Problem

Given a string, write a Python function to check if the string is a pangram or not.
Pangrams are words or sentences containing every letter of the alphabet at least once.
Example input: "The quick brown fox jumps over the lazy dog"
Example output: True

Solution

# Solution:

def is_pangram(sentence):
    alphabet = "abcdefghijklmnopqrstuvwxyz"
    for letter in alphabet:
        if letter not in sentence.lower():
            return False
    return True

# Explanation:

# The solution above is optimal because it uses a single loop to check if every letter of the alphabet is in the sentence.
# The alphabet string is created outside of the loop to avoid creating it every time the loop runs.
# The loop checks if each letter is in the sentence, and if it is not, it returns False.
# If the loop finishes without returning False, it returns True.