Printing octo-thorpes

Question

Given a number, for example, \$6\$, this Python function should print hashes in the following format:

     #
    ##
   ###
  ####
 #####
######

This is the function used to accomplish this:

def hash_print(number):
    for i in range(number):
        hashes='#' *(i+1)
        spaces=' '*(number -(i+1))
        print("%s%s") %(spaces,hashes)

Is there any way that this can be improved?

Answer 1

Python's str has justifying functions. The relevant one here would be rjust(). So we could just use that directly:

def hash_print(number):
    for i in range(number):
        hashes = '#' * (i+1)
        print hashes.rjust(number)

This is also \$O(n^2)\$ to build up hashes over time, so on the off chance that performance becomes a consideration, we could build it up as we go:

def hash_print(number):
    hashes = [' '] * number
    for i in range(number):
        hashes[number - i - 1] = '#'
        print ''.join(hashes)

Answer 2

You could do this on one line with join and a generator expression.

def hash_print(number):
    print ('\n'.join(('#' * (i + 1)).rjust(number) for i in range(number)))

A generator expression is like a for loop collapsed into a one line expression. It will loop over range(number) and create right justified strings of hashes, joining them together with newline characters in between them.

Also to note about some of your usages, you should put spaces between each operator, as it's easier to read. Changing this:

hashes='#' *(i+1)

to this:

hashes = '#' * (i + 1)

Also you should use str.format, not the % syntax for passing parameters to a string. str.format has a lot of useful formatting and is the accepted form nowadays. % is just older syntax. You can read about the usefulness of str.format here.

Though in your case they're both strings so you can just use string concatenation with the + operator:

    print( spaces + hashes )