Everything You Need To Know About Booleans in python

Booleans are the most important aspects of programming languages. Because they give codes the power to make decisions. It is only right to learn everything about them. When we compare two values in Python, we get a boolean answer.

In Python, booleans can have two values.

True
False

In Python, only True and False are Boolean class values.

Python

## get class names of Boolean value  True and False
print(type(True))
print(type(False))

Output

<class 'bool'>
<class 'bool'>

Python

Substitute Booleans

Python has a unique take on boolean values, you can use any class objects as boolean values.

In a conditional statement, if any return type or value of an object is not 0, False, None, or Empty then everything else is True.

Python

# Use bool to turn values into boolean.
  False values                                        Output
print('False Values')                              False Values
print('bool(0) \t',end='')             
print(bool(0))                                     bool(0) 	False
print('bool(False) \t',end='')         
print(bool(False))                                 bool(None) 	False  
print('bool() \t',end='')
print(bool())                                      bool(None) 	False
print('bool(None) \t',end='')
print(bool(None))                                  bool(None) 	False

Python

  True values                                          Output
print('True Values')                               True Values 
print('bool(1) \t',end='')                      
print(bool(1))                                     bool(1) 	True
print('bool(True) \t',end='')
print(bool(True))                                  bool(True) 	True
print('bool("this is a string") \t',end='')
print(bool('this is a string'))                    bool('this is a string') 	True
lis=[1,2,3]
print(f'{bool(lis)} \t',end='')
print(bool(lis))                                   bool([1,2,3])

Numbers are used as boolean values.

Python offers numbers to be used as boolean values; any number other than 0 is considered True.

Python

# True is greater than 10                        Output
print(True>10)                                   False 
# False is equal to ,is equal to -1
print(False==-1)                                 False 
# True is equal to ,is equal to 1
print(True==1)                                   True     
# False is equal to ,is equal to 0
print(False==0)                                  True

Python

# false plus false is zero                    Output
print(False+False)                              0
# true adds to true equals to two.
print(True+True)                                2

Numbers in Conditional Statements

Let’s use numbers as boolean values in conditional statements.

As previously stated, when it comes to numbers, a boolean value of ‘0’ is False.
Any number other than 0 is True.

Python

# use 0 as false
if 0:
    print('True')
else:
    print('False')

Output

False

Python

# use any number but 0 as false
if 1:
    print('True')
else:
    print('False')

Output

True

Python

# 25 as true
if 25:
    print('True')
else:
    print('False')

Output

True

Python

# -120 as true
if -120:
    print('True')
else:
    print('False')

Output

True

Python

Boolean Operators

not operator
and operator
or operator

A	B	not A	not B	A and B	A or B
True	True	False	False	True	True
True	False	False	True	False	True
False	True	True	False	False	True
False	False	True	True	False	False

As you can see, the above operators operate on boolean values.

Let’s look at some examples of these operators.

Python

# see how or is used
print('  A       B   \tResult')
print('True or False \t',end='')
print(True or False)
# use true or true  with or operator
print('True or True \t',end='')
print(True or True)
# use false or false  with or operator
print('False or False \t',end='')
print(False or False)

Output

  A       B   	Result
True or False 	True
True or True 	True
False or False 	False

Python

# see how and is used 
print('  A       B   \tResult')
print('True and False\t',end='')
print(True and False)
print('False and False\t',end='')
print(False and False)
print('True and True\t',end='')
print(True and True)

Output

  A       B   	Result
True and False	False
False and False	False
True and True	True

Python

“not” is used to negate a statement’s value.

Python

# see how to use not.
print('Statement\tOutput',end='')
print('not True\t',end='')
print(not True)
print('not False\t',end='')
print(not False)
print('not (False and False)\t',end='')
print(not(False and False))

Output

Statement               Output 
not True	        False
not False	        True
not (False and False)	True

Python

Comparison Operator

Equal to ==
Not Equal to !=
Greater than >
Lesser Than <
Greater than or Equal to >=
Lesser than or Equal to <=
is operator
in operator

A boolean value is returned by comparison operators. When a statement is executed, it returns a boolean value.

