python字符串操作

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转载最新推荐文章于 2025-08-23 20:28:56 发布 · 75 阅读

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原文链接：http://www.cnblogs.com/navy2013/p/9729471.html

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#python

1 切片操作

>>> str="hello world!"
>>> str[1:3]
'el'
>>> str[:3]
'hel'
>>> str[2:]
'llo world!'

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2 不能直接改变字符串的值，更新字符串可以利用切片

>>> str="hello world!"
>>> str1=str[:1]+'python'+str[1:]
>>> str1
'hpythonello world!'

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3 capitalize(): 将字符串第一个字符大写

>>> str='hello world!'
>>> str.capitalize()
'Hello world!'

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4 casefold(): 将整个字符串小写

>>> str1="Hello world!"
>>> str1.casefold ()
'hello world!'

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5 center(width) 将整个字符串居中（如果不够width则用空格补充）

>>> str="Hello world!"
>>> str.center(20)
'    Hello world!

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6 count(sub[,start[,end]]) sub从start到end出现的次数(默认是整个字符串),不包括end项

>>> str="Hello world!"
>>> str.center(20)
'    Hello world!    '
>>> str="Hello world!"
>>> str.count('l',3)
2
>>> str.count('l')
3
>>> str.count('l',3,6)
1
>>> str.count('l',1,3)
1
>>> str.count('l',1,4)
2

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7 endswith(sub)判断是否是以哪个字符串结尾

>>> str="Hello world!"
>>> str.endswith('orld!')
True
>>> str.endswith('orld')
False

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8 expandstabs() 将字符串中的'\t'转换为空格

>>> str2="Hello\tworld!"
>>> str2.expandtabs()
'Hello   world!'
>>> str2="Hello\tworld!"
>>> str2.expandtabs()
'Hello   world!'
>>> str2="Hello\t world!"
>>> str2.expandtabs()
'Hello    world!'
>>> str2="Hello\t  world!"
>>> str2.expandtabs()
'Hello     world!'
>>> str2="Hello\t   world!"
>>> str2.expandtabs() 
'Hello      world!'
>>> str2="Hello\t       world!"
>>> str2.expandtabs() 
'Hello          world!'

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9 find(sub[,start][,end]) 查找字符串中子串从start到end出现的位置并返回下标

>>> str="Hello world!"
>>> str.find('llo')
2
>>> str.find('llo',3,8)
-1
>>> str.find('llo',2,8)
2

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10 isalnum(): 判断是否是数字或字母

>>> str="Hello world"
>>> str.isalnum()
False
>>> str="Helloworld"
>>> str.isalnum()
True
>>> str="Helloworld!"
>>> str.isalnum()
False
>>> str="Hello2f23world"
>>> str.isalnum()
True

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11 isspace(): 判断是否为空格

>>> str="hello world"
>>> str.isspace()
False
>>> str=""
>>> str.isspace()
False
>>> str=" "
>>> str.isspace()
True
>>> str="       "
>>> str.isspace()
True

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12 isdigit() 判断是否为数字

>>> str="1235 6"
>>> str.isdigit()
False
>>> str="12356"
>>> str.isdigit()
True
>>> str="12356!"
>>> str.isdigit()
False

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13 isalpha(): 判断是否为字母

>>> str="1fjafajfa"
>>> str.isalpha()
False
>>> str="fjafajfa"
>>> str.isalpha()
True
>>> str="fjafaj fa"
>>> str.isalpha()
False

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14 islower() 判断是否都为小写

>>> str="afjajga"
>>> str.islower()
True
>>> str="afjajgJa"
>>> str.islower()
False

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15 isupper() 判断是否都为大写

>>> str="AFJAJGAJF"
>>> str.isupper()
True
>>> str="AFJAJGAJfjF"
>>> str.isupper()
False

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16 istitle(): 判断是否是标题形式字符串（即是连续字符串只有第一个字母大写，其他都是小写，若是有空格，则每个分隔的字符串都满足此）

>>> str="Name Age Address"
>>> str.istitle()
True
>>> str="Name Age AdAdress"
>>> str.istitle()
False
>>> str="Name Age address"
>>> str.istitle()
False

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17 join(sub)

>>> str="abc"
>>> str.join('1234')
'1abc2abc3abc4'
>>> str="-"
>>> str.join("abc")
'a-b-c'

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18 lstrip(): 去掉字符串左边所有的空格

>>> str=" hello world! "
>>> str.lstrip()
'hello world! '

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19 rstrip(): 去掉字符串右边所有的空格

>>> str=" hello world!  "
>>> str.rstrip()
' hello world!'

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20 strip(): 去掉字符串左右两边所有空格

>>> str=" hello world!  "
>>> str.strip()
'hello world!'

