Question

I am attempting to clear lines of code in Python and came across a post at Any way to clear python's IDLE window? on how to do so however when I run the function below in IDLE 3.3 I get the error below. It does however work in version 2.7.3.

ERROR

Traceback (most recent call last):
  File "<pyshell#7>", line 1, in <module>
    cls()
  File "<pyshell#6>", line 2, in cls
    print('\n') * 100
TypeError: unsupported operand type(s) for *: 'NoneType' and 'int'

CODE

def cls():
    print('\n') * 100

Answer 1

You probably mean

print('\n' * 100)

When you multiply a string by an int, it is repeated:

>>> 'ha' * 3
'hahaha'

But what you do is multiply the value of print('\n') by 100. But print() doesn’t return anything (read: returns None), hence the error: you can’t multiply None and int.

In Python 2 there is no difference, because there are no parentheses:

print '\n' * 100

Still, it’s interpreted by Python the same way as in Python 3 (and not the same way you seem to iterpret it).