Python中关于字符串你应该知道这些...

# Python中字符串的常见用法
### 定义：带有双引号/单引号/三引号
### 双引号：适用于所写的字符串里没有双引号的。例如：
"凡是“辛苦”必是礼物"报错
### 单引号：适用于所写的字符串里没有单引号的。例如：
'I'm xiaoming'报错
### 三引号：适用于多行字符串。例如：
''' 灯火星星...人声杳杳...歌不尽乱世烽火'''.上述三行可正常输出
###字符串可以用"" "" "" 、"str1 str2 str3"和("" "" "")以及("str1 str2 str3")表示而("","","")和 "","",""是元组
```
>>> name = "Jerry","Jenny"
>>> type(name)
<class 'tuple'
>>>> name = ("as" "we" "can" "do")
>>> type(name)
<class 'str'
>>>> poems = ("曾经沧海难为水","除去巫山不是云")
>>> type(poems)
<class 'tuple'
>>>> name = "Jack","Keoa","Kim"
>>> name('Jack', 'Keoa', 'Kim')
>>> type(name)
<class 'tuple'
>>>> name = ("as" "we" "can" "do")
>>> type(name)
<class 'str'
>>>> name = "Jerry Jenny"
>>> name
'Jerry Jenny'
>>> type(name)
<class 'str'>>>>
name = ("Jerry Jack Tom")
>>> name
'Jerry Jack Tom'
>>> type(name)
<class 'str'>
```
###一些性质
####\t \n \t\n
#####\t: \t表示空四个字符，也称缩进，相当于按一下Tab键
```
>>> name = "\tJerry Jenny"
>>> print(name)
Jerry Jenny
>>> name = "Jerry\tJenny"
>>> print(name)
Jerry Jenny
>>> name = "Jer\try Jen\tny"
>>> print(name)
Jer ry Jen ny
```
##### \n : \n表示换行，相当于按一下回车
```
>>> name = "Jerry Jenny\n"
>>> print(name)
Jerry Jenny

>>> name = "Jerry\nJenny"
>>> print(name)
Jerry
Jenny
>>> name = "Jerry\nJenn\ny"
>>> print(name)
Jerry
Jenny

```
##### \t\n: \n\t表示换行加每行空四格
```
>>> name = "\tJerry Jenny\n"
>>> print(name)
Jerry Jenny

>>> name = "\tJerry\nJenny"
>>> print(name)
Jerry
Jenny
>>> name = "\t\nJjerry Jenny"
>>> print(name)

Jjerry Jenny
>>> name = "Jerry Jenny\t\n"
>>> print(name)
Jerry Jenny

