python字符串操作增、删、改、查、截取

• 记录python中字符串的操作，以后有了其他的操作会在这个文件中追加

1. 主函数
2. 字符串相加
3. N个字符串相加
4. 字符串替换
5. 循环读取字符串
6. 字符串截取
7. 字符串查找

• 以下所以函数调用的main函数，结果都是基于主函数中的字符串得出的

    if __name__ == "__main__":
        str1 = "Yuang"
        str2 = "PangZi"
        str3 = "YuangPangZi"
        str_list = [str1, str2, str3]
        StrAdd(str1, str2)
        StrSub(str3, str1)
        StrAddList(str_list)
        LoopRead(str1)
        StrSplit(str3)
        FindStr(str3, str1)
        FindStr2(str3, str1)
  

• 字符串相加

  def StrAdd(str1:str, str2:str):  #指定参数的数据类型
      res = str1 + str2
      print("StrAdd: ",res)
      return res
  

  StrAdd:  YuangPangZi
  

• N个字符串相加

  def StrAddList(*args):
  res = ""
  for s in args[0]:
      if isinstance(s, str):
          res += s
  print("StrAddList: ", res)
  return res
  

  StrAddList:  YuangPangZiYuangPangZi
  

• 字符串替换

  def StrSub(source:str, str1:str): 
      res = source.replace(str1, "") #说是减法实则替换
      print("StrSub: ", res)
      return res
  

  StrSub:  PangZi
  

• 循环读取字符串

  def LoopRead(source:str):
      for i in source:
          print("Loop Str: ", i)
  

  Loop Str:  Y
  Loop Str:  u
  Loop Str:  a
  Loop Str:  n
  Loop Str:  g
  

• 字符串截取

  def StrSplit(source:str):
      print("get one char:", source[0], source[1]) #取字符串指定内容1：
      print("get sting in range:",  source[0:2]) #左闭右开 取字符串的指定范围
      print("get char in range for behand:", source[-3: -1]) #从后往前数截取
      print("get one char:", source[-1], source[-2])
  

  get one char: Y u
  get sting in range: Yu
  get char in range for behand: gZ
  get one char: i Z
  

• 字符串查找

  #在source中查找tag是否存在
  def FindStr(source:str, tag:str):
      if tag in source:
          print("True")
          return True
      else:
          print("False")
          return False
  

  True
  

  import re
  #在source中查找tag并获取数量
  def FindStr2(source:str, tag:str):
      res = re.findall(tag, source)
      print("res:", res)
      print("res len", len(res))
  

  res: ['Yuang']
  res len 1
  

s = re.findall(tag, source)
print(“res:”, res)
print(“res len”, len(res))

```shell
res: ['Yuang']
res len 1