Python中的Lambda匿名函数

背景

Lambda匿名函数在Python中经常出现，小巧切灵活，使用起来特别方便，但是小编建议大家少使用，最好多写几行代码，自定义个函数。

既然Python中存在Lambda匿名函数，那么小编本着存在即合理的原则，还是介绍一下，本篇文章翻译自《Lambda Functions in Python》，分享出来供大家参考学习

原文地址：https://www.clcoding.com/2024/03/lambda-functions-in-python.html

案例1：基本语法

常规函数

def add(x, y):return x + y

匿名函数

lambda_add = lambda x, y: x + y

调用2种类型函数

print(add(3, 5))   #8
print(lambda_add(3, 5))    #8

案例2：在sorted排序函数中使用匿名函数

students = [("Alice", 25), ("Bob", 30), ("Charlie", 22)]sorted_students = sorted(students, key=lambda student: student[1])print("Sorted Students by Age:", sorted_students)
#Sorted Students by Age: [('Charlie', 22), ('Alice', 25), ('Bob', 30)]

案例3：在filter过滤函数中使用匿名函数

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9]even_numbers = list(filter(lambda x: x % 2 == 0, numbers))print("Even Numbers:", even_numbers)
#Even Numbers: [2, 4, 6, 8]

案例4：在map函数中使用匿名函数

numbers = [1, 2, 3, 4, 5]squared_numbers = list(map(lambda x: x**2, numbers))print("Squared Numbers:", squared_numbers)
#Squared Numbers: [1, 4, 9, 16, 25]

案例5：在max函数中使用匿名函数

numbers = [10, 5, 8, 20, 15]max_number = max(numbers, key=lambda x: -x)print("Maximum Number:", max_number)
#Maximum Number: 5

案例6：在sorted排序函数中，多个排序条件

people = [{"name": "Charlie", "age": 25}, {"name": "Bob", "age": 30}, {"name": "Alice", "age": 25}]sorted_people = sorted(people, key=lambda person: (person["age"], person["name"]))print("Sorted People:", sorted_people)
#Sorted People: [{'name': 'Alice', 'age': 25}, {'name': 'Charlie', 'age': 25}, {'name': 'Bob', 'age': 30}]

案例7：在reduce函数中使用匿名函数

from functools import reducenumbers = [1, 2, 3, 4, 5]
product = reduce(lambda x, y: x * y, numbers)
print("Product of Numbers:", product)
#Product of Numbers: 120

案例8：在条件表达式中使用匿名函数

numbers = [10, 5, 8, 20, 15]filtered_and_squared = list(map(lambda x: x**2 if x % 2 == 0 else x, numbers))print("Filtered and Squared Numbers:", filtered_and_squared)
#Filtered and Squared Numbers: [100, 5, 64, 400, 15]