str.join() 相当于通用可迭代对象

Question

如何实现像这样的

join()

函数？

>>> separator = [')', '-a', '(']
>>> args = [['-name', '*.py'], ['-type', 'f'], ['-mtime', '0']]
>>> list(join(separator, args))
["-name", "*.py", ")", "-a", "(", "-type", "f", ")", "-a", "(", "-mtime", "0"]

Answer 1

def join(sep, iterable):
    iterator = iter(iterable)
    yield from next(iterator)
    for i in iterator:
        yield from sep
        yield from i