Adding recursion and converting a for loop into a while loop

Question

This is my code, I am trying to add recursion so when the user inputs a number less than 0, it will not only say Invalid Entry, but it will also bring up the original prompt for them to try another number. I am also trying to change my for loop into a while loop. Any help?

space = '\t'
star = '*'
size = int(input("Enter the height of the pattern (must be greater than 0): "))

if size <= 0 :
    print("Invalid Entry!\n")

for i in range(0, size) :
    star_count = 2 * i - 1

    line = space * (size - i - 1)

    if i == 0 :
        line += "1"
    else :
        line += str(2 * i) + space

    line += (star + space) * star_count

    if i > 0 :
        line += str(2 * i + 1)

    print(line)

The output should look like this

                1
            2   *   3
        4   *   *   *   5
    6   *   *   *   *   *   7
8   *   *   *   *   *   *   *   9

Rather than recursion you may want to check the user input in a loop. The loop will terminate if user provide a value greater than 0 — kuro, May 13 '21 at 05:00
your code never will display the output as you intend to. Partial solution to your query is this change below lines to if size <= 0 : print("Invalid Entry!\n") This line while size <= 0 : print("Invalid Entry!\n") size = int(input("Enter the height of the pattern (must be greater than 0): ")) — Vivs, May 13 '21 at 05:03
Does this answer your question? [Asking the user for input until they give a valid response](https://stackoverflow.com/questions/23294658/asking-the-user-for-input-until-they-give-a-valid-response). And the code from [Creating a pyramid with numbers separated by asterisks](https://stackoverflow.com/q/67512014/1431750). — aneroid, May 13 '21 at 05:42

Black Raven · Answer 1 · 2021-05-17T10:51:00.800

You could add a condition to repeat the input loop if size is not greater than 0

space = '\t'
star = '*'

size = -1
while size <= 0:
    size = int(input("Enter the height of the pattern (must be greater than 0): "))
    if size <= 0 :
        print("Invalid Entry!\n")

for i in range(0, size) :
    star_count = 2 * i - 1

    line = space * (size - i - 1)

    if i == 0 :
        line += "1"
    else :
        line += str(2 * i) + space

    line += (star + space) * star_count

    if i > 0 :
        line += str(2 * i + 1)

    print(line)

So the output is

Enter the height of the pattern (must be greater than 0):  -2
Invalid Entry!

Enter the height of the pattern (must be greater than 0):  0
Invalid Entry!

Enter the height of the pattern (must be greater than 0):  3
        1
    2   *   3
4   *   *   *   5

score 0 · Accepted Answer · answered May 13 '21 at 05:09

What's wrong with for loop?

space = '\t'
star = '*'
while 1:
    size = int(input("Enter the height of the pattern (must be greater than 0): "))
    if size > 0:
        break
    print("Invalid Entry!")
    print("Please Try again.")

i = 0
while i < size:
    star_count = 2 * i - 1

    line = space * (size - i - 1)

    if i == 0 :
        line += "1"
    else :
        line += str(2 * i) + space

    line += (star + space) * star_count

    if i > 0 :
        line += str(2 * i + 1)
    i += 1

    print(line)

score 0 · Answer 3 · answered May 13 '21 at 05:13

The limitation to this code will be you always have to input 3 to get the answer which intend to get as per your query

space = '\t'
star = '*'
size = int(input("Enter the height of the pattern (must be greater than 0): "))

while size <= 0 :
    print("Invalid Entry!\n")
    size = int(input("Enter the height of the pattern (must be greater than 0): "))

for i in range(0, size) :
    star_count = 2 * i - 1

    line = space * (size - i - 1)
    if i == 0 :
        line += "1"
    else :
        line += str(2 * i) + space
    line += (star + space) * star_count
    if i > 0 :
        line += str(2 * i + 1)
    print(line)

Adding recursion and converting a for loop into a while loop

3 Answers3