Default argument value is mutable 这是因为,在Python中,当函数参数使用可变类型(如列表、字典、集合等)作为默认值时,可能会遇到一个问题,即这些默认值在函数被多次调用时可能会被意外修改。这是因为Python在函数定义时计算一次默认值,并在之后的调用中重复使用这些默认值,而不是每次调用时都重新创建它们。 示例问题 考虑以下示
2、The Python Tutorial The default value is evaluated only once. This makes a difference when the default is a mutable object such as a list, dictionary, or instances of most classes. For example, the following function accumulates the arguments passed to it on subsequent calls 解决方案: 参考...
python 函数里面使用[]作为默认参数时,会提示Default Argument Value is mutable(默认参数值是可以改变的) 每次执行函数的时候,可能会不断累加(如果函数里面有append或extend方法),这其实不是我们想要的 解决…
default argument is mutable 1. 解释什么是可变默认参数 在Python中,函数定义时可以指定某些参数具有默认值。这些默认值在函数定义时计算一次,并在函数多次调用之间保持不变,除非显式地通过函数调用来覆盖它们。当这些默认值被设置为可变对象(如列表、字典等)时,它们被称为可变默认参数。
警告:Default Argument Value is mutable 产生原因 参数赋值为可变对象(mutableobject),比如list; 函数参数的初值只会被计算一次。 参考案例 解决方法
Default argument values are evaluated only once, at function definition. Consequently, any modification to that value will affect all subsequent calls. def set_draw_airports(self, value, port_type=["small_airport"], reload=True): def set...
The most useful form is to specify a default value for one or more arguments. This creates a function that can becalled with fewer argumentsthan it is defined to allow. For example: 最有用的形式就是对一个或多个参数指定( specify )一个 预设值 (default value)。这样就会构建一个相比调用定义...
theappendfunction would return a new list every time that the function is called without the second argument. In reality this is not what happens. The first time that the function is called, Python creates a persistent list. Every subsequent call toappendappends the value to that original li...
Documentation The example: dataclasses.html#mutable-default-values @dataclass class D: x: list = [] # This code raises ValueError def add(self, element): self.x += element not only raises the ValueError being discussed, but also an unwan...
In this part you will learn about Python default function arguments to specify a default value for an argument if no value is provided when the function is called, simplifying function calls and...