Python function Learning: lambda (), filter (), map (), reduce ()

1. Lambda ()

A lambda () is an anonymous function in Python with the following syntax:

Lambda [arg1[, arg2, ... argn]]: expression

Here's an example of a 1+2=3.

>>> fun = Lambda x,y:x+y

>>> Fun (1,2)

3

>>> (lambda x,y:x+y) (1,2)

3

2, filter ()

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, 25))

[5, 7, 11, 13, 17, 19, 23]

>>> def f (x): return x!= ' a '

>>> filter (F, "abcdef")

' Bcdef '

3, Map ()

Map (function, sequence): Performs 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, 11))

[1, 8, 27, 64, 125, 216, 343, 512, 729, 1000]

>>> def Cube (x): return x + x

...

>>> map (Cube, "ABCDE")

[' AA ', ' BB ', ' cc ', ' dd ', ' EE ']

The map also supports multiple sequence, which 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))

[0, 2, 4, 6, 8, 10, 12, 14]