python嵌套循环输出艺术和反向

Question

I am trying to write a program that looks something like this if, say, the input number was 6, or something like that the output should look like this:

         *
        **
       ***
      ****
     *****
    ******
     *****
      ****
       ***
        **
         *

but when I do it like I was told, this way specifically because this is what a classmate told me to do. :

    n = int(input("Enter a value for n: "))
    for i in range(1, n + 1):
        for j in range(n):
            if n - j > i:
               print(" ", end = " ")
            else:
               print("*", end = " ")
     print("")

    for i in range(1, n):
        for j in range(n):
            if n - j < i:
               print(" ", end = " ")
            else:
               print("*", end = " ")
    print("")

I get:

         *
        **
       ***
      ****
     *****
    ******
    *****
    ****
    ***
    **
    *

What am I doing wrong? Please tell me how to get it to correctly line up, I'd really appreciate it if someone could help me with this so I can learn to do this on my own, please assist me...

Answer 1

Your loops are a bit overcomplicated, so I've simplified somewhat:

n = int(input("Enter a value for n: "))

for x in range(n):
    out = ''
    for y in range(n-x):
        out = out +' '
    for y in range(x):
        out = out +'*'
    print(out)
for x in range(n):
    out = ''
    for y in range(x):
        out = out +' '
    for y in range(n-x):
        out = out +'*'
    print(out)

Enjoy!

Answer 2

If your assignment requires you to write the code exactly as you posted, Austin Kootz answer is the way to go.

However, a more simplifed way of doing this is using ljust

n = 6

for x in range(n - 1, 0, -1):
    print ''.ljust(x, ' ') + '*'.ljust(n - x, '*')

for x in range(n):
    print ''.ljust(x, ' ') + '*'.ljust(n - x, '*')

Answer 3

What you want in the second set of loops is to take the row number (counting from 1) and print that many spaces (" "), and then print asterisks ("*") for the rest of the row. So if i is the row number and j the column number (and indexing starts from 0), you should print " " while j < i + 1 and "*" otherwise. This gives:

# The top part of the pyramid
for i in range(1, n + 1):
    for j in range(n):
        if n - j > i:
            print(" ", end = " ")
        else:
            print("*", end = " ")
    print("")
# The bottom half of the pyramid
for i in range(n):
    for j in range(n):
        # Print spaces in the beginning of the row
        # (while the column number is less than the row number)
        if j < i + 1:
           print(" ", end = " ")
        # Print asterisks for the rest of the row
        else:
           print("*", end = " ")
    print("")