Python学习-str字符串

1.字符串的格式

1 learn_str = "ZiFuChuan"
2 learn_str = str("ZiFuChuan")

2.字符串的运行原理

1 learn_str = "ZiFuChuan" => "ZiFuChuan" = [‘Z‘,‘i‘,‘F‘,‘u‘...]

3.字符串的内置功能

*索引

1 learn_str = "ZiFuChuan"
2 print(learn_str[0])  =>  "Z"
3 print(learn_str[1])  =>  "i"
4
5 print(learn_str[-1])  =>  "n"
6 print(learn_str[-2])  =>  "a"

*切片

1 learn_str = "ZiFuChuan"
2 print(learn_str[0:3])  =>  "Zi"
3 print(learn_str[:3])  =>  "Zi"
4
5 print(learn_str[-3:0])  =>  无返回
6 print(learn_str[-3:])  =>  ‘uan‘
7 print(learn_str[-3:-1])  =>  "ua"
8 print(learn_str[:-1])  => "ZiFuChua"

* "+" 字符串连接

1 learn_str_1 = ‘wo‘
2 learn_str_2 = ‘ni‘
3 print(learn_str_1 + learn_str_2)  => woni
4 print(‘wo‘ + ‘ni‘) => woni

* "*" 字符串的重复输出

1 learn_str_1 = ‘wo‘
3 print(learn_str_1 * 3)  => wowowo
4 print(‘wo‘ * 3) => wowowo

* capitalize() 第一个字母大写

1 learn_str = "ZiFuChuan"
2 print(learn_str.capitalize())  => Zifuchuan

* lower() 所有大写字母变为小写

1 learn_str = "ZiFuChuan"
2 print(learn_str.lower())  =>  zifuchuan

* upper() 所有小写字母变为大写

1 learn_str = "ZiFuChuan"
2 print(learn_str.upper())  =>  ZIFUCHUAN

* center(width,fillchar=None)  内容居中，空白处可填充

1 learn_str = "ZiFuChuan"
2 print(learn_str.center(20))  => "     ZiFuChuan     " 一共20位
3 print(learn_str.center(20,"*"))  =>  "*****ZiFuChuan*****"

*ljust(width,fillchar=None) 内容左对齐，右侧填充

1 learn_str = "ZiFuChuan"
2 print(learn_str.ljust(20,‘*‘))  =>  ZiFuChuan**********

*rjust(width,fillchar=None) 内容右对齐，左侧填充

1 learn_str = "ZiFuChuan"
2 print(learn_str.rjust(20,‘*‘))  =>  **********ZiFuChuan

*count(sub,strat=None,end=None) 子序列个数

1 learn_str = "ZiFuChuan"
2 print(learn_str.count("u"))  =>  2
3 print(learn_str.count("u",4))  =>  1
4 print(learn_str.count("u",4,6))  => 05 print(learn_str,count("hu")) => 1

*endswith(suffix,start=None,end=None) 是否以子序列结尾

learn_str = "ZiFuChuan"
print(learn_str.endswith(‘n‘))   => True
print(learn_str.endswith(‘an‘))   => True
print(learn_str.endswith(‘i‘,0,2))   => True

* startswth(suffix,start=None,end=None)  是否以子序列开头

1 learn_str = "http://www.w3cschool.cc/"
2 print(learn_str.startswith(‘h‘))  ==》 Thue

*expandtabs(tablesize=None) 将tab转换为空格，默装换为8个空格

learn_str = "ZiFu\tChuan"
print(learn_str.expandtabs()) => "ZiFu        Chuan"
print(learn_str.expandtabs(2)) => "ZiFu  Chuan"

*find(sub,start=None,end=None) 寻找子序列位置，若未找到返回-1

learn_str = "ZiFuChuan"
print(learn_str.find("u"))  => 3
print(learn_str.find(‘iF‘)) => 1
print(learn_str.find(‘g‘)) => -1
print(learn_str.find(‘F‘, 1, 3)) => 2 此处区间位置不会按照所在位置取
print(learn_str.find(‘F‘, 3, 4)) => -1

*rfind(sub,start=None,end=None) 寻找子序列位置，从右边开始，若未找到返回-1

1 learn_str = "ZiFuChuan"
2 print(learn_str.find("u"))  => 6

*index(sub,start=None,end=None) 寻找子序列位置，若未找到报错

1 learn_str = "ZiFuChuan"
2 print(learn_str.index(‘u‘))  => 3
3 print(learn_str.index(‘W‘)) => 报错

