python经典案例:lambda匿名函数应知应会

问题：lambda匿名函数常用案例

匿名函数（lambda）是一种不需要使用def语句声明的函数，它是一种表达式，主要用于简化代码和避免函数名冲突。

1.计算两个数的和

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
sum_function = lambda x, y: x + y
result = sum_function(3, 5)
print(result)  # 输出：8

2.计算两个数的乘积

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
product_function = lambda x, y: x * y
result = product_function(2, 4)
print(result)  # 输出：8

3.判断一个数是否为偶数

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
is_even_function = lambda x: x % 2 == 0
result = is_even_function(4)
print(result)  # 输出：True

4.反转字符串

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
reverse_string_function = lambda s: s[::-1]
input_string = "nohtyp"
result = reverse_string_function(input_string)
print(result)  # 输出：python

5.计算阶乘

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
factorial_function = lambda n: 1 if n == 1 else n * factorial_function(n - 1)
num = 5
result = factorial_function(num)
print(result)  # 输出：120

6.使用匿名函数作为map和filter的参数

#!/usr/bin/python
#coding:utf-8
#author:菜就多练呀
# 计算列表中每个元素的平方
square_function = lambda x: x ** 2
squares = list(map(square_function, [1, 2, 3, 4, 5]))
print(squares)  # 输出：[1, 4, 9, 16, 25]

# 过滤出列表中小于3的元素
less_than_three_function = lambda x: x < 3
less_than_three_elements = list(filter(less_than_three_function, [1, 2, 3, 4, 5]))
print(less_than_three_elements)  # 输出：[1, 2]

请注意，匿名函数仅限于包含一个表达式，并且不需要返回语句。