Python: Print a Hollow Square

Question

I've been trying to get this program to print a hollow square but I keep getting syntax errors, any help would be appreciated, thank you.

n=int(input('Please input an integer :')

cnt1 = 0

while (cnt1 < n)

print('*')

print('\n')

cnt1 = 0

while (cnt1 < (n-2)

print('*)

cnt2 = 0

while cnt2 < (n-2)

print (" ")

cnt2++

                   print("*\n")

cnt1++

cnt1 = 0

while(cnt1 < n)

print('*')

cnt1++

Answer 1

There are numerous problems with the code as you have pasted it, among them:

• Python has no ++ operator, you should use += 1 .
• Loops and conditionals need a colon : following them.
• The indentation is way off, Python is very picky about this.
• Many of your parentheses (and one single quote) are unbalanced.
• Printing generally involves a newline unless you specify something else with end= .

There may be others I forgot in the process of fixing the code but the following is probably more what you were after (assuming Python 3 due to your use of parentheses on the print and use of input rather than raw_input ):

n = int(input('Please input an integer : '))
cnt1 = 0
while cnt1 < n:
    print('*',end='')
    cnt1 += 1
print()
cnt1 = 0
while cnt1 < (n-2):
    print('*',end='')
    cnt2 = 0
    while cnt2 < (n-2):
        print (' ',end='')
        cnt2 += 1
    print('*')
    cnt1 += 1
cnt1 = 0
while cnt1 < n:
    print('*',end='')
    cnt1 += 1
print('\n')

Of course, there's no actual need for all those counter-controlled loops, Python provides a rich set of features for keeping your code short and maintainable (and you should generally always check user input for problems):

try:
    n = int(input('Please input an integer : '))
except:
    print('Problem with input, using ten instead.')
    n = 10
if n > 1:
    edge = '*' * n
    mid = '*%s*' % (' ' * (n-2))
    print(edge)
    for i in range(n-2): print(mid)
    print(edge)
else:
    print('Needs to be two or more')