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Functions / Modulus 

In Python integer division returns floor division
Modulus always return a number with the same sign

25 % 7 == 4

Positive

In Python integer division always return floor division. 
 
"""Modulus operation 
Python always does floor division
dividend % divisor = reminder
"""

assert 0 % 7 == 0
assert 1 % 7 == 1
assert 3 % 7 == 3  # 3//7 = 0 reminder 3
assert 7 % 7 == 0
assert 8 % 7 == 1
assert 9 % 7 == 2
assert 25 % 7 == 4
assert 7 % 25 == 7 # 7//25 = 0 reminder 7

print('Tests passed')

Negative

Python modulus always return a number with the same sign as the denominator. 
 
"""Modulus with negative numbers

In Python (%) returns same sign as the denominator
  23 = 4*5 + 3      # reminder 3
  23 = -5* 5 - 2    # reminder -2
  -3 = -1*7 + 4     # remainder 4

Python applies distribute law of Modulo
  (a + b) mod n = ((a mod n) + (b mod n)) mod n
  (2 + 2) % 3 = (2%3 + 2%3) % 3 = 1
"""

assert (2 + 2) % 3 == 1 # distribute law of Modulo
assert (2 + 2) % 3 == (2%3 + 2%3) % 3 == 1
assert (2 + 2) % 3 != 2%3 + 2%3

assert 23 % 5 ==  3     # reminder 3
assert 23 % -5 == -2    # same sign as denominator
assert -3 % 7 == 4

assert 23 // 5  ==  4   # floor division
assert 23 // -5 == -5
assert -3 // 7 == -1

print('Tests passed')




References