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Python Program to Print a Diamond Pattern

Beginner · Patterns

A diamond pattern is a pyramid with an upside-down pyramid underneath it. With 5 rows in the top half, the rows have 1, 3, 5, 7 and 9 stars, then 7, 5, 3 and 1 again. The bottom half skips the widest row so it is not printed twice.

Program

diamond_pattern.py
rows = 5 # rows in the top half; or: rows = int(input("Enter the number of rows: "))
# Top half: a pyramid with 1, 3, 5, 7, 9 stars
for i in range(1, rows + 1):
spaces = " " * (rows - i)
stars = "*" * (2 * i - 1)
print(spaces + stars)
# Bottom half: the same rows in reverse, starting below the middle row
for i in range(rows - 1, 0, -1):
spaces = " " * (rows - i)
stars = "*" * (2 * i - 1)
print(spaces + stars)
Output
    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

How it works

  1. Both halves use the same rule: row i has rows - i spaces followed by 2 * i - 1 stars.
  2. The first loop counts i up from 1 to rows, which draws a pyramid ending with the widest row of 9 stars.
  3. The second loop counts i down from rows - 1 to 1, which draws the same rows again in reverse.
  4. Starting the second loop at rows - 1 instead of rows stops the widest row from appearing twice.
  5. " " * n and "*" * n repeat a character n times, so each row is built without an inner loop.

Other ways to write it

One loop using abs()

One loop using abs()
rows = 5
for k in range(-(rows - 1), rows): # k runs -4, -3, ..., 3, 4
spaces = abs(k) # 4, 3, 2, 1, 0, 1, 2, 3, 4
stars = 2 * (rows - spaces) - 1 # 1, 3, 5, 7, 9, 7, 5, 3, 1
print(" " * spaces + "*" * stars)
Output
    *
   ***
  *****
 *******
*********
 *******
  *****
   ***
    *

abs(k) is the distance from the middle row, so a single loop from -4 to 4 prints fewer spaces and more stars as it nears the middle, and the reverse after it.

Hollow diamond

Hollow diamond
rows = 5
for k in range(-(rows - 1), rows):
spaces = abs(k)
width = 2 * (rows - spaces) - 1 # how wide this row is
if width == 1:
print(" " * spaces + "*")
else:
print(" " * spaces + "*" + " " * (width - 2) + "*")
Output
    *
   * *
  *   *
 *     *
*       *
 *     *
  *   *
   * *
    *

Only the first and last positions of each row get a star, with width - 2 spaces between them, so just the outline of the diamond is drawn.

Try it yourself

Change rows to 7 and replace the stars with the first letter of your name.

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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