Python program to check a sentence is a pangrams or not.

A pangram is a sentence that contains every letter of the alphabet at least once. For example, "The quick brown fox jumps over the lazy dog" is a famous pangram. We can check if a sentence is a pangram using Python's set() operations.

Example Input and Output

Input: string = 'abc def ghi jkl mno pqr stu vwx yz'
Output: Yes
// contains all the characters from 'a' to 'z'

Input: string = 'python program'
Output: No
// Does not contain all the characters from 'a' to 'z'

Algorithm

Here's the step-by-step approach to check if a sentence is a pangram:

Step 1: Convert the input string to lowercase
Step 2: Extract only alphabetic characters from the string
Step 3: Convert the alphabetic characters to a set to get unique letters
Step 4: Check if the set contains all 26 letters of the alphabet
Step 5: Return True if all letters are present, False otherwise

Using Set Operations

The most efficient approach uses Python's set operations to compare alphabetic characters ?

def checkPangram(sentence):
    # Convert to lowercase and create set of alphabetic characters
    alphabet_set = set(char.lower() for char in sentence if char.isalpha())
    
    # Check if all 26 letters are present
    return len(alphabet_set) == 26

# Test with example sentences
sentence1 = "The quick brown fox jumps over the lazy dog"
sentence2 = "python program"

print(f'"{sentence1}" is a pangram: {checkPangram(sentence1)}')
print(f'"{sentence2}" is a pangram: {checkPangram(sentence2)}')

"The quick brown fox jumps over the lazy dog" is a pangram: True
"python program" is a pangram: False

Using Boolean Array Method

Another approach uses a boolean array to track which letters are present ?

def checkPangramArray(sentence):
    # Create boolean array for 26 letters
    present = [False] * 26
    
    # Mark letters as present
    for char in sentence.lower():
        if char.isalpha():
            index = ord(char) - ord('a')
            present[index] = True
    
    # Check if all letters are present
    return all(present)

# Test the function
test_sentence = "Pack my box with five dozen liquor jugs"
print(f'"{test_sentence}" is a pangram: {checkPangramArray(test_sentence)}')

"Pack my box with five dozen liquor jugs" is a pangram: True

Interactive Pangram Checker

Here's a complete program that takes user input and checks for pangrams ?

def checkPangram(sentence):
    alphabet_set = set(char.lower() for char in sentence if char.isalpha())
    return len(alphabet_set) == 26

def findMissingLetters(sentence):
    alphabet_set = set(char.lower() for char in sentence if char.isalpha())
    all_letters = set('abcdefghijklmnopqrstuvwxyz')
    return sorted(all_letters - alphabet_set)

# Test with different sentences
sentences = [
    "The quick brown fox jumps over the lazy dog",
    "python programming",
    "Pack my box with five dozen liquor jugs"
]

for sentence in sentences:
    is_pangram = checkPangram(sentence)
    print(f'"{sentence}"')
    
    if is_pangram:
        print("? This is a pangram!")
    else:
        missing = findMissingLetters(sentence)
        print(f"? Not a pangram. Missing letters: {', '.join(missing)}")
    print()

"The quick brown fox jumps over the lazy dog"
? This is a pangram!

"python programming"
? Not a pangram. Missing letters: a, b, c, d, e, f, h, j, k, l, q, s, u, v, w, x, z

"Pack my box with five dozen liquor jugs"
? This is a pangram!

Comparison

Conclusion

Use the set operations method for checking pangrams as it's more concise and readable. Both approaches have O(n) time complexity and efficiently determine if a sentence contains all 26 letters of the alphabet.