python学习笔记（四）字符串及字符串操作

字符串

　　字符串可以存任意类型的字符串，比如名字，一句话等等。

字符串还有很多内置方法，对字符串进行操作，常用的方法如下：

 name1='hello world'
 print(name.capitalize())#首写字母大写
 print(name1.capitalize())#首写字母大写Hello world
 print(name1.center(50,'-'))#50个-，把name1放中间-------------------hello world--------------------
 print(name.endswith('u'))#是否以x结尾 False
 print(name1.endswith('d'))#是否以x结尾 True
 print(name.expandtabs(30))#补入\t的次数my                             name is {name},age is{age}.
 print(name1.find('n'))#查找字符串的索引5(\t代表3个字符)
 print(name.format(name='niuniu',age=18))#这个是格式字符串my      name is niuniu,age is18.
 print(name.format_map({'name':'niuniu','age':19}))#这个也是格式化字符串，后面跟的是一个字典，字典在后面也会写
 #my      name is niuniu,age is19.
 print('abA123'.isalnum())#是否包含数字和字母 True
 print('abA'.isalpha())#是否有英文字母True

 name = 'My \t name is {name},age is{age}.'
 print(''.isdigit())#是否有数字True
 print('aa'.isidentifier())#是否是一个合法的变量名True
 print('aa'.islower())#是否是小写字母True
 print('AA'.isupper())#是否是大写字母True
 print('Loadrunner Book'.istitle())#是不是一个标题，判断首字母是否大写True
 print('+'.join(['hehe','haha','ee']))#拼接字符串 hehe+haha+ee
 print(name.lower())#变成小写my      name is {name},age is{age}.
 print(name.upper())#变成大写MY      NAME IS {NAME},AGE IS{AGE}.
 print('\nmysql \n'.lstrip())#默认去掉左边的空格和换行
 print('\nmysql \n'.rstrip())#默认去掉右边的空格和换行
 print('\nmysql \n'.strip())#默认去掉两边的空格和换行
 p=str.maketrans('abcdefg','')#前面的字符串和后面的字符串做映射
 print('cc ae gg'.translate(p))#输出按照上面maketrans做映射后的字符串33 15 77

 new_p=str.maketrans('','abcdefg')
 print('cc ae gg'.translate(new_p))
 print('mysql is db.'.replace('mysql','oracle',1))#替换字符串oracle is db.
 print('mysql is db.mysql is db.mysql is db.'.replace('mysql','oracle',2))#替换字符串oracle is db.oracle is db.mysql is db.
 print('mysql is is db'.rfind('is'))#返回最右边字符的下标 9
 print('1+2+3+4'.split('+'))#切割字符串，返回一个list ['1', '2', '3', '4']
 print('1+2+3\n1+2+3+4'.splitlines())#按照换行符分割['1+2+3', '1+2+3+4']
 print('Abcdef'.swapcase())#大小写反转aBCDEF