python之字符串函数

1.  endswith()  startswith()

 # 以什么什么结尾
 # 以什么什么开始
 test = "alex"
 v = test.endswith('ex')
 v = test.startswith('ex')
 print(v)

2. expandtabs()

 test = "1\t2345678\t9"
 v = test.expandtabs(6)
 print(v,len(v))

3. find()

 # 从开始往后找，找到第一个之后，获取其未知
 # > 或 >=
 test = "alexalex"
 # 未找到 -1
 v = test.find('e')
 print(v)

4.  index()

 # index找不到，报错   忽略
 test = "alexalex"
 v = test.index('a')
 print(v)

5. format()  format_map()

 # 格式化，将一个字符串中的占位符替换为指定的值
 test = 'i am {name}, age {a}'
 print(test)
 v = test.format(name='alex',a=19)
 print(v)

 test = 'i am {0}, age {1}'
 print(test)
 v = test.format('alex',19)
 print(v)

 # 格式化，传入的值 {"name": 'alex', "a": 19}
 test = 'i am {name}, age {a}'
 v1 = test.format(name='df',a=10)
 print(v1)
 v2 = test.format_map({"name": 'alex', "a": 19})
 print(v2)

6. isalnum()

 # 字符串中是否只包含 字母和数字
 test = "er;"
 v = test.isalnum()
 print(v)

7.capitalize() 首字母大写

 test = "sqy"
 v = test.capitalize()
 print(v)

8. casefold()  lower() 所有变小写，casefold更牛逼，很多未知的对相应变小写

 test = "sqy"
 v1 = test.casefold()
 print(v1)
 v2 = test.lower()
 print(v2)

9. center() 置宽度，并将内容居中

 # 20 代指总长度
 # *  空白未知填充，一个字符，可有可无
 test = "sqy"
 v = test.center(20,"中")
 print(v)

10.  ljust() rjust() zfill()

 # test = "alex"
 # v = test.ljust(20,"*")
 # print(v)

 # test = "alex"
 # v = test.rjust(20,"*")
 # print(v)

 # test = "alex"
 # v = test.zfill(20)
 # print(v)

11. count() 去字符串中寻找，寻找子序列的出现次数

 test = "aLexalexr"
 v = test.count('ex')
 print(v)

 test = "aLexalexr"
 v = test.count('ex',5,6)
 print(v)

12. isalpha() 是否是字母，汉子

 test = "as大多数df"
 v = test.isalpha()
 print(v)

13. isdecimal()  isdigit() isnumeric()  当前输入是否是数字

 test = "②" # 1，②,儿
 v1 = test.isdecimal()
 v2 = test.isdigit()
 v3 = test.isnumeric()
 print(v1,v2,v3)

14.isprintable() 是否存在不可显示的字符

 # \t   制表符
 # \n   换行
 test = "gdds\tfdsfd"
 v = test.isprintable()
 print(v)

15. isspace()  判断是否全部是空格

 test = "  ass"
 v = test.isspace()
 print(v)

16.  istitle() title() 判断是否是标题

 test = "Return True if all cased characters in S are uppercase and there is"
 v1 = test.istitle()
 print(v1)
 v2 = test.title()
 print(v2)
 v3 = v2.istitle()
 print(v3)

17. join() 将字符串中的每一个元素按照指定分隔符进行拼接

 test = "你是风儿我是沙"
 print(test)
 t = ' '
 v = "_".join(test)
 print(v)

18.  islower() lower()  isupper() upper()

 test = "Alex"
 v1 = test.islower()
 v2 = test.lower()
 print(v1, v2)

 v1 = test.isupper()
 v2 = test.upper()
 print(v1,v2)

19. lstrip()  rstrip() strip()  移除指定字符串 有限最多匹配

 test = "\nxas12xa\n\txax1221axa  "
 v = test.lstrip('xa')
 v = test.rstrip('9lexxexa')
 v = test.strip('xa')
 print(v)

 test.lstrip()
 test.rstrip()
 test.strip()
 # 去除左右空白
 v = test.lstrip()
 v = test.rstrip()
 v = test.strip()
 print(v)
 print(test)
 # 去除\t \n
 v = test.lstrip()
 v = test.rstrip()
 v = test.strip()
 print(v)

20. maketrans()  translate()  对应关系替换

 v = "asidufkasd;fiuadkf;adfkjalsdjf"
 m = str.maketrans("aeiou", "12345")
 new_v = v.translate(m)
 print(new_v)

21. partition()  rpartition() 分割为三部分

 test = "testasdsddfg"
 v = test.partition('s')
 print(v)
 v = test.rpartition('s')
 print(v)

22. split() rsplit()  splitlines()

 test = "sqys"
 v = test.split('s',2)
 print(v)
 v = test.rsplit()
 print(v)

 # 23 分割，只能根据，true，false：是否保留换行
 # test = "asdfadfasdf\nasdfasdf\nadfasdf"
 # v = test.splitlines(False)
 # print(v)

23. swapcase() 大小写转换

 test = "aLex"
 v = test.swapcase()
 print(v)

24. isidentifier() 字母，数字，下划线 ： 标识符 def class

 a = "de12_f"
 v = a.isidentifier()
 print(v)

25.replace()  将指定字符串替换为指定字符串

 test = "alexalexalex"
 v = test.replace("ex",'bbb')
 print(v)
 v = test.replace("ex",'bbb',2)
 print(v)

26.灰魔法

　　一、for循环　　　

 test = "返回到合肥东方红刚才修改"
 # for 变量名 in 字符串:
 #     变量名
 # break
 # continue

 index = 0
 while index < len(test):
     v = test[index]
     print(v)

     index += 1
 print('=======')

 for zjw in test:
     print(zjw)

 test = "好方法个地方个地方刚发的"
 for item in test:
     print(item)
     break

 for item in test:
     continue
     print(item)

　　二、索引，下标，获取字符串中的某一个字符

 test = "好方法个地方个地方刚发的"
 v = test[3]
 print(v)

　　三、切片

 test = "好方法个地方个地方刚发的"
 v = test[0:10] # 0=<  <1
 print(v)

　　四、获取长度

 # Python3： len获取当前字符串中由几个字符组成
 test = "好方法个地方个地方刚发的"
 v = len(test)
 print(v)

27. range()　　获取连续或不连续的数字

 # Python2中直接创建在内容中
 # python3中只有for循环时，才一个一个创建
 v = range(10)
 v = range(3,10)
 v = range(1,10,2)
 # 帮助创建连续的数字,通过设置步长来指定不连续
 v = range(0, 100, 5)

 for item in v:
     print(item)

28.zip()

 # print(list(zip(('a','n','c'),(1,2,3))))
 # print(list(zip(('a','n','c'),(1,2,3,4))))
 # print(list(zip(('a','n','c','d'),(1,2,3))))
 #
 # p={'name':'alex','age':18,'gender':'none'}
 # print(list(zip(p.keys(),p.values())))
 # print(list(p.keys()))
 # print(list(p.values()))
 #
 print(list(zip(['a','b','c'],'')))