Python - Function - Default values of Arguments

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Default Argument Values

The most useful form is to specify a default value for one or more arguments. This creates a function that can be called with fewer arguments than it is defined to allow. For example:
def ask_ok(prompt, retries=4, reminder='Please try again!'):
    while True:
        ok = input(prompt)
        if ok in ('y', 'ye', 'yes'):
            return True
        if ok in ('n', 'no', 'nop', 'nope'):
            return False
        retries = retries - 1
        if retries < 0:
            raise ValueError('invalid user response')
        print(reminder)
This function can be called in several ways:
  • giving only the mandatory argument: ask_ok('Do you really want to quit?')
  • giving one of the optional arguments: ask_ok('OK to overwrite the file?', 2)
  • or even giving all arguments: ask_ok('OK to overwrite the file?', 2, 'Come on, only yes orno!')

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