字符串的去重操作

笔记

s='helloworldhelloworldssgnjaghlhglhaslgh'
# (1)字符串拼接及not in
new_s=''
for item in s:
    if item not in new_s:
        new_s+=item # 拼接操作
print(new_s)

# 使用索引+not in
new_s2=''
for i in range(len(s)):
    if s[i] not in new_s2:
        new_s2+=s[i]
print(new_s2)

# 通过集合去重+列表排序
new_s3=set(s)
lst=list(new_s3)
lst.sort(key=s.index)
print(''.join(lst))