A fill-with-n triangle prints a fixed-width row each time — first the ascending sequence i..n, then pad the rest with n.
Rule: for i = n..1
print i..n, then pad with n (i - 1 times)
5 5 5 5 5
4 5 5 5 5
3 4 5 5 5
2 3 4 5 5
1 2 3 4 5 ← n = 5After Program 18’s odd/even triangle, this pattern teaches two inner loops that keep every row the same width.
Walk i from n down to 1; print the sequence, then pad with n.
| Method | Idea | Best for |
|---|---|---|
| Two inner loops | Sequence i..n; fill i - 1 times with n | Learning, interviews |
| input() width | Same loops; read n at runtime | Interactive practice |
| Custom fill | Same shape; pad with a separate constant | Fill variants |
for i from n down to 1:
for j from i to n:
print j (same line, spaced)
for j from 1 to i - 1:
print n (same line, spaced)
print newline| Goal | Pattern |
|---|---|
| Set width | n = 5 |
| Outer loop | for i in range(n, 0, -1): |
| Sequence | for j in range(i, n + 1): print(j, end=" ") |
| Fill pad | for j in range(1, i): print(n, end=" ") |
| End row | print() |
| Width per row | Always n |
| Custom fill | print(fill, end=" ") in the second loop |
| API | Effect | Use for |
|---|---|---|
print(j, end=" ") | Stays on the same line | Each number |
print() | Ends the current line | After both inner loops |
Print numbers with end=" ", then break once with print(). Putting print() inside an inner loop prints one number per line.
Change n and the fill-with-n triangle updates instantly.
n = 3Trace each outer i, the sequence segment, the fill count, and the printed row.
i | Sequence i..n | Fill count | Printed row |
|---|---|---|---|
3 | 3 | 2 × 3 | 3 3 3 |
2 | 2 3 | 1 × 3 | 2 3 3 |
1 | 1 2 3 | none | 1 2 3 |
Fill count = i - 1. Every row has exactly n values. Total = n².
Three complete programs: fixed n = 5, input() width, and custom fill. Use View Output for sample results.
n = 5Hard-coded width — sequence loop, then pad with n.
n = 5
for i in range(n, 0, -1):
for j in range(i, n + 1):
print(j, end=" ")
for j in range(1, i):
print(n, end=" ")
print()1. Outer loop. i runs from 5 down to 1 — the start of the ascending sequence.
2. Sequence. Print j from i to n.
3. Fill. Print n exactly i - 1 times, then print() ends the row.
Read n at runtime; fill value matches the width.
n = int(input("Enter the triangle width: "))
for i in range(n, 0, -1):
for j in range(i, n + 1):
print(j, end=" ")
for j in range(1, i):
print(n, end=" ")
print()1. Read n. Convert the prompt answer with int().
2. Same shape. Sequence and fill still use the same n — only the source changes.
3. Safer input tip. Bare int(input()) raises ValueError on letters. Prefer:
raw = input("Enter the triangle width: ").strip()
try:
n = int(raw)
except ValueError:
print("Enter a positive whole number.")
raise SystemExit(1)
if n < 1:
print("Enter a positive whole number.")
raise SystemExit(1)Pad with fill = 9 while the sequence still runs up to n = 5.
n = 5
fill = 9
for i in range(n, 0, -1):
for j in range(i, n + 1):
print(j, end=" ")
for j in range(1, i):
print(fill, end=" ")
print()1. Same structure. Outer and both inner loop bounds match Example 1.
2. Only the pad changes. The second loop prints fill instead of n.
3. Sequence unchanged. The ascending i..n part still uses the width n.
Check these before calling the solution done.
Without the second loop, early rows are short. Always pad i - 1 times.
If print() is inside either inner loop, each number lands on its own line.
Using range(1, n + 1) for the outer loop prints the full sequence first. Keep range(n, 0, -1) for this shape.
Fill with range(1, i) — that is i - 1 times. range(1, i + 1) overshoots the width.
Output is just 1 — the fill loop never runs.
Letters crash bare int(input()) — wrap in try/except and require n >= 1.
| Program | Time | Extra space |
|---|---|---|
| Examples 1–3 | O(n²) | O(1) |
Each of n rows prints n values → total n² → O(n²).
i..n, then pad with n for i - 1 slots.n values.print() advances after both loops.n² → O(n²).One line: print the rising tail, then fill the rest of the row with n.
Each row prints an ascending sequence i..n, then pads with n so every row has width n. The second inner loop runs i - 1 times — still O(n²) total prints.
Continue with the next pattern in the Python number-pattern series.
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