Python Booleans

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Index

1. Definition
2. Evaluate Values and Variables
3. Comparison operators return Boolean values
4. Functions can Return a Boolean

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Definition

In programming you often need to know if an expression is True or False

Evaluate Values and Variables

You can evaluate any expression in Python, and get one of two answers, True or `False.

• The bool() function allows you to evaluate any value, and give you True or False in return,

When you compare two values, the expression is evaluated and Python returns the Boolean answer:

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

Most Values are True

• Almost any value is evaluated to True if it has some sort of content.
  • Any string is True, except empty strings.
  • Any number is True, except 0.
  • Any list, tuple, set, and dictionary are True, except empty ones.

Some Values are False

• In fact, there are not many values that evaluate to False, except empty values, such as (), [], {}, "", the number 0, and the value None. And of course the value False evaluates to False.

bool(False)  # Output: False
bool(None)   # Output: False
bool(0)      # Output: False
bool("")     # Output: False
bool(())     # Output: False
bool([])     # Output: False
bool({}).    # Output: False

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Comparison operators return Boolean values

When you compare two values, the expression is evaluated and Python returns the Boolean answer:

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

Particular cases:

print(1 == True)   #Output: True
print(0 == False)  #Output: True
print(1 == 1.0000) #Output: True

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Functions can Return a Boolean

You can create functions that returns a Boolean Value:

def myFunction() :  
  return True  
  
if myFunction():  
  print("YES!")  
else:  
  print("NO!")

Python also has many built-in functions that return a boolean value, like the isinstance() function, which can be used to determine if an object is of a certain data type:

x = 200  
print(isinstance(x, int))

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