```
##### .center(number," ")以number个居中对齐

```
>>> name = "Jerry Tom"
>>> name.center(50)
' Jerry Tom '
>>> name.center(50,"-")
'--------------------Jerry Tom---------------------'
```
##### .count(" ",start,end) 找指定字符串在star到end范围内出现的次数
```
>>> name = "Jenny Jerry"
>>> name.count("J")
2
>>> name.count("J",1,7) # 一个空格占一个下标
1
>>> name.count("J",1,6) # 顾头不顾尾
0
>>> name[6]
'J'
>>> name.count("nn")
1
```
##### .endswith("") 检查字符串最后是不是以指定字符结尾的
```
>>> name = "Jenny Jerry"
>>> name.endwith("rry") # 是.endswith而不是endwith哦
Traceback (most recent call last): File "<stdin>", line 1, in <module>AttributeError: 'str' object has no attribute 'endwith'
>>> name = "Jenny Jerry"
>>> name.endswith("rry")
True
>>> name.endswith(3) # 不支持整型
Traceback (most recent call last): File "<stdin>", line 1, in <module>TypeError: endswith first arg must be str or a tuple of str, not int
>>> name.endswith("3")
False
>>> name.endswith("y Jerry")
True
```
##### .startswith("") 检查字符串湿奴是以指定字符开头的
```
>>> name = "Jenny Jerry"
>>> name.startswith("Je")
True
>>> name.startswith("e")
False
```
##### .find("",start,end),同样是顾头不顾尾，在字符串内存在指定字符则返回第一个出现的下标，不存在则返回-1
```
>>> name = "Jerry Jenny"
>>> name.find("J")
0
>>> name.find("J",1)
6
>>> name.find("J",1,7)
6
>>> name.find("J",1,6)
-1 # 顾头不顾尾检索不到6，故不存在返回-1
>>> name.find("m")
-1
```
##### .format() 格式化打印
```
>>> a = "my name is %s,i am %s years old" %("Jerry",20)
>>> a
'my name is Jerry,i am 20 years old'
>>> a = "my name is %s,i am %d years old" %("Jerry",20)
>>> a'
my name is Jerry,i am 20 years old'
>>> a = "my name is {0},i am {1} years old"
>>> a.format("Jerry",20) # 直接打印出来不用再调用a或者print
'my name is Jerry,i am 20 years old'
>>> a = "my name is {name},i am {age} years old"
>>> a.format(name ="Jerry",age=20)'
my name is Jerry,i am 20 years old'
>>> a = "she is {name},{name} is {age} years old"
>>> a.format(name="Jerry",age=20)
'she is Jerry,Jerry is 20 years old'
```
##### .isdigit() 判断是不是整数
```
>>> name = "Jerry"
>>> name.isdigit()
False
>>> age = "12"
>>> age.isdigit()
True
>>> a = "Jerry,20"
>>> a.isdigit()
False
>>> b="12"
>>> b.isdigit()
True
>>> b = "20"+"2"
>>> b
'202'
>>> b.isdigit()
True
>>> b = "20 12"
>>> b.isdigit()
False
>>> "20".isdigit()
True
>>> "20 1".isdigit()
False
>>> a = "20 1"
>>> a
'20 1'
>>> a = 21
>>> a.isdigit()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
AttributeError: 'int' object has no attribute 'isdigit'
```
##### .capitalize() 首字母大写
```
>>> name = "jerry amy"
>>> name.capitalize()
'Jerry amy'
>>> name = "Jerry amy"
>>> name.capitalize()
'Jerry amy'
```
##### .index("",start,end) 索引找出指定元素的第一个下标
```
>>> name = "Jerry"
>>> name.index("J")
0
>>> name.index("r")
2
>>> name.index("r",3,4)
3
```
##### .casefold() 大写全部变为小写
```
>>> name = "Jerry Tom"
>>> name'Jerry Tom'
>>> name.casefold()
'jerry tom'
```
##### .lower()全部变小写
```
>>> name ="Jerry Jenny"
>>> name.lower()
'jerry jenny'
>>> name = "jerry jenny"
>>> name.lower()
'jerry jenny'
```
##### .upper()全部变大写
```
>>> name = "Jenny Jerry"
>>> name.upper()
'JENNY JERRY'
>>> name = "Jenny-Jerry"
>>> name.upper()
'JENNY-JERRY'
```
##### .islower()判断出现字符的地方是不是全都是小写，如果没有字符，比如数字或特殊形式也返回False
```
>>> name ="Jerry Jenny"
>>> name.islower()
False
>>> name = "jerry jenny"
>>> name.islower()
True
>>> name = "13 jerry"
>>> name.islower()
True
>>> age = "20 12"
>>> age.islower()
False
>>> sign = "* & $"
>>> sign.islower()
False
```
##### .isupper()判断出现字符的地方是不是全都是大写，如果没有字符，比如数字或特殊形式也返回False
```
>>> name = "Jerry Jenny"
>>> name.isupper()
False
>>> name = "JERRY JENNY"
>>> name.isupper()
True
>>> name = "12"
>>> name.isupper()
False
>>> name = "JERRY 12"
>>> name.isupper()
True
>>> name = "JENNY 12t"
>>> name.isupper()
False
>>> poems = "曾经沧海难为水，除去巫山不是云"
>>> name.isupper()
False
>>> poems = "曾经沧海难为水，除去巫山不是云A"
>>> poems.isupper()
True
>>> poems = "曾经沧海难为水，除去巫山不是云,A"
>>> poems.isupper()
True
```
##### .swapcase()把字符串里的大写变小写，小写变大写
```
>>> name = "Jenny Jerry"
>>> name.swapcase()
'jENNY jERRY'
>>> poems = "曾经沧海难为水，除去巫山不是云"
>>> poems.swapcase()
'曾经沧海难为水，除去巫山不是云'
```
