1.6. Operators¶
1.6.1. Comparison Operators¶
x < y
- Less thanx <= y
- Less or equalx > y
- Greater thanx >= y
- Greater or equalx == y
- Equalsx != 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 numbera
a ** (1/b)
-b
-th root of the numbera
>>> 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