Python Boolean Variables

Python Boolean variables are set to either the True or False keywords. Both keywords require an Upper Case letter—lowercase letters are interpreted as normal variable or function names, so you could set true = True. A variable is of type Boolean if type(variable) results in the output <class 'bool'>. You can convert any object to a Boolean by using Python’s built-in function bool().

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

How to Convert an Integer Variable to a Boolean Variable?

You can convert an integer to a Boolean by using Python’s built-in function bool() any non-zero integer will result in a Boolean value of True. The only integer value that results in the Boolean False is the value 0.

>>> integer = 42
>>> boolean = bool(integer)
>>> boolean
True
>>> bool(0)
False

How to Convert a Float Variable to a Boolean Variable?

You can convert a float to a Boolean by using Python’s built-in function bool() any non-zero float will result in a Boolean value of True. The only float value that results in the Boolean False is the value 0.0.

>>> integer = 42.0
>>> boolean = bool(integer)
>>> boolean
True
>>> bool(0.0)
False

Boolean Logics Basics

Boolean logic is crucial for coding. Try finding any real-world code project that does not use boolean logic. You will most certainly fail. Hence, to become a code master, you must master boolean logic first.

This code shows the basic usage of boolean logic operators in Python.

# Logic Statements
A = True # Temperatures are high
B = True # Arctic ice is melting
C = True # Sea levels are rising
D = False # All regions become hot

def follows(A, B):
    """Returns True if 'B follows from A"""
    return not A or B

# Do we have a climate change?
climate_change = follows(follows(A, B), C)

if not D:
    print(climate_change)
else:
    print(D)

Before I show you the solution, take a guess—what’s the output of this code snippet?

We define four variables with various boolean assignments. Each boolean variable can be either True or False.

Consider two logical variables A and B. You have to understand three concepts.

  • The expression A and B is True, if and only if both variables A and B are already True.
  • The expression A or B is True, if and only if at least one variable is already True.
  • The expression not A is True, if and only if A is False.

In the code, we define our own function follows that takes two arguments A and B and returns A -> B.

In words: ‘The consequence B follows from the premise A’.

  • You can deduct anything from a wrong premise. Thus, A -> B is True if A is False.
  • You can deduct only true statements from a true premise. Thus, A -> B is True if B is True.

The result of our nested call of the follows function is True: (A -> B) -> C is True as all three variables are True. After passing the if condition, we state that climate change is indeed happening.

Related Boolean Video

Where to Go From Here?

Enough theory, let’s get some practice!

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