004-lambda.py

语法

lambda_expr ::= lambda [parameter_list]: expression

官方文档介绍:

Lambda expressions (sometimes called lambda forms) are used to create anonymous functions.
Similar to block or closure expression in other programming languages, lambda expressions can be used to create small, one-time functions that are not bound to a name.
Note: If you have a complex function that requires multiple expressions or statements, use a def statement instead of a lambda expression.s

简单说:
1. 匿名函数
2. 只有一句代码
3. 通常在需要函数作为参数的情况下使用

# lambda_expr_nocond example
lambda_expr_nocond = lambda x: x * 2
print(lambda_expr_nocond(5))  # Output: 10
print(lambda_expr_nocond(3))  # Output: 6

# 多个参数
x = lambda a, b, c: a + b + c
print(x(5, 6, 2))  # Output: 13

# 将函数与内置函数一起使用
numbers = [1, 2, 3, 4, 5]
squared_numbers = list(map(lambda num: num ** 2, numbers))
print(squared_numbers)  # Output: [1, 4, 9, 16, 25]

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

应用场景:

比如在PyQt 在信号传值的时候，可以使用lambda 匿名函数进行传递

参考个人工程

在项目中

def check_uop(self, sn):
				### ... code omited ...
        uop_thread.finished.connect(lambda response_text: check_uop_finish(self, response_text))
        uop_thread.start()
        ### ... code omited ...


    def check_uop_finish(self, res):
        status = False
        ### ... code omited ...

上述代码中connect(...)需要函数名称作为参数，但是需要调用的函数需要参数；此时可以使用lambda匿名一个新函数来完成参数传递