这篇文章给大家分享的是有关Python中字符串如何查找的内容。小编觉得挺实用的，因此分享给大家做个参考。一起跟随小编过来看看吧。
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))
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。
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