A filled diamond star pattern is a centered solid diamond: an upper pyramid of odd-length star rows, mirrored below, with the widest row printed only once.
Remember
Rule: spaces = rows - i, stars = 2 * i - 1
Grow i to rows, then shrink from rows - 1
*
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*****
*******
*********
*******
*****
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* ← rows = 5 (half-height)
In Python you print each row with two inner loops (spaces, then stars), then bare print(). Run that once upward and once downward so the shape closes into a diamond.
Approach
How to Solve It
Reuse one row formula for both halves — start with nested loops, then optionally shorten with string multiplication.
Method
Idea
Best for
Nested loops
Spaces loop + stars loop, twice (up then down)
Learning, interviews, exams
" " * n / "*" * n
Build spaces and stars as whole strings
Shorter demos once loops click
Pseudocode
Pseudocode
for i from 1 to rows: // upper half
print (rows - i) spaces
print (2 * i - 1) stars
print newline
for i from rows - 1 down to 1: // lower half
print (rows - i) spaces
print (2 * i - 1) stars
print newline
Cheat sheet
Goal
Pattern
Upper half
for i in range(1, rows + 1):
Leading spaces
for j in range(rows - i): print(" ", end="")
Odd star run
for k in range(2 * i - 1): print("*", end="")
Lower half
for i in range(rows - 1, 0, -1):
Total lines
2 * rows - 1
Row shortcut
print(" " * (rows - i) + "*" * (2 * i - 1))
Write vs WriteLine
API
Effect
Use for
print(..., end="")
Stays on the same line
Each space and each *
print()
Ends the current line
After spaces and stars for that row
Same idea as C# Write / WriteLine: print characters without a newline, then end the row once.
Try it
Live Preview
Change the half-height and the diamond updates instantly — including line and star totals.
Whole numbers from 1 to 12. Printed lines = 2 * rows - 1.
Live result5 half-height · 9 lines · 41 stars
*
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*****
*******
*********
*******
*****
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*
Trace
Worked Walkthrough — rows = 4
Trace spaces and stars for each i. Upper grows to the middle; lower shrinks from rows - 1.
Three complete programs: fixed half-height, input(), and a string-multiply helper. Use View Output to reveal sample results.
Example 1 — Fixed rows = 5
Hard-coded half-height — ideal for first demos and screenshots.
Python
rows = 5
for i in range(1, rows + 1):
for j in range(rows - i):
print(" ", end="")
for k in range(2 * i - 1):
print("*", end="")
print()
for i in range(rows - 1, 0, -1):
for j in range(rows - i):
print(" ", end="")
for k in range(2 * i - 1):
print("*", end="")
print()
Output
*
***
*****
*******
*********
*******
*****
***
*
How It Works
1. Set half-height.rows = 5 means the diamond peaks at 5 stars wide on each side of center — 9 total lines.
2. Upper half.i runs from 1 to rows. Print rows - i spaces, then 2 * i - 1 stars, then a newline.
3. Lower half.i runs from rows - 1 down to 1 with the same two inner loops — so the widest row is not repeated.
4. Break the line. Bare print() after both inner loops starts the next row.
Example 2 — User Input Version
Read the half-height at runtime. Prefer a try / except in real apps (shown in the tip below).
Python
rows = int(input("Enter the number of rows: "))
for i in range(1, rows + 1):
for j in range(rows - i):
print(" ", end="")
for k in range(2 * i - 1):
print("*", end="")
print()
for i in range(rows - 1, 0, -1):
for j in range(rows - i):
print(" ", end="")
for k in range(2 * i - 1):
print("*", end="")
print()
Output (when user enters 4)
Enter the number of rows: 4
*
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*****
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*****
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*
How It Works
1. Prompt and read.input() returns a string; int(...) converts it to a whole number.
2. Same two-phase core. Only the source of rows changes — the print logic matches Example 1.
3. Safer input tip.int(input()) raises ValueError on letters. Prefer:
Safer input
raw = input("Enter the number of rows: ").strip()
try:
rows = int(raw)
except ValueError:
print("Enter a positive whole number.")
raise SystemExit
if rows < 1:
print("Enter a positive whole number.")
raise SystemExit
Example 3 — String Multiply Helper
Build each row in one call — same shape, no explicit space/star inner loops.
Python
def print_row(rows, i):
print(" " * (rows - i) + "*" * (2 * i - 1))
rows = 5
for i in range(1, rows + 1):
print_row(rows, i)
for i in range(rows - 1, 0, -1):
print_row(rows, i)
Output
*
***
*****
*******
*********
*******
*****
***
*
How It Works
1. One helper for a row.print_row builds rows - i spaces and 2 * i - 1 stars, then prints the line.
2. Same outer structure. Call it upward for i = 1..rows, then downward from rows - 1.
3. Learn loops first. Use Examples 1–2 when you need to show nested bounds; treat this as a polish shortcut afterward.
Edge Cases & Pitfalls
Check these before calling the solution done.
Lower at rows
Doubled middle
If the lower loop starts at rows, the widest line prints twice. Start at rows - 1.
Even stars
Lost center
Use 2 * i - 1 (odd counts). Even widths break left–right symmetry.
Wrong spaces
Not centered
Spaces must be rows - i. Using i spaces leans the diamond the wrong way.
rows = 1
Single star
Upper prints *; lower never runs — correct tiny diamond.
rows ≤ 0
Empty output
Both outer loops skip. Validate and re-prompt for interactive programs.
Bad input
Catch ValueError
int(input()) throws on letters — prefer try / except ValueError.
Analysis
Time and Space Complexity
Program
Time
Extra space
Nested loops (Examples 1–2)
O(rows²)
O(1)
String multiply helper (Example 3)
O(rows²)
O(rows) per temporary row string
About 2 * rows - 1 lines; each line does Θ(rows) work for spaces and stars. Total stars = rows² + (rows - 1)².
Remember
Key Takeaways
Row formula:rows - i spaces and 2 * i - 1 stars.
Two phases: grow i to rows, then shrink from rows - 1.
Break the row:print(..., end="") for spaces/stars; bare print() after both inner loops.
Complexity:O(n²) time for half-height n; O(1) extra space for nested loops.
One line: spaces = rows - i, stars = 2*i - 1, grow then shrink from rows - 1.
Frequently Asked Questions
The first outer loop runs i from 1 to rows. On each row it prints (rows - i) spaces, then (2 * i - 1) stars. That builds the upper centered pyramid. The second outer loop runs i from (rows - 1) down to 1 with the same two inner loops, mirroring the shape so the diamond closes.
The first part already prints the widest row when i equals rows. Starting the second part at rows - 1 continues with the next narrower rows without repeating the middle line.
The filled diamond prints full runs of stars using 2*i-1 stars per row. The hollow diamond uses diagonal conditions so only the outline has stars. Both use an upper phase and a lower phase starting at rows - 1.
Odd widths keep a single center star on each row and grow by one star on each side per step, which keeps left–right symmetry.
print(" ", end="") or print("*", end="") stays on the same line. print() ends the current line. Spaces and stars use end=""; the row break uses print() after both inner loops.
With n equal to rows (half-height), there are 2n - 1 printed lines. Each line does Theta(n) work for spaces and stars combined, so overall time is O(n²).
Exactly 2 * rows - 1 lines. The widest line has 2 * rows - 1 stars.
Wrap int(input()) in try/except ValueError and require rows >= 1 so bad input does not crash the script.
🤔
Did you know?
The filled diamond is Program 5’s pyramid plus its mirror: same (rows - i) spaces and (2 * i - 1) stars, with the lower half starting at rows - 1 so the widest row prints only once.
