1. list、tuple转成字符串
list、tuple的元素必须都是字符串
通过字符串的join()函数处理，代码如下：
l=["北京","东京","华盛顿","伦敦"]
s=",".join(l)
2. 字符串根据分隔符拆成list
s='北京,东京,华盛顿,伦敦'
l=s.split(",")
#查看l的类型
print(type(l))
3. list转换tuple
l=["北京","东京","华盛顿","伦敦"]
t=tuple(l)
print(t)
print(type(t))
4. tuple转换list
t=("北京","东京","华盛顿","伦敦")
l=list(l)
print(l)
print(type(l))