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

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  • Difficulty Level : Easy
  • Last Updated : 16 Jun, 2022
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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 3 arguments, substring , starting index( by default 0) and ending index( by default string length)
 

  • It returns “-1 ” if string is not found in given range.
  • It returns first occurrence of string 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




# Python code to demonstrate working of
# find() and rfind()
str = "geeksforgeeks is for geeks"
str2 = "geeks"
 
# using find() to find first occurrence of str2
# returns 8
print ("The first occurrence of str2 is at : ", end="")
print (str.find( str2, 4) )
 
# using rfind() to find last occurrence of str2
# returns 21
print ("The last occurrence of str2 is at : ", end="")
print ( str.rfind( str2, 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.
 

Python3




# Python code to demonstrate working of
# startswith() and endswith()
str = "geeks"
str1 = "geeksforgeeksportal"
 
# using startswith() to find if str
# starts with str1
if str1.startswith(str):
        print ("str1 begins with : " + str)
else : print ("str1 does not begin with : "+ str)
 
# using endswith() to find
# if str ends with str1
if str1.endswith(str):
    print ("str1 ends with : " + str)
else :
    print ("str1 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.
 

Python3




# 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.
 

Python3




# Python code to demonstrate working of
# upper(), lower(), swapcase() and title()
str = "GeeksForGeeks is fOr GeeKs"
 
# Converting string into its lower case
str1 = str.lower();
print (" The lower case converted string is : " + str1)
 
# Converting string into its upper case
str2 = str.upper();
print (" The upper case converted string is : " + str2)
 
# Converting string into its swapped case
str3 = str.swapcase();
print (" The swap case converted string is : " + str3)
 
# Converting string into its title case
str4 = str.title();
print (" The title case converted string is : " + 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)


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