**1. `is equal` to (==) operator**

Python

# 'Apple' is equal to 'Apple'
print('Apple'=='Apple')
# 'Apple' is equal to 'Cherry Blossom'
print('Apple'=='Cherry Blossom')

Output

True
False

Python

2. `is not` equal to (!=) operator

Python

# 'Apple' is not equal to 'Cherry Blossom'
print('Apple'!='Cherry Blossom')
# 4 is not equal to 5
print(4!=5)

Output

True
True

Python

**3. `Greater than` (>) operator**

Python

a=4
b=9
c=14
# b is greater than a 
b>a
# a is greater than b 
a>b

Output

True
False

Python

**4. `Less than` (<) operator**

Python

a=4
b=9
c=14
# b is lesser than a 
b<a
# a is lesser than c 
a<c

Output

False
False

Python

**5. `Greater than or equal to` `(>=`) operator**

Python

# c is greater than equal to a
a=4
b=9
c=14
c>=a

Output

True

Python

**6. `Lesser than or equal to` `(<=` ) operator**

Python

# c is lesser than equal to b
a=4
b=9
c=14
c<=b

Output

True

Python

7. `in` operator

In operator is used to find values in iterable objects.

Python

# find 'apple' in string
string='An apple a day, keeps the doctor away'
print('apple' in string)

# find 'banana' in string
print('banana' in string)

# confirm if there is not 'banana' in string
print('banana' not in string)

Output

True
False
True

Python

These statements can be used in code logic to control the flow of code.

Python

# use in operator to control flow of logic.
if 'apple' in string:
    print('Apple is present')
elif 'banana' in string:
    print('Banana is present')
if 'banana' not in string:
    print('banana is not present')

Output

Apple is present
banana is not present

Python

8. operator `is`

Unlike the symbol operator, this operator works on the identity of objects.
It returns True if the compared objects are identical.

operator `is not`

The is not operator is the inverse of is.
It returns True when the given objects are not identical.

Python

# find if a is b
a=5
b=5
c=4
print(a is b)
# find if a is not c
print(a is not c)

Output

True
True

Python

a=[1,2,3,4,5]
b=[1,2,3,4,5]
# find if the list a is equal to b list
print(a is b)
# find if the list a is not equal to b list
print(a is not b)

Output

True
False

Python

Other data types, such as lists, sets, and tuples, can also be compared.

Python

a=[1,2,3,4,5]
b=[1,2,3,4,5]
# find if the list a is equal equal to b list
print(1,a==b)

a=(1,2,3,4,5)
b=(1,2,3,4,5,6)
# find if the tuple a is not equal to b tuple
print(2,a!=b)

a={1,2,3,4,5,6}
b={1,2,3,4,5}
# find if the set a is greater than b set
print(3,a>b)

a={1:1,2:2,3:3,4:4,5:5}
b={1:1,2:2,3:3,4:4,5:5}
# find if the dictionary a is equal to equal to b dictionary
print(4,a==b)

Output

1 True

2 True

3 True

4 True

Python

Chaining Comparison Operators

We can chain comparisons together.
For logic development, we can chain comparisons together and separate them with ‘and’/’or’ operators.

Python

# chain comparison operators
# 1 is less than 8 is greater than
print(1, 1 < 8 > 7)
# 1 is greater than 8 is greater than
print(2, 1 > 8 > 7)
# 1 is less than 8 is less than
print(3, 1 < 8 < 7)
# 1 is less than or 8 is less than
print(4, 1 < 8  or 8 < 7)
# 1 is less than or 8 is greater than
print(5, 1 < 8  and 8 > 7)

Output

1 True
2 False
3 False
4 True
5 True

Python

Range selection using comparison operators and chaining operators

Python

# create a list
num=[x for x in range(25)]
print(num)

Output

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24]

Python

As you can see from the list above, there are 25 numbers. Let’s look at the Range selection.

Python

# print numbers greater than 10
for i in num:
    if i>10:
        print(i,end=' ')

Output

11 12 13 14 15 16 17 18 19 20 21 22 23 24

Python

# print numbers lesser than 10
for i in num:
    if i<10:
        print(i,end=' ')

Output

0 1 2 3 4 5 6 7 8 9

Python

In the preceding examples, we saw ranges of greater than and less than ten. Let’s try picking a particular number from a group now.

