Creating a diamond pattern using loops

Question

I am trying to write a program that reads an integer and displays, using asterisks, a filled diamond of the given side length. For Example, if the side length is 4, the prog

Answer 1

How about this:

n = 5
stars = [('*' + '**'*i).center(2*n + 1) for i in range(n)]

print('\n'.join(stars + stars[::-1][1:]))

The output:

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

This is similar to some of the answers above, but I find the syntax to be more simple and readable.

Answer 2

    def build(width):
        if width%2==0: 
            x=[(' *'*i).center(width*2,' ') for i in range(1,(width*2/2))]
        else: 
           x=[(' *'*i).center(width*2+1,' ') for i in range(1,((width*2+1)/2))]
        for i in x[:-1]+x[::-1]: print i

This worked for me for any positive width, But there are spaces padding the *s

Answer 3

Thanks Guys, I was able to formulate/correct my code based on the help I received. Thanks for all your input and helping the SO community!

if userInput > 0:              # Prevents the computation of negative numbers
    for i in range(userInput):
        for s in range (userInput - i) :    # s is equivalent to to spaces
            print(" ", end="")
        for j in range((i * 2) - 1):
            print("*", end="")
        print()
    for i in range(userInput, 0, -1):
        for s in range (userInput - i) :
            print(" ", end="")
        for j in range((i * 2) - 1):
            print("*", end="")
        print()

Answer 4

This might work better for you:

n = userInput

for idx in range(n-1):
    print((n-idx) * ' ' + (2*idx+1) * '*')
for idx in range(n-1, -1, -1):
    print((n-idx) * ' ' + (2*idx+1) * '*')

Output for userInput = 6:

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

Answer 5

How about the following:

side = int(input("Please input side length of diamond: "))

for x in list(range(side)) + list(reversed(range(side-1))):
    print('{: <{w1}}{:*<{w2}}'.format('', '', w1=side-x-1, w2=x*2+1))

Giving:

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

So how does it work?

First we need a counter that counts up to side and then back down again. There is nothing stopping you from appending two range lists together so:

list(range(3)) + list(reversed(range(3-1))

This gives you a list [0, 1, 2, 1, 0]

From here we need to work out the correct number of spaces and asterisks needed for each line:

  *        needs 2 spaces 1 asterix
 ***       needs 1 space  3 asterisks
*****      needs 0 spaces 5 asterisks

So two formulas are needed, e.g. for side=3:

x   3-x-1   x*2+1
0   2       1
1   1       3
2   0       5

Using Python's string formatting, it is possible to specify both a fill character and padding width. This avoids having to use string concatenation.

If you are using Python 3.6 or later, you can make use of f string notation:

for x in list(range(side)) + list(reversed(range(side-1))):
    print(f"{'': <{side - x - 1}} {'':*<{x * 2 + 1}}")