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

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.

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.

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 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.

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)