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• Python find() Method ： Detects whether a string contains a substring

Python find() Method ： Detects whether a string contains a substring

find() Method to retrieve whether a string contains a target string , If you include , The index of the first occurrence of the string is returned ; conversely , Then return to -1.

find() The syntax of the method is as follows ：

str.find(sub[,start[,end]])

The meanings of parameters in this format are as follows ：

• str： Represents the original string ;
• sub： Represents the target string to retrieve ;
• start： Indicates where to start the search . If you don't specify , By default, search from the beginning ;
• end： Indicates the end position of the end Retrieval . If you don't specify , The default is to search until the end .

【 example 1】 use find() Method retrieval “c.biancheng.net” First time in “.” Location index of .

>>> str = "c.biancheng.net"
>>> str.find('.')
1

【 example 2】 Manually specify the location of the starting index .

>>> str = "c.biancheng.net"
>>> str.find('.',2)
11

【 example 3】 Manually specify the location of the start index and end index .

>>> str = "c.biancheng.net"
>>> str.find('.',2,-4)
-1

At index （2,-4） The string between is “biancheng”, Because it does not contain “.”, therefore find() The return value of the method is -1.

Be careful ,Python It also provides rfind() Method , And find() The biggest difference in the method is ,rfind() Is to retrieve from the right side of the string . for example ：

>>> str = "c.biancheng.net"
>>> str.rfind('.')
11