python字符串find

String.find()方法 (String.find() Method)

find() is an inbuilt method of python, it is used to check whether a sub-string exists in the string or not. If sub-string exists, the method returns the lowest index of the sub-string, if sub-string does not exist, method return -1.

find()是python的内置方法，用于检查字符串中是否存在子字符串。 如果存在子字符串，则该方法返回子字符串的最低索引，如果子字符串不存在，则方法返回-1。

Note: This method is case sensitive.

注意：此方法区分大小写。

Syntax:

句法：

 String.find(sub_string[, start_index[, end_index]])

Parameters:

参数：

• sub_string - a part of the string to be found in the string.

  sub_string-要在字符串中找到的字符串的一部分。

• start_index - an optional parameter, it defines the starting index from where sub_string should be found.

  start_index-可选参数，它定义从中应找到sub_string的起始索引。

• end_index - an optional parameter, it defines end index of the string. Find method will find the sub_string till this end_index.

  end_index-可选参数，它定义字符串的结束索引。 Find方法将查找sub_string直到此end_index 。

Return value:

返回值：

• Returns the lowest index of the sub_string, if it exits in the string.

  返回 sub_string 的最低索引 ，如果它存在于字符串中。

• Returns -1 if sub_string does not exist in the string.

  如果sub_string在字符串中不存在，则返回-1 。

Example:

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))

Output

输出量

    13
13
13
-1
-1

翻译自: https://www.includehelp.com/python/string-find-method-with-example.aspx

python字符串find