (x, y): return x+y 
>>> map (Add, Range (8), range (8)) C16/>[0, 2, 4, 6, 8, 10, 12, 14]

3.reduce (function, sequence, starting_value):The call function is iterated over the item order in sequence and, if there is a starting_value, it can be invoked as an initial value, for example, to sum the list:

>>> def Add (x,y): return x + y 
>>> reduce (add, range (1, one)) 
55 (note: 1+2+3+4+5+6+7+8+9+10)
& gt;>> reduce (Add, range (1, a) 
75 (note: 1+2+3+4+5+6+7+8+9+10+20)

4.lambda:This is a very interesting syntax that Python supports, which allows you to quickly define the smallest function of a single line, similar to a macro in C, these functions called Lambda are borrowed from Lisp and can be used wherever a function is needed:

>>> g = Lambda x:x * 2 
>>> g (3) 
6 
>>> (Lambda x:x * 2) (3) 
6

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Reference: http://www.cnblogs.com/longdouhzt/archive/2012/05/19/2508844.html