7.24 python日学 字符串函数及操作

1.字符串索引

a=‘123abc’

print(a[0],a[1])

i=0

while i<len(a):

print(i)

i+=1

for i in range(len(a)):

print(a[i])

2.切片

a=‘123abcd’

b=‘123456789’

b=a[0:5]

print(b)

print(a[3:])

print(a[:5])

print(a[:])

print(a[::3])

print(a[3::3])

print(a[:4:3])

print(a[3:0:-1])

print(a[::-1])

print(a[-1:-5:-2])

print(b[-8:5])

print(b[0:-7])

print(b[-1:-5:-1])

3.字符串拼接，+ *

a=‘我爱你’

b=‘北京’

c=a+b

print©

a=‘你好’*3

print(a)

a,b,*c=‘12345’

print(a)

print(b)

print©

4.字符串函数

a=‘abcdefcdg’

b=‘cd’

print(a.find(b))

print(a.find(‘zz’))

print(a.rfind(b))

print(a.index(b))

print(a.index(‘cdx’))

print(a.rindex(b))

print(a.count(b))

5.字符串拆分

a=‘123ab456ab789’

print(a.partition(‘ab’))

b=a.split(‘a’)

print(b)

a=‘2019-07-24’

print(a.split(’-’))

a=‘abc\n123\n45’

b=a.splitlines()

print(b)

print(a.split(’\n’))

6.字符串替换

a=‘123abc456abc’

b=a.replace(‘abc’,‘xy’)

print(b,a)

s=‘1234567890111’

a=‘1234567’

b=‘abcdefg’

table=str.maketrans(a,b)

b=s.translate(table)

print(b)

7.字符串修饰

a=‘123’

b=a.center(7,’*’)

print(b)

b=a.ljust(10,’$’)

print(b)

b=a.rjust(10,’$’)

print(b)

b=a.zfill(10)

print(b)

a=’ 123 ’

b=a.lstrip()

print(b,end=’/’)

b=a.rstrip()

print(b,end=’/’)

b=a.strip()

print(b,end=’/’)

a=’###123####’

b=a.lstrip(’#’)

print(b)

b=a.rstrip(’#’)

print(b)

b=a.strip(’#’)

print(b)

8.字符串格式化

a=‘我叫{},年龄{}’.format(‘张三’,29)

print(a)

a=‘我叫{0}，姓名{0}，年龄{1}，姓名{1}’.format(‘李四’,29)

print(a)

print(‘我叫{name},年龄{age},姓名{name}’.format(name=‘张三’,age=30))

a=‘我叫{:#<8}’.format(‘赵六’)

print(a)

a=‘我叫{:！>8}’.format(‘赵六’)

print(a)

a=‘我叫{:&^8}’.format(‘赵六’)

print(a)

“”"
^居中 ， <居左 ，>居右
: 后面是填充字符

是填充的字符，也可以是其他的字符

8 字符总长度，可以换成其他数字，不足的用填充字符填充
“”"
9.字符串变形

a=‘abcABC’

b=a.upper()

print(b)

b=a.lower()

print(b)

b=a.swapcase()

print(b)

a=‘what is your name’

print(a.title())

print(a.capitalize())

a=‘123\t456\txx’

print(a.expandtabs())

10.字符串判断

a=‘123’

print(a.isdigit())

a=‘123d’

print(a.isdigit())

a=‘azAs’

print(a.isalpha())

a=‘a12fcf’

print(a.isalpha())

a=‘123aza’

print(a.isalnum())

a=‘123az-’

print(a.isalnum())

a=‘abc’

print(a.islower())

a=‘abcA’

print(a.islower())

a=‘ABC’

print(a.isupper())

a=‘ABCa’

print(a.isupper())

a=‘What Is Your Name’

print(a.istitle())

a=‘what is your name’

print(a.istitle())

a=’ ’

print(a.isspace())

a=’ 1’

print(a.isspace())

11.dir（）和help（）

a=‘1123’

print(dir(a))#列出字符串对象所有方法的名称

#help来查看函数的具体介绍
12.字符串编码

a=‘1a我’

b=a.encode()

print(b)

c=b.decode()

print©

13.转义字符

a=‘abc’

print(dir(a))

print(help(a.replace))

a=‘tom’s cat’

b=“tom’s cat”

print(a)

print(b)

a=‘E:\test\nex.txt’

print(a)

a=‘E:\test\nex.txt’

print(a)

a=1

b=2

if a>3 \

and b<4:

print(‘adaddd’)

print(’\c’)

print(’\n’)

print(’\t’)

print(’\’)

print(’’’)

print(’"’)

a=r’E:\test\nex.txt’

print(a)

14.元字符串

a=r’E:\test\nex.txt’

print(a)