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Python Program that Displays the Letters that are in the First String but not in the Second
  • Last Updated : 25 Nov, 2020

Python program to display the letters in the first string but not in the second can be done by taking two sets and subtracting them. As sets support the difference operator, one set could contain the letters of the first string and another set could contain the letters of the second string and when subtracted we could obtain the desired result.

Examples:

Input: set1 = { 'r', 'o', 'h', 'a', 'n'}
       set2 = { 'r', 'i', 't', 'i', 'k', 'a'}
Output: set1 - set2 = { 'o', 'h', 'n'}

Input: a = { 'g', 'e', 'e', 'k', 's', 'f', 'o', 'r'}
       b = { 'g', 'e', 'e', 'k', 's'}
Output: c = a - b = { 'f', 'o', 'r'}

Approach: 

  • Take two string, say, a and b
  • Convert that strings into sets, say, setA and setB
  • Subtract setB from setA
  • Print the result

Below are some examples of the above approach.

Example 1:



Python3




# string 1
a = "geeksforgeeks"
  
# string 2
b = "geeks"
  
# convert string 1 into set
setA = set(a)
  
# convert string 2 into set
setB = set(b)
  
# store the difference in form of list
result = setA-setB
  
# print result
print(result)
Output
{'r', 'f', 'o'}

Example 2:

Python3




# string 1
a = "rohan"
  
# string 2
b = "mohali"
  
# store the difference of sets
result = set(a)-set(b)
  
# print result
print(result)
Output
{'r', 'n'}

Note: The output of the above programs will always be different because sets are unordered collections, thus when subtracted they produce unordered results. 

By the above approach, we could obtain all the letters present in the first string but not in the second.

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