range difference in Python 2.7 and Python 3

Question

I ran the following code on Python 2 and Python 3

i = int(input())
for j in range(i):
    k = int(input())
    print(k*k)%(1000000000+7)

the input was was fed from a file containing the following

2
2
1

The Python 2 version ran fine but Python 3 gave this error

4
Traceback (most recent call last):
  File "solution.py", line 4, in <module>
    print(k*k)%(1000000000+7)
TypeError: unsupported operand type(s) for %: 'NoneType' and 'int'

why is this error occurring in Python 3 and how do i correct it

In Python 3, print is a function, so k*k is an argument to print() and then the result of printing (None) is given the % operator. To fix, just put parentheses around the whole thing (excluding the actual print word, of course). — zondo
– zondo, Commented Nov 23, 2016 at 20:20
If you want to print the result of (k*k)% (1000000000+7) you have to wrap the whole thing in parenthesis: print((k*k) % (1000000000+7)). BTW: this produces the same result in both python and python3. (The output changes when you start using commas or keyword arguments...) — Bakuriu
– Bakuriu, Commented Nov 23, 2016 at 20:25

wim · Accepted Answer · 2016-11-23 20:24:51Z

2

In Python 2 it's parsing like this:

n = (k*k)%(1000000000+7)
print n

In Python 3 it's parsing differently, like this:

n = print(k*k)
n%(1000000000+7)  # TypeError

It's due to the changing of print from a statement into a function. The return code of the print function is None, which you can't use with the remainder operator %.

Make yourself aware also of the differences between input on Python 2 and Python 3

answered Nov 23, 2016 at 20:24

wim

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Comments

linusg · Accepted Answer · 2016-11-23 20:26:30Z

0

It has nothing to do with range. You're just trying to use modulo on None, that's what the print function returns. Just reorder the parantheses like this:

print((k*k)%(1000000000+7))

Hope this helps!

answered Nov 23, 2016 at 20:26

linusg

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