What does the percentage sign mean in Python 3.1

Question

In the tutorial there is an example for finding prime numbers.

>>> for n in range(2, 10):
...     for x in range(2, n):
...         if n % x == 0:
...             print(n, 'equals', x, '*', n//x)
...             break
...     else:
...         # loop fell through without finding a factor
...         print(n, 'is a prime number')
...

I understand that the double == is a test for equality, but I don't understand the "if n % x" part. Like I can verbally walk through each part and say what the statement does for the example. But I don't understand how the percentage sign falls in. What does "if n % x" actually say?

Answer 1

In python 2.6 the '%' operator performed a modulus. I don't think they changed it in 3.0.1

The modulo operator tells you the remainder of a division of two numbers.

Answer 2

Modulus operator; gives the remainder of the left value divided by the right value. Like:

3 % 1 would equal zero (since 3 divides evenly by 1)

3 % 2 would equal 1 (since dividing 3 by 2 results in a remainder of 1).

Answer 3

It checks if the modulo of the division. For example, in the case you are iterating over all numbers from 2 to n and checking if n is divisible by any of the numbers in between. Simply put, you are checking if a given number n is prime. (Hint: You could check up to n/2).

Answer 4

The % does two things, depending on its arguments. In this case, it acts as the modulo operator, meaning when its arguments are numbers, it divides the first by the second and returns the remainder. 34 % 10 == 4 since 34 divided by 10 is three, with a remainder of four.

If the first argument is a string, it formats it using the second argument. This is a bit involved, so I will refer to the documentation, but just as an example:

>>> "foo %d bar"%5
'foo 5 bar'

However, the string formatting behavior is deprecated as of Python 3.1 in favor of the string.format() mechanism.