python字符串切片常用方法有哪些

str = 'abcdefg_a'
print(str[1:6:2], str[2:6], str[:3], str[3:], str[:])
print(str[::2], str[:-2], str[-6:-2], str[::-2], str[::-1])
print(str[-2:], str[2:-2], str[-2::-2], str[:-2:2], str[2:-2:2])
 
输出：
bdf cdef abc defg_a abcdefg_a
acega abcdefg defg ageca a_gfedcba
_a cdefg _fdb aceg ceg

str = 'abcdefg_a'
print('-------------------查找-------------------')
print(str.find('c'), str.find('fg', 2, ), str.find('a', 2), str.find('h'))
print(str.index('c'), str.index('fg', 2, ), str.index('a', 2))
print(str.find('a'), str.rfind('a'), str.index('a'), str.rindex('a'), str.count('a'))
print(str.index('h'))
 
输出：
-------------------查找-------------------
2 5 8 -1
2 5 8
0 8 0 8 2
ValueError: substring not found

print('--------------修改--------------')
str1 = 'hello python and hello IT and hello world and hello YX !'
print(str1.replace('and','&&'))
print(str1.split('and'), str1.split('and', 2))
l = ['Hello', 'world', '!']
t = ('Hello', 'python', '!')
print('_'.join(l), ' '.join(t))  # 用下划线_和空格连接
print(str1.capitalize())  # 首字符转为大写，其余均小写
print(str1.title())  # 每个单词首字母转为大写
str2 = '   Hello World !   '
print(str2.lower(), str2.upper(), str2.swapcase())  # 大写转小写，小写转大写，翻转大小写
print(str2.partition('rl'), str2.partition('o'))  # 根据指定分隔符将字符串分割，返回三元元组
print(min(str2), max(str2), ord(min(str2)), ord(max(str2)))  # str2中最小为空格对应十进制32，最大为r对应114
print(str2.zfill(21))  # 输出指定长度为21的字符串，右对齐，不足前面补0，超出指定长度则原样输出
print(str2.lstrip(), str2.rstrip(), str2.strip())  # 清除字符串左、右、两边空格字符
str3 = 'hello!'
print(str3.ljust(13, '*'), str3.rjust(13, '*'), str3.center(14, '*'))
 
输出：
--------------修改--------------
hello python && hello IT && hello world && hello YX !
['hello python ', ' hello IT ', ' hello world ', ' hello YX !'] ['hello python ', ' hello IT ', ' hello world and hello YX !']
Hello_world_! Hello python !
Hello python and hello it and hello world and hello yx !
Hello Python And Hello It And Hello World And Hello Yx !
   hello world !       HELLO WORLD !       hELLO wORLD !   
('   Hello Wo', 'rl', 'd !   ') ('   Hell', 'o', ' World !   ')
  r 32 114
00   Hello World !  
Hello World !       Hello World ! Hello World !
hello!******* *******hello! ****hello!****

print('---------------判断----------------')
str3 = 'hello!'
print(str3.startswith('he'), str3.startswith('she'), str3.startswith('he',2,))
print(str3.endswith('!'), str3.endswith('。'), str3.endswith('!', 2, 5))
print(str3.isalpha(),str3.isalnum(), str3.isdigit(), str3.isspace())
 
输出：
---------------判断----------------
True False False
True False False
False False False False