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Python Program to Print an Alphabet Pattern

Beginner · Patterns · CBSE class 11 practical list

This program prints a right-angled triangle of capital letters: A on the first row, AB on the second, ABC on the third, and so on. It uses the fact that every character has a number code, so letters can be produced in a loop.

Program

alphabet_pattern.py
rows = 5 # or: rows = int(input("Enter the number of rows: "))
for i in range(1, rows + 1):
for j in range(i):
# chr(65) is "A", chr(66) is "B", and so on
print(chr(65 + j), end="")
print() # move to the next line
Output
A
AB
ABC
ABCD
ABCDE

How it works

  1. chr() turns a character code into a character: chr(65) is "A", chr(66) is "B", and so on up to chr(90), which is "Z".
  2. The outer loop picks the row, and the inner loop prints i letters on it, starting from A each time.
  3. end="" keeps the letters of a row together, and the empty print() starts the next row.
  4. The opposite of chr() is ord(), which gives the code of a character, so ord("A") is 65.

Other ways to write it

Inverted alphabet triangle

Inverted alphabet triangle
rows = 5
for i in range(rows, 0, -1):
for j in range(i):
print(chr(65 + j), end="")
print()
Output
ABCDE
ABCD
ABC
AB
A

Counting the rows down from 5 prints ABCDE first and ends with a single A.

Same letter on each row

Same letter on each row
rows = 5
for i in range(rows):
letter = chr(65 + i)
print(letter * (i + 1))
Output
A
BB
CCC
DDDD
EEEEE

letter * (i + 1) repeats one letter, giving A, BB, CCC, DDDD and EEEEE.

Try it yourself

Change 65 to 97 to print the same pattern in small letters.

Edit the program above and press Run, or open it in the full editor to save it and share it. To watch it run line by line, open it in the visualizer.

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