Python find()

Code-10

Python find() method

description

The Python find() method detects whether the string contains the substring str. If you specify the range of beg (start) and end (end) , then check whether it is included in the specified range , if it contains the substring, return the starting index value, otherwise Returns -1.

grammar

Find() method syntax:

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

parameter

• str-specifies the string to be retrieved
• beg-start index, default is 0.
• end-end index, the default is the length of the string.

return value

If it contains a substring, return the starting index value, otherwise return -1.

Instance

The following example shows an example of the find() method:

#!/usr/bin/python
 
str1 = "this is string example....wow!!!"
str2 = "exam"
 
print(str1.find(str2))
print(str1.find(str2, 10))
print(str1.find(str2, 40))

The output of the above example is as follows:

15
15
-1

str1 = "Life this is string example....wow!!! Python"

start_position = str1.find('this')
end_position = str1.find('wow!!!') + len('wow!!!') # 求出特定字符串的的长度
print(start_position, end_position)
print(str1[start_position: end_position])

# 输出结果
5 37
this is string example....wow!!!

import re

str1 = "Life this is string example....wow!!! Python"
patteren = 'this.*?wow!!!'
layout_re = re.compile(patteren)
result = re.search(layout_re, str1)
print(result)
print(result.group())

# 输出结果：
<re.Match object; span=(5, 37), match='this is string example....wow!!!'>
this is string example....wow!!!

>>>info = 'abca'
>>> print(info.find('a'))    # 从下标0开始，查找在字符串里第一个出现的子串，返回结果：0
0
>>> print(info.find('a',1))  # 从下标1开始，查找在字符串里第一个出现的子串：返回结果3
3
>>> print(info.find('3'))    # 查找不到返回-1
-1
>>>