Python

# print numbers greater than 10 and less than 18
for i in num:
    if i>10 and i<18:
        print(i,end=' ')

Output

11 12 13 14 15 16 17

Python

# print numbers less than 10 and great  than 4
for i in num:
    if i<10 and i>4:
        print(i,end=' ')

Output

5 6 7 8 9

Python

Be cautious when configuring range conditions.

Python

# print numbers greater than 10 and lesser  than 0
for i in num:
    if i>10 and i<0:
        print(i,end=' ')

Output

11 12 13 14 15 16 17 18 19 20 .......... Ꝏ

Python

Priority

When it comes to chaining with comparison operators, boolean operators, like arithmetic operators, have a defined precedence.
In this order: 1.’not’ 2.’and’ 3.’or’

Python

# create a list of prime and odd numbers
prime=[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43,  47]
odd=[x for x in range(51) if x%2==1]
print(prime)
print(odd)

Output

[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47]
[1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, 43, 45, 47, 49

Python

Logic Chaining

Python

# create a large chain rule
not 1 < 8  and 8 < 7 or 1 > 7 and 1 < 8

Output

False

Python

Nested Chain Rule

Python

# create a large chain rule
not (1 < 8  and 8 < 7 or 1 > 7 and 1 < 8)

Output

True

Python

As shown in the preceding example, changing the order of these chains can result in a change in logic.

Exercise caution when constructing chains in your code.

Short Circuit

As an efficiency measure in Python, operators are supposed to short circuit if their output is confirmed.
The reason for the short circuit
In a and statement, if the first value is False, the result is obviously False.
Similarly, if the first value in an or statement is True, the result is True.

Check out the example below.

Python

# Creating a Short circuit example by avoiding an inevitable error
True or 1/0

Output

True

Python

In the preceding example, a divided by zero exception should have occurred, but it did not because the statement short-circuited.

Following will cause error because there is False or, first statement false will enable the compiler to check the next statement which is 1/0, and it will cause divided by zero error.

Python

# Creating a Short circuit example by avoiding an inevitable error
False or 1/0

Output

---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
<ipython-input-43-4197a8a91ebb> in <module>
      1 # Creating a Short circuit example by avoiding an inevitable error
----> 2 False or 1/0

ZeroDivisionError: division by zero

Python

This error is avoided because it is cut off by the obvious conclusion of “false” and being false.

False and False == False
False and True == False

Python

False and 1/0

Output

False

Python

The above statement didn’t cause an error because and requires both conditions to be True . So if there is one False statement other statement won’t matter whether it is true or false, the result will be False.

Sequenced Boolean datatypes

Python returns a True value if a sequenced datatype is not empty.
An empty datatype will return False.

Dictionary, List, Tuple, and Byte are used for creating boolean values.

Tuple

Python

# tuple as boolean
a=()
bool(a)

Output

False

Python

Bytes

Python

# bytes as boolean
a=bytes()
bool(a)

Output

False

Python

# bytes as boolean
a=bytes()
bool(a)

Output

False

Python

# bytes as boolean
a=bytes(123)
bool(a)

Output

O/P:
True

Python

Dictionary

Python

# dictionary as boolean
a={}
bool(a)

Output

False

Python

# dictionary as boolean
a={1:2,3:4}
bool(a)

Output

True

Python

# list as boolean
a=[1,2,3,4]
bool(a)

Output

True

Python

Boolean Values for Function Objects and Classes

If you use functions for booleans, they will always return True.
Classes are always True by default, but they can be programmed to be False.

Python

# create a hollow function
def function1():
    pass
# use function as bool value
bool(function1)

Output

True

Python

However, if you call a function, it will be dependent on what it returns.

function1 does not return a value, so it is None, and None in Python is false.
The only difference is the presence of parenthesis, which alters the output.

Python

# using function returntype as bool value.
def function1():
    pass
bool(function1())

Output

False

Python

# using function returntype as bool value.
def function1():
    return True
bool(function1())

Output

True

Python

# using function returntype as bool value.
def function1():
    return None
bool(function1())

Output

False

Python

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