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21 replace(old,[,new][,count]); 将字符串中的old子串替换为new,替换count次

>>> str="this is string exampel....wow!!! this is really string"
>>> str.replace("is","was")
'thwas was string exampel....wow!!! thwas was really string'
>>> str.replace("is","was",3)
'thwas was string exampel....wow!!! thwas is really string'

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22 rfind(sub[,start][,end]) : 从右边开始查找字符串中子串从start到end出现的位置并返回下标（注意start和end是从左往右的，返回的也是从左往右的位置，异常返回-1）

>>> s1="this is really a string example....wow!!!"
>>> s2="is"
>>> s1.rfind(s2)
5
>>> s1.rfind(s2,0,10)
5
>>> s1.rfind(s2,10,0)
-1
>>> s1.rfind(s2)
5
>>> s1.find(s2)
2
>>> s1.find(s2,0,10)
2
>>> s1.find(s2,10,0)
-1

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23 swapcase()：将字符串的大小写反转

>>> str="Hello World!"
>>> str.swapcase()
'hELLO wORLD!'
>>>

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24 split(seq)：通过指定分隔符对字符串进行切片，如果参数 num 有指定值，则仅分隔 num 个子字符串，返回分割后的字符串列表。

>>> str="Line1-abcdef \nLine2-abc \nLine4-abcd"
>>> str.split()
['Line1-abcdef', 'Line2-abc', 'Line4-abcd']
>>> str.split(' ',1)
['Line1-abcdef', '\nLine2-abc \nLine4-abcd']

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25 startwith(sub[,start][,end])：判断从start到end是否以sub开头

>>> str="hello world"
>>> str.startswith("he")
True
>>> str.startswith("h")
True
>>> str.startswith(" h")
False

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26 title() 将字符串标题化（即是连续字符串的第一个字母大写，其他都是小写空格，分隔的字符串都遵循此规则）

>>> str="name age address"
>>> str.title()
'Name Age Address'

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27 tanslate(table)　　Python translate() 方法根据参数table给出的表(包含 256 个字符)转换字符串的字符, 要过滤掉的字符放到 del 参数中。

intab="aeiou"
outtab="12345"
deltab="thw"

trantab1=str.maketrans(intab,outtab) #创建字符映射转换表
trantab2=str.maketrans(intab,outtab,deltab) #创建字符映射转换表，并删除指定字符

test="this is string example....wow!!!"

print(test.translate(trantab1))

--------结果---------
th3s 3s str3ng 2x1mpl2....w4w!!!
3s 3s sr3ng 2x1mpl2....4!!!

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28 upper()：将字符串转换成大写

>>> str="Hello World!"
>>> str.upper()
'HELLO WORLD!'

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29 lower()：将字符串转换成小写

>>> str="Hello World!"
>>> str.lower()
'hello world!'

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30 zfill(width)：返回指定长度的字符串，原字符串右对齐，前面填充0。

>>> str="hello world!"
>>> str.zfill(20)
'00000000hello world!'

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31 format() 通过 {} 和 : 来代替以前的 %，增强了字符串的格式化功能

#通过位置
print("{0},{1}".format('chuhao',20))
print("{},{}".format('chuhao',20))
print("{1},{0},{1}".format('chuhao',20))

#通过关键字参数
print("{name},{age}".format(age=18,name="chuhaho"))

class Person:
    def __init__(self,name,age):
        self.name=name
        self.age=age

    def __str__(self):
        return  "This guy is {self.name},is {self.age} old".format(self=self)
print(Person("chuhao",18)) #返回type类型是类
print(str(Person("chuhao",18))) #返回type类型是字符串

#通过映射list
a_list=['chuhao',20,'china']
print("my name is {0[0]},from {0[2]},age is {0[1]}".format(a_list))

#通过映射dict
b_dict={'name':'chuhao','age':20,'province':'jiangxi'}
print("my name is {name},age is {age},from {province}".format(**b_dict))

#填充与对齐
print("{:>8}".format("189"))
print("{:0>8}".format("189"))
print("{:a>8}".format("189"))

#精度与类型（保留2位小数）
print("{:.2f}".format(321.33345))

#用来作为金额的千位分隔符
print("{:,}".format(1234567890))

#其他类型
print("{:b}".format(18))
print("{:d}".format(18))
print("{:o}".format(18))
print("{:x}".format(18))

--------结果--------
chuhao,20
chuhao,20
20,chuhao,20
chuhaho,18
This guy is chuhao,is 18 old
This guy is chuhao,is 18 old
my name is chuhao,from china,age is 20
my name is chuhao,age is 20,from jiangxi
     189
00000189
aaaaa189
321.33
1,234,567,890
10010
18
22
12

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32 格式化

>>> "%d+%d=%d" %(4,5,4+5)
'4+5=9'
>>> "%c" %97
'a'

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转载于:https://www.cnblogs.com/navy2013/p/9729471.html