pyparsing.py 文件源码

def pop( self, *args, **kwargs):
        """
        Removes and returns item at specified index (default=C{last}).
        Supports both C{list} and C{dict} semantics for C{pop()}. If passed no
        argument or an integer argument, it will use C{list} semantics
        and pop tokens from the list of parsed tokens. If passed a 
        non-integer argument (most likely a string), it will use C{dict}
        semantics and pop the corresponding value from any defined 
        results names. A second default return value argument is 
        supported, just as in C{dict.pop()}.

        Example::
            def remove_first(tokens):
                tokens.pop(0)
            print(OneOrMore(Word(nums)).parseString("0 123 321")) # -> ['0', '123', '321']
            print(OneOrMore(Word(nums)).addParseAction(remove_first).parseString("0 123 321")) # -> ['123', '321']

            label = Word(alphas)
            patt = label("LABEL") + OneOrMore(Word(nums))
            print(patt.parseString("AAB 123 321").dump())

            # Use pop() in a parse action to remove named result (note that corresponding value is not
            # removed from list form of results)
            def remove_LABEL(tokens):
                tokens.pop("LABEL")
                return tokens
            patt.addParseAction(remove_LABEL)
            print(patt.parseString("AAB 123 321").dump())
        prints::
            ['AAB', '123', '321']
            - LABEL: AAB

            ['AAB', '123', '321']
        """
        if not args:
            args = [-1]
        for k,v in kwargs.items():
            if k == 'default':
                args = (args[0], v)
            else:
                raise TypeError("pop() got an unexpected keyword argument '%s'" % k)
        if (isinstance(args[0], int) or 
                        len(args) == 1 or 
                        args[0] in self):
            index = args[0]
            ret = self[index]
            del self[index]
            return ret
        else:
            defaultvalue = args[1]
            return defaultvalue