将函数输入的默认值设置为等于Python中的另一个输入 [英] Setting the default value of a function input to equal another input in Python

问题描述

考虑以下函数，它在Python中不起作用，但我将用它来解释我需要做的事情。

  def exampleFunction（a，b，c = a）：
 ...函数体... 
  

那就是我想给变量 c 赋予与变量 a 相同的值，除非指定了替代值。上面的代码在python中不起作用。有没有办法做到这一点？

谢谢。

解决方案

def exampleFunction（a，b，c = None）：
如果c是None：
c = a
...函数体...


关键字参数的默认值不能是变量（如果是的话，当函数被定义时它会被转换为固定值）。常用于将参数传递给主函数：

  def main（argv =无）：
如果argv是None：
 argv = sys.argv 
  

Consider the following function, which does not work in Python, but I will use to explain what I need to do.

def exampleFunction(a, b, c = a):
    ...function body...

That is I want to assign to variable c the same value that variable a would take, unless an alternative value is specified. The above code does not work in python. Is there a way to do this?

Thank you.

解决方案

def exampleFunction(a, b, c = None):
    if c is None:
        c = a
    ...function body...

The default value for the keyword argument can't be a variable (if it is, it's converted to a fixed value when the function is defined.) Commonly used to pass arguments to a main function:

def main(argv=None):
    if argv is None:
        argv = sys.argv

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