How to use lambda function in python

The lambda function in Python is an anonymous function, also called an inline function or function literal. Can be used to create simple, one-line functions, usually when a function is needed, but only used once, and does not need to be named. The basic syntax of a lambda function is "lambda arguments: expression".

The operating system for this tutorial: Windows 10 system, Python version 3.11.4, Dell G3 computer.

In Python, the lambda function is an anonymous function, also called an inline function or function literal. It can be used to create simple, one-line functions, usually when a function is required, but only used once, and does not need to be named.

The basic syntax of the lambda function is as follows:

lambda arguments: expression

Among them, arguments are the parameters of the function, which can be multiple parameters, separated by commas; expression is the return value of the function, usually an expression .

The following are some example usages of lambda functions:

# 一个参数的 lambda 函数
square = lambda x: x**2
print(square(5))  # 输出 25
# 多个参数的 lambda 函数
add = lambda a, b: a + b
print(add(3, 4))  # 输出 7
# 在列表排序中使用 lambda 函数
pairs = [(1, 'one'), (2, 'two'), (3, 'three'), (4, 'four')]
pairs.sort(key=lambda pair: pair[1])
print(pairs)  # 输出 [(4, 'four'), (1, 'one'), (3, 'three'), (2, 'two')]

In the above examples, the lambda function is used to define simple functions and can be used directly without using the def keyword to define the function . Lambda functions are typically used in functional programming, passed as arguments inside functions, or wherever a simple function is required.

It should be noted that lambda functions are usually used to write simple, single-line functions. If the function is more complex, it is recommended to use an ordinary def function to define it.

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