join
s = 'mumu' s1 = '_'.join(s) # m_u_m_u li = ['mumu', '怪蜀黍', '好看'] s = '+++'.join(li) # mumu+++怪蜀黍+++好看
可以利用join去掉列表输出时的引号，方法如下：
li = ['a', 'b', 'c']
pirnt(li) # ['a', 'b', 'c']
s = ', '.join(li) # a, b, c
print('[' + s + ']') # [a, b, c]
split
s = 'm+u+m+u'
li = s.split('+') # ['m', 'u', 'm', 'u']
join: list ----> str
split: str ----> list