*rindex(sub,start=None,end=None) 寻找子序列位置，从右边开始，若未找到报错

1 learn_str = "ZiFuChuan"
2 print(learn_str.rindex(‘u‘))  => 6
3 print(learn_str.rindex(‘W‘)) => 报错

*format() 字符串的格式化

print(‘My {} is {}‘.format(‘haha‘,‘hehe‘)) => My haha is hehe
print(‘My {name} is {names}‘.format(name=‘haha‘,names=‘hehe‘)) => My haha is hehe

*join(iterable) 连接

1 learn_str = (‘a‘,‘b‘,‘c‘,‘d‘,‘e‘)
2 print(‘‘.join(learn_str))  =>  abcde
3 print(‘-‘.join(learn_str))  => a-b-c-d-e

*strip(chars=None) 移除字符串两侧空白或指定序列

1 learn_str = "  ZiFuChuan  "
2 print(learn_str.strip()) => ZiFuChuan
3 learn_str = "**ZiFuChuan**"
4 print(learn_str.srtip(‘*‘)) => ZiFuChuan  

*lstrip(chars=None) 移除字符串左侧空白或指定序列

learn_str = "  ZiFuChuan  "
print(learn_str.lstrip()) => ‘ZiFuChuan  ‘
learn_str = "**ZiFuChuan**"
print(learn_str.lstrip(‘*‘)) => "ZiFuChuan**"

*rstrip(chars=None) 移除字符串右侧空白或指定序列

1 learn_str = "  ZiFuChuan  "
2 print(learn_str.rstrip()) => ‘  ZiFuChuan‘
3 learn_str = "**ZiFuChuan**"
4 print(learn_str.rstrip(‘*‘)) => "**ZiFuChuan"

*partition(sep) 分割前中后三个部分

1 str = "http://www.w3cschool.cc/"
2 print(str.partition(‘://‘))
3 ==> [‘http‘ ‘://‘ ‘www.w3cschool.cc/‘]

*rpartition(sep) 分割前中后三个部分，从右侧检测

1 learn_str = "http://www.w3cschool.cc/"
2 print(learn_str.rpartition(‘w‘))
3 ==> [‘http://www.‘ ‘w‘ ‘3cschool.cc/‘]

*split(str="",num=srting.count(str)) 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

1 learn_str = "http://www.w3cschool.cc/"
2 print(learn_str.split("w"))
3 ==> [‘http://‘, ‘‘, ‘‘, ‘.‘, ‘‘, ‘3cschool.cc/‘]
4 print(learn_str.split("w",2))
5 ==> [‘http://‘, ‘‘, ‘w.w3cschool.cc/‘]

*rsplit(str="",num=srting.count(str)) 从右侧开始检索，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

learn_str = "http://www.w3cschool.cc/"
print(learn_str.rsplit("w"))
 ==》 [‘http://‘, ‘‘, ‘‘, ‘.‘, ‘3cschool.cc/‘]
print(learn_str.rsplit("w",2))
 ==》 [‘http://ww‘, ‘.‘, ‘3cschool.cc/‘]

* replace(old,new,count=None) 替换字符列

1 learn_str = "ZiFuChuan"
2 print(learn_str.replace(‘u‘,‘s‘))    => ZiFsChsan
3 print(learn_str.replace(‘Fu‘,‘s‘))  => ZisChuan
4 print(learn_str.replace(‘u‘,‘s‘,1))  => ZiFsChuan
5 ==>count参数表示替换的个数

* translate(table,deletechars=None) 转换，需要先做一个对应表。

1 intab = ‘aeiou‘
2 outtab = ‘12345‘
3 trantab = str.maketrans(intab, outtab)
4
5 learn_str = ‘this is string example...wow!!!‘
6 print(learn_str.translate(trantab))
7 ==》th3s 3s str3ng 2x1mpl2...w4w!!!

* zfill 返回指定长度的字符串，原字符串右对齐，前面填充0。

1 learn_str = "ZiFuChuan"
2 print(learn_str.zfill(15)) => "000000ZiFuChuan"

* decode() 解码

* encode() 编码针对unicode

* isalnum() 是否是字母和数字，返回布尔值

* isalpha() 是否是字母，返回布尔值

* isalgif() 是否是字母，返回布尔值

* islower() 是否小写，返回布尔值