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  • python中将实参变为可选项

    1、

    >>> def a(first,meddle,last):
        b = f"{first} {meddle} {last}"
        return b.title()
    
    >>> a("aaa","bbb","ccc")
    'Aaa Bbb Ccc'
    >>> a("aaa","bbb")   ## 少一个实参报错
    Traceback (most recent call last):
      File "<pyshell#159>", line 1, in <module>
        a("aaa","bbb")
    TypeError: a() missing 1 required positional argument: 'last'
    >>> def a(first,last,meddle = ""):    ## 将一个实参设定为空
        b = f"{first} {meddle} {last}"
        return b.title()
    
    >>> a("aaa","bbb","ccc")
    'Aaa Ccc Bbb'
    >>> a("aaa","ccc")
    'Aaa  Ccc'
    >>> def a(first,last,meddle = None):   ## 讲一个实参设定为None , None等价于 “”。
        b = f"{first} {meddle} {last}"
        return b.title()
    
    >>> a("aaa","ccc","bbb")
    'Aaa Bbb Ccc'
    >>> a("aaa","ccc")
    'Aaa None Ccc'
    >>> def a(first,meddle,last):
        b = f"{first} {meddle} {last}"
        return b.title()
    
    >>> a("aaa","bbb","ccc")
    'Aaa Bbb Ccc'
    >>> a("aaa","ccc")      ## 少一个实参,报错
    Traceback (most recent call last):
      File "<pyshell#171>", line 1, in <module>
        a("aaa","ccc")
    TypeError: a() missing 1 required positional argument: 'last'
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  • 原文地址:https://www.cnblogs.com/liujiaxin2018/p/14510515.html
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