Python String Methods – Set 1 (find, rfind, startwith, endwith, islower, isupper, lower, upper, swapcase & title)

Last Updated : 02 Apr, 2025

Some of the string basics have been covered in the below articles:

Strings Part-1
Strings Part-2

The important string methods will be discussed in this article

1. find(“string”, beg, end) :- This function is used to find the position of the substring within a string. It takes three arguments:

substring: The string to search for.
beg (starting index, default = 0).
end (ending index, default = string length).

returns -1 if the substring is not found in the given range.
returns the first occurrence of the substring if found.

2. rfind(“string”, beg, end) :- This function has the similar working as find(), but it returns the position of the last occurrence of string.

Python

str = "geeksforgeeks is for geeks" s = "geeks"  # using find() to find first occurrence of s print ("The first occurrence of s is at : ", end="") print (str.find( s, 4) )  # using rfind() to find last occurrence of s print ("The last occurrence of s is at : ", end="") print ( str.rfind( s, 4) )

Output:

The first occurrence of str2 is at : 8
The last occurrence of str2 is at : 21

Time complexity : O(n)
Auxiliary Space : O(1)

3. startswith(“string”, beg, end) :- The purpose of this function is to return true if the function begins with mentioned string(prefix) else return false.
4. endswith(“string”, beg, end) :- The purpose of this function is to return true if the function ends with mentioned string(suffix) else return false.

Python

str = "geeks" s = "geeksforgeeksportal"  # using startswith() to find if str  # starts with s  if s.startswith(str):          print ("s begins with : " + str)  else : print ("s does not begin with : "+ str)   # using endswith() to find  # if str ends with s  if s.endswith(str):      print ("s ends with : " + str)  else :      print ("s does not end with : " + str)

Output:

str1 begins with : geeks
str1 does not end with : geeks

Time complexity : O(n)
Auxiliary Space : O(1)

5. islower(“string”) :- This function returns true if all the letters in the string are lower cased, otherwise false.
6. isupper(“string”) :- This function returns true if all the letters in the string are upper cased, otherwise false.

Python

# Python code to demonstrate working of  # isupper() and islower() str = "GeeksforGeeks" str1 = "geeks"  # checking if all characters in str are upper cased if str.isupper() :     print ("All characters in str are upper cased") else :      print ("All characters in str are not upper cased")  # checking if all characters in str1 are lower cased if str1.islower() :     print ("All characters in str1 are lower cased") else :      print ("All characters in str1 are not lower cased")

Output:

All characters in str are not upper cased
All characters in str1 are lower cased

Time complexity : O(n)
Auxiliary Space : O(1)

7. lower() :- This function returns the new string with all the letters converted into its lower case.
8. upper() :- This function returns the new string with all the letters converted into its upper case.
9. swapcase() :- This function is used to swap the cases of string i.e upper case is converted to lower case and vice versa.
10. title() :- This function converts the string to its title case i.e the first letter of every word of string is upper cased and else all are lower cased.

Python

str = "GeeksForGeeks is fOr GeeKs"  # Converting string into its lower case s1 = str.lower(); print (" lower case string : " + str1)  # Converting string into its upper case s2 = str.upper(); print (" upper case string : " + str2)  # Converting string into its swapped case s3 = str.swapcase(); print (" swap case string : " + str3)  # Converting string into its title case s4 = str.title(); print (" title case string : " + str4)

Output:

 The lower case converted string is : geeksforgeeks is for geeks
 The upper case converted string is : GEEKSFORGEEKS IS FOR GEEKS
 The swap case converted string is : gEEKSfORgEEKS IS FoR gEEkS
 The title case converted string is : Geeksforgeeks Is For Geeks

Time complexity : O(n)
Auxiliary Space : O(1)