# 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.

## Where to Go From Here?

Enough theory, let’s get some practice!

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