Python如何使用Lambda函数（） _Python函数

本文概述

例子1
例子2
为什么要使用lambda函数？
例子1
例子2
例子3

Python允许我们不以标准方式声明函数, 即使用def关键字。而是使用lambda关键字声明匿名函数。但是, Lambda函数可以接受任意数量的参数, 但是它们只能以表达式形式返回一个值。
匿名函数包含一小段代码。它模拟C和C ++的内联函数, 但不完全是内联函数。
下面给出了定义匿名函数的语法。

lambda arguments : expression

例子1

x = lambda a:a+10 # a is an argument and a+10 is an expression which got evaluated and returned. print("sum = ", x(20))

输出

sum =30

例子2Lambda函数的多个参数

x = lambda a, b:a+b # a and b are the arguments and a+b is the expression which gets evaluated and returned. print("sum = ", x(20, 10))

【Python如何使用Lambda函数（）】输出

sum =30

为什么要使用lambda函数？当我们在另一个函数中匿名使用lambda函数的主要角色时, 可以在场景中更好地描述它们。在python中, lambda函数可用作自变量, 而高阶函数可用作自变量。在需要考虑以下示例的情况下, 也可以使用Lambda函数。
例子1

#the function table(n) prints the table of n def table(n): return lambda a:a*n; # a will contain the iteration variable i and a multiple of n is returned at each function call n = int(input("Enter the number?")) b = table(n) #the entered number is passed into the function table. b will contain a lambda function which is called again and again with the iteration variable i for i in range(1, 11): print(n, "X", i, "=", b(i)); #the lambda function b is called with the iteration variable i,

输出

Enter the number?10 10 X 1 = 10 10 X 2 = 20 10 X 3 = 30 10 X 4 = 40 10 X 5 = 50 10 X 6 = 60 10 X 7 = 70 10 X 8 = 80 10 X 9 = 90 10 X 10 = 100

例子2将lambda函数与过滤器一起使用

#program to filter out the list which contains odd numbers List = {1, 2, 3, 4, 10, 123, 22} Oddlist = list(filter(lambda x:(x%3 == 0), List)) # the list contains all the items of the list for which the lambda function evaluates to true print(Oddlist)

输出

[3, 123]

例子3在地图上使用lambda函数

#program to triple each number of the list using map List = {1, 2, 3, 4, 10, 123, 22} new_list = list(map(lambda x:x*3, List)) # this will return the triple of each item of the list and add it to new_list print(new_list)

输出