Python Learning note __4.3 anonymous function (concise function)

# This is a learning note for the Liaoche teacher Python tutorial

1. Overview

The keyword lambda represents an anonymous function

List (map (lambda x:x * x, [1, 2, 3, 4, 5, 6, 7, 8, 9]))

# The Lambda in the list-building is actually

def f (x):

return x * x

But there is a limit to anonymous functions, that is, there can only be one expression.

Anonymous function does not write return, the return value is the result of the expression

anonymous function because the function has no name, you do not have to worry about the function name conflict.

In addition, the anonymous function is also a function object, You can assign the anonymous function to a variable, and then use the variable to invoke the function, you can also return the anonymous function as a return value

# Anonymous function Assignment variable

>>> f = Lambda x:x * x

>>> F

<function <lambda> at 0x101c6ef28>

>>> F (5)

25

# anonymous function returned as return value

def build (x, y):

return lambda:x * x + y * y

2 , examples

1. Change the following function to anonymous function

#-*-Coding:utf-8-*-

def is_odd (n):

return n% 2 = = 1

L = List (filter (is_odd, Range (1, 20)))

Print (L)

# change

L = List (filter (lambda x:x%2==1, range (1, 20)))

Python Learning note __4.3 anonymous function (concise function)