Python字符串 rfind() 方法

如果在给定的字符串中找到， Python String rfind()方法返回子字符串的最高索引。如果未找到，则返回-1。

Syntax: 

str.rfind(sub, start, end)

Parameters: 

• sub: It’s the substring that needs to be searched in the given string. 
• start: Starting position where the sub needs to be checked within the string. 
• end: Ending position where suffix needs to be checked within the string. 

Note: If start and end indexes are not provided then, by default it takes 0 and length-1 as starting and ending indexes where ending indexes are not included in our search.

Return: 

Returns the highest index of the substring if it is found in the given string; if not found, then it returns -1.

Exception: 

ValueError: This error is raised in the case when the argument string is not found in the target string.

示例 1

Python3

# Python program to demonstrate working of rfind()
# in whole string
word = 'geeks for geeks'
  
# Returns highest index of the substring
result = word.rfind('geeks')
print ("Substring 'geeks' found at index :", result )
  
result = word.rfind('for')
print ("Substring 'for' found at index :", result )
  
word = 'CatBatSatMatGate'
  
# Returns highest index of the substring
result = word.rfind('ate')
print("Substring 'ate' found at index :", result)

输出：

Substring 'geeks' found at index : 10
Substring 'for' found at index : 6
Substring 'ate' found at index : 13

示例 2

Python3

# Python program to demonstrate working of rfind()
# in a sub-string
word = 'geeks for geeks'
  
# Substring is searched in 'eeks for geeks'
print(word.rfind('ge', 2))
  
# Substring is searched in 'eeks for geeks' 
print(word.rfind('geeks', 2))
  
# Substring is searched in 'eeks for geeks' 
print(word.rfind('geeks ', 2))
  
# Substring is searched in 's for g'
print(word.rfind('for ', 4, 11))

输出：

10
10
-1
6

示例 3：实际应用

在字符串检查中很有用。检查给定的子字符串是否存在于某个字符串中。

Python3

# Python program to demonstrate working of rfind()
# to search a string
word = 'CatBatSatMatGate'
  
if (word.rfind('Ate') != -1):
    print ("Contains given substring ")
else:
    print ("Doesn't contains given substring")

输出：

Doesn't contains given substring