stuck with python, please advise

so im trying to make it so that pressing enter without inputting any value, will break the loop, however, an empty string can be used because of
for i in range(len(x_str_array)):
x[i] = int(x_str_array[i]) bit.

'Exercise 7.3'

# modified program from exercise 7.2

a=1
z=""
while x !=z:
x_str = raw_input('Enter Start,Stop,Increment: ')
if x==z:
break
else:
x_str_array = x_str.split(',') # splits the string where a comma pops up
x = range(len(x_str_array)) # Preallocation step- makes x= the same length as x_str_array
for i in range(len(x_str_array)):
x[i] = int(x_str_array[i])
a=x[0]
b=x[1]
c=x[2]
for number in range(a,b,c):
print "number:", number, " square:", number**2, " cube:", number**3



please advise me on this.

p.s yes i am a complete novie, haha :confused:

i thought maybe using an empty tuple or list or something, but that wouldn't work either.

so that pressing enter without inputting any value, will break the loop

while True:
# Get some user input.
x_str = raw_input("Someting: ")
# If the user simply hits enter or supplies a string full of spaces, break.
if not x_str or x_string.isspace():
break
# More stuff here.

Happy new year! :D