Python Booleans

Booleans are a fundamental data type in Python that represent one of two values: True or False. They are primarily used for logical operations, conditional statements, and control flow in Python.

Boolean Values

In Python, you often need to determine whether an expression is True or False. You can evaluate expressions, and Python will return either True or False as the result.

Comparing Values

When you compare two values, Python evaluates the expression and returns the corresponding Boolean value:

print(10 > 9)  # True
print(10 == 9) # False
print(10 < 9)  # False

Using Booleans in if Statements

In conditional statements, Python evaluates conditions to determine whether they are True or False. Based on the result, it executes the appropriate block of code:

a = 200
b = 33

if b > a:
  print("b is greater than a")
else:
  print("b is not greater than a")

Evaluating Values and Variables

The bool() function allows you to evaluate any value or variable and return True or False:

print(bool("Hello"))  # True
print(bool(15))       # True

x = "Hello"
y = 15
print(bool(x))         # True
print(bool(y))         # True

Most Values Are True

In Python, most values are considered True if they contain some content. For example:

• Any non-empty string is True.

• Any number is True unless it's 0.

• Any non-empty list, tuple, set, or dictionary is True.

print(bool("abc"))                         # True
print(bool(123))                           # True
print(bool(["apple", "cherry", "banana"])) # True

Some Values Are False

There are very few values that evaluate to False. These include:

• Empty values like (), [], "", {}, and 0.

• The special value None.

• The value False.

print(bool(False))   # False
print(bool(None))    # False
print(bool(0))       # False
print(bool(""))      # False
print(bool(()))      # False
print(bool([]))      # False
print(bool({}))      # False

Additionally, objects created from classes with a __len__ function that returns 0 or False will evaluate to False.

class myclass:
  def __len__(self):
    return 0

myobj = myclass()
print(bool(myobj))  # False

Functions Can Return a Boolean

You can create functions that return Boolean values. These functions can be used to execute code based on the returned value:

def myFunction():
  return True

print(myFunction())  # True

You can use the result of a function in conditional statements:

def myFunction():
  return True

if myFunction():
  print("YES!")
else:
  print("NO!")

Python also provides built-in functions that return Boolean values. For example, the isinstance() function can be used to check if an object is of a specific data type:

x = 200
print(isinstance(x, int))  # True

Booleans are a fundamental part of Python, enabling you to make decisions and control the flow of your programs based on conditions and logic.