1.6. Operators

1.6.1. Comparison Operators

  • x < y - Less than

  • x <= y - Less or equal

  • x > y - Greater than

  • x >= y - Greater or equal

  • x == y - Equals

  • x != y - Not Equals

>>> 10 < 2
False
>>>
>>> 10 <= 2
False
>>>
>>> 10 > 2
True
>>>
>>> 10 >= 2
True
>>>
>>> 10 == 2
False
>>>
>>> 10 != 2
True

>>> x = 10
>>> y = 2
>>>
>>> x >= 2
True

>>> 0 == -0
True

1.6.2. Arithmetic Operators

  • + - Addition

  • - - Subtraction

  • * - Multiplication

  • / - Division

>>> 10 + 2
12
>>>
>>> 10 - 2
8
>>>
>>> 10 * 2
20
>>>
>>> 10 / 2
5.0

>>> x = 10
>>> y = 2
>>>
>>> x + y
12

1.6.3. Power and Root

  • a ** b - b power of the number a

  • a ** (1/b) - b-th root of the number a

>>> 10 ** 2
100
>>>
>>> 2 ** -1
0.5
>>>
>>> 1.337 ** 3
2.389979753

>>> 4 ** (1/2)
2.0
>>>
>>> 2 ** (1/2)
1.4142135623730951
>>>
>>> 27 ** (1/3)
3.0

>>> 4 ** 0.5
2.0
>>>
>>> 2 ** 0.5
1.4142135623730951
>>>
>>> 27 ** 0.333
2.9967059728946346

1.6.4. Divisions

There are three (and even four if counting divmod) ways of dividing numbers in Python:

  • / - True Division (changes type to float)

  • // - Floor division (preserving data type)

  • % - Modulo division (reminder)

The most common is true division, which changes type to float to preserve mathematical correctness:

>>> 12 / 6
2.0
>>>
>>> 12 / 5
2.4

Note, that the floor division preserves types, so it is more correct in computer science way. However it will produce invalid values from math perspective:

>>> 12 // 6
2
>>>
>>> 12 // 5
2

There is also a modulo division, which is more frequently used than you might think. Modulo division is the reminder from true division:

>>> 12 % 6
0
>>>
>>> 12 % 5
2

Modulo division is most frequently used to test if value is even or odd. In such case, you need to modulo divide number by 2 and check the reminder. If the reminder is 0, than the original number was even, if the reminder is false, the original number was odd:

>>> 12 % 2 == 0
True
>>>
>>> 11 % 2 == 0
False

1.6.5. Increment Operators

In Python for each operator there is also an increment version of it:

  • += - Incremental addition

  • += - Incremental subtraction

  • *= - Incremental multiplication

  • **= - Incremental power

  • /= - Incremental true division

  • //= - Incremental floor division

  • %= - Incremental modulo division

However, most of a time only += and += are used. Others are very rare.

>>> x = 10
>>> x = x + 1
>>>
>>> print(x)
11

>>> x = 10
>>> x += 1
>>>
>>> print(x)
11

>>> x = 10
>>> x -= 1
>>>
>>> print(x)
9

>>> x = 1
>>> x++
Traceback (most recent call last):
SyntaxError: invalid syntax

>>> x = 1
>>> ++x
1