##### .isspace()判断有没有空间
```
>>> a =''
>>> a.isspace() # 仅有引号不算必须只有空格
False
>>> a = ' '
>>> a.isspace()
True
>>> a = ' '
>>> a.isspace()
True>
>> a = '1 2 3'
>>> a
'1 2 3'
>>> a.isspace()
False
```
##### "".join()把列表或者字符串里面的字符以“”里面的形式拼接起来
```
>>> numbers = [1,2,4]
>>> "-".join(numbers)
Traceback (most recent call last): File "<stdin>", line 1, in <module>TypeError: sequence item 0: expected str instance, int found
>>> str = ["1","2","4"]
>>> "-".join(str)'
1-2-4'
>>> name = ("Jerry" "Jenny" "Alex")
>>> "*".join(name)
'J*e*r*r*y*J*e*n*n*y*A*l*e*x'
>>> "-".join(name)
'J-e-r-r-y-J-e-n-n-y-A-l-e-x'
>>> "".join(name)'
JerryJennyAlex'
>>> name = ("Jerry","Jenny","Alex")
>>> "-".join(name)
'Jerry-Jenny-Alex'
```
##### .ljust(step,"sign") 从左对齐step个不够的用sign补齐
```
>>> poems = ("曾经沧海难为水" "除去巫山不是云")
>>> (poems).ljust(50,"_")
'曾经沧海难为水除去巫山不是云____________________________________'
>>> poems.ljust(50,"-")
'曾经沧海难为水除去巫山不是云------------------------------------'
```
##### .rjust(step,"sign")从右对齐step个不够的用sign补齐
```
>>> poems.rjust(50,"*")
'************************************曾经沧海难为水除去巫山不是云'>>> poems.rjust(50,"")
Traceback (most recent call last): File "<stdin>", line 1, in <module>TypeError: The fill character must be exactly one character long
>>> poems.rjust(50," ")
' 曾经沧海难为水除去巫山不是云'
```
##### .zfill(step)从左对齐step个不够的用0补齐
```
>>> poems = "曾经沧海难为水，除去巫山不是云"
>>> poems.zfill(50)
'00000000000000000000000000000000000曾经沧海难为水，除去巫山不是云'
```
##### .strip() 清楚两边格式即将字符串里两边的换行缩进都清除如果在中间就清除不了
```
>>> name = "Jerry Jenny\t\n"
>>> print(name)
Jerry Jenny

>>> name.strip()
'Jerry Jenny'
>>> name = "Jenny\tJerry\n"
>>> print(name)
Jenny Jerry

>>> name.strip()
'Jenny\tJerry'
>>> name = " Jerry-Jenny \t Jack\n"
>>> print(name)
Jerry-Jenny Jack

>>> name.strip()
'Jerry-Jenny \t Jack'
>>> name = "------------- Jerry\nJenny "
>>> print(name)
------------- JerryJenny
>>> name.strip()
'------------- Jerry\nJenny'
```
##### .lstrip() 清楚左边格式即将字符串左边的换行缩进都清除如果在中间和右边就清除不了
```
>>> name = "\t\nJjerry Jenny"
>>> print(name)

Jjerry Jenny
>>> name.lstrip()
'Jjerry Jenny'
>>> name = "Jerry Jenny\t\n"
>>> name.lstrip()
'Jerry Jenny\t\n'
```
##### .rstrip() 清楚右边格式即将字符串右边的换行缩进都清除如果在中间和左边就清除不了
```
>>> name = "Jerry Jenny\t\n"
>>> name.rstrip()
'Jerry Jenny'
>>> name = "\t\nJjerry Jenny"
>>> name.rstrip()
'\t\nJjerry Jenny'
```
##### .replace("str1","str2",count)把字符串里的str1改count次str2
```
>>> a = "I am 20 years old,and Amy is 20 years old too"
>>> a.replace("20","21")
'I am 21 years old,and Amy is 21 years old too'
>>> a.replace("20","21",1)
'I am 21 years old,and Amy is 20 years old too'
```
##### .split("",count) 通过指定分隔符对字符串进行切片，count默认=-1，即全分
```
>>> name = "Jerry Jenny Jack"
>>> name.split()
['Jerry', 'Jenny', 'Jack'] # 默认count=-1,即全分
>>> name.split(" ",1)
['Jerry', 'Jenny Jack']
>>> name = "Jerry,Jenny,Jack"
>>> name.split()
['Jerry,Jenny,Jack']
>>> name.split(",",1) # 只分一次，从左算起
['Jerry', 'Jenny,Jack']
>>> name = "Jerry-Jenny#Jack"
>>> name
'Jerry-Jenny#Jack'
>>> name.split()
['Jerry-Jenny#Jack']
>>> name.split("-") # 依据-开始分
['Jerry', 'Jenny#Jack']
>>> name.split("#",2)
['Jerry-Jenny', 'Jack']
```
##### .rsplit("",count)和.split()用法基本一样，只是从右开始分，count=-1时看不出来区别
```
>>> name = "Jerry-Jenny#Jack"
>>> name
'Jerry-Jenny#Jack'
>>> name.rsplit()
['Jerry-Jenny#Jack']
>>> name.rsplit("-")
['Jerry', 'Jenny#Jack']
>>> name.rsplit("#")
['Jerry-Jenny', 'Jack']
>>> name = "*Jack*Jerry#Jenny"
>>> name.rsplit("*",1) # 从右开始按*分一次
['*Jack', 'Jerry#Jenny']
>>> name.rsplit("*") # 从右开始按*全分，从又开始算起相当于第一个*号前面是个空格
['', 'Jack', 'Jerry#Jenny']
>>> name.split("*",1) # 从左开始按*分一次
['', 'Jack*Jerry#Jenny']
>>> name.split("*")
['', 'Jack', 'Jerry#Jenny']
```
#### 拼接：可进行字符串的加，乘，例如：
```
str1="一重山"
str2="两重山"
str1+str2
'一重山两重山' # 输出结果
str1*3'一重山一重山一重山' # 输出结果
```
#### 其他运算基本上都不能实现，比如减法，除法，乘方

欧克，先写到这里啦，如果有不对的地方，望指正呀~

wuwuwu好像不支持Markdown，看起来有点乱，可以参看我的CSDN：https://blog.csdn.net/m0_46252978/article/details/105568531

或者简书：https://www.jianshu.com/p/90280e7f8ab7

巴特西

Python中关于字符串你应该知道这些...

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