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5.3. Boolean Data Type

The boolean data type is either True or False. In Python, boolean variables are defined by the True and False keywords.

>>> a = True
>>> type(a)
<class 'bool'>

>>> b = False
>>> type(b)
<class 'bool'>

The output <class 'bool'> indicates the variable is a boolean data type.

Note the keywords True and False must have an Upper Case first letter. Using a lowercase true returns an error.

>>> c = true
Traceback (most recent call last):
  File "<input>", line 1, in <module>
NameError: name 'true' is not defined
   
>>> d = false
Traceback (most recent call last):
  File "<input>", line 1, in <module>
NameError: name 'false' is not defined

5.3.1. Integers and Floats as Booleans

Integers and floating point numbers can be converted to the boolean data type using Python’s bool() function. An int, float or complex number set to zero returns False. An integer, float or complex number set to any other number, positive or negative, returns True.

>>> zero_int = 0
>>> bool(zero_int)
False

>>> pos_int = 1
>>> bool(pos_int)
True

>>> neg_flt = -5.1
>>> bool(neg_flt)
True

5.3.2. Boolean Arithmetic

Boolean arithmetic is the arithmetic of true and false logic. A boolean or logical value can either be True or False. Boolean values can be manipulated and combined with boolean operators. Boolean operators in Python include and, or, and not.

The common boolean operators in Python are below:

  • or

  • and

  • not

  • == (equivalent)

  • != (not equivalent)

In the code section below, two variables are assigned the boolean values True and False. Then these boolean values are combined and manipulated with boolean operators.

>>> A = True
>>> B = False

>>> A or B
True

>>> A and B
False

>>> not A
False

>>> not B
True

>>> A == B
False

>>> A != B
True

Boolean operators such as and, or, and not can be combined with parenthesis to make compound boolean expressions.

>>> C = False
>>> A or (C and B)
True
>>> (A and B) or C
False

A summary of boolean arithmetic and boolean operators is shown in the table below:

A

B

not A

not B

A == B

A =! B

A or B

A and B

T

F

F

T

F

T

T

F

F

T

T

F

F

T

T

F

T

T

F

F

T

F

T

T

F

F

T

T

T

F

F

F