Python中字符串如何查找?

发布时间:2022-05-18 09:45:56 人气:26 作者:多测师

  在Python使用字符串的过程中,如果遇到很多的字符串,想要查找到想要的字符串有些困难。本文主要介绍Python字符串查找的几种方法:find方法、 index方法、rfind方法、rindex方法。具体请看如下内容:

  find方法

  find方法获取值时,如果要查找的值不存在,会返回-1

  str.find(str, beg=0, end=len(string))

Python中字符串如何查找?

  使用实例

  # string in which we have to find the sub_string

  str = "Hello world, how are you?"

  # sub_string to find the given string

  sub_str = "how"

  # find by sub_str

  print (str.find (sub_str))

  # find by sub_str with slice:start index

  print (str.find (sub_str, 10))

  # find by sub_str with slice:start index and slice: end index

  print (str.find (sub_str, 10, 24))

  # find a sub_str that does not exist

  sub_str = "friend"

  # find by sub_str

  print (str.find (sub_str))

  # find a sub_str with different case

  sub_str = "HOW"

  # find by sub_str

  print (str.find (sub_str))

  输出

  13

  13

  13

  -1

  -1

  index方法

  在获取值得索引时,如果不存在值,会报错

  str.index(str, beg=0, end=len(string))

  使用实例

  def second_index(text: str, symbol: str):

  """

  returns the second index of symbol in a given text

  """

  try:

  return text.index(symbol, text.index(symbol) + 1)

  except ValueError:

  return None

  if __name__ == '__main__':

  #These "asserts" using only for self-checking and not necessary for auto-testing

  print('Example:')

  print(second_index("sims", "s"))

  assert second_index("sims", "s") == 3, "First"

  assert second_index("find the river", "e") == 12, "Second"

  assert second_index("hi", " ") is None, "Third"

  assert second_index("hi mayor", " ") is None, "Fourth"

  assert second_index("hi mr Mayor", " ") == 5, "Fifth"

  print('You are awesome! All tests are done! Go Check it!')

  注意:

  find()和index()只能找到第一个索引值。如果指定字符同时存在多个,只会输出第一个指定字符的索引值。

  rfind和rindex方法用法和上面一样,只是从字符串的末尾开始查找。

  以上内容为大家介绍了Python中字符串如何查找?希望对大家有所帮助,如果想要了解更多Python相关知识,请关注多测师。https://www.e70w.com/xwzx/


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