bool

Properties

>>> dir(bool)
['__abs__', '__add__', '__and__', '__bool__', '__ceil__', '__class__', '__delattr__', '__dir__', '__divmod__', '__doc__', '__eq__', '__float__', '__floor__', '__floordiv__', '__format__', '__ge__', '__getattribute__', '__getnewargs__', '__gt__', '__hash__', '__index__', '__init__', '__init_subclass__', '__int__', '__invert__', '__le__', '__lshift__', '__lt__', '__mod__', '__mul__', '__ne__', '__neg__', '__new__', '__or__', '__pos__', '__pow__', '__radd__', '__rand__', '__rdivmod__', '__reduce__', '__reduce_ex__', '__repr__', '__rfloordiv__', '__rlshift__', '__rmod__', '__rmul__', '__ror__', '__round__', '__rpow__', '__rrshift__', '__rshift__', '__rsub__', '__rtruediv__', '__rxor__', '__setattr__', '__sizeof__', '__str__', '__sub__', '__subclasshook__', '__truediv__', '__trunc__', '__xor__', 'as_integer_ratio', 'bit_count', 'bit_length', 'conjugate', 'denominator', 'from_bytes', 'imag', 'numerator', 'real', 'to_bytes']

Definition

A Boolean value (bool) is a logical value: True or False. It answers questions like “Is this statement correct?” For instance, 1 == 2 is False.

bool is a subclass of int, so in many circumstances booleans are evaulated like numbers.

Using booleans

If a statement is true then it will evaluate to True. Conversely, if a statement is false then it will evaluate to False.

>>> 1 == 1
True

>>> 1 == 2
False

>>> "Hello" == "World"
False

>>> "Hello" == "Hello"
True

Types with falsy values

The boolean value of an empty type will always be False.

Type	Example	Notes
`bool`	`False`	The literal `False` itself
`NoneType`	`None`	Represents “no value”
`int`, `float`, `complex`	`0`, `0.0`, `0j`	Any numeric zero
`str`	`""`	Empty string
`list`	`[]`	Empty list
`tuple`	`()`	Empty tuple
`dict`	`{}`	Empty dictionary
`set`	`set()`	Empty set
`frozenset`	`frozenset()`	Empty frozen set
`range`	`range(0)`	Empty range object

Likewise a custom class that ony returns 0 or False will be falsy.

Types with truthy values

The boolean value of a non-empty type will always be True.

Type	Example	Notes
`bool`	`True`	The literal `True`
`int`, `float`, `complex`	`1`, `3.14`, `-2+0j`	Any nonzero
`str`	`"Hello"`	Any non-empty string
`list`	`[1, 2, 3]`	Any non-empty list
`tuple`	`(1, 2)`	Any non-empty tuple
`dict`	`{"a": 1}`	Any non-empty dictionary
`set`	`{"x", "y"}`	Any non-empty set
`frozenset`	`frozenset({1})`	Any non-empty frozen set
`range`	`range(1, 5)`	Any range with at least one value

Checking for truthiness

The boolean value of a type can be checked by using the bool() function.

>>> bool("")
False

>>> bool(0)
False

>>> bool("99 problems but a bool aint one")
True

Operations: Truth tables

The `and` operator

Expression	Result	Explanation
`True and True`	`True`	Both values are true
`True and False`	`False`	One is false
`False and True`	`False`	One is false
`False and False`	`False`	Both are false

The `or` operator

Expression	Result	Explanation
`True or True`	`True`	At least one is true
`True or False`	`True`	First value is true
`False or True`	`True`	Second value is true
`False or False`	`False`	Both are false

The `not` operator

Expression	Result	Explanation
`not True`	`False`	Negates the value
`not False`	`True`	Negates the value

Dunder methods

Dunder Method	Operation	Example (normal syntax)	Example (dunder call)
`__bool__`	Truth value	`bool(True)` → `True`	`True.__bool__()`
`__and__`	Logical AND / Bitwise `&`	`True & False` → `False`	`True.__and__(False)`
`__or__`	Logical OR / Bitwise `\|`	`True \| False` → `True`	`True.__or__(False)`
`__xor__`	Logical XOR / Bitwise `^`	`True ^ False` → `True`	`True.__xor__(False)`
`__invert__`	Bitwise NOT	`~True` → `-2`	`True.__invert__()`
`__eq__`	Equality comparison	`True == False` → `False`	`True.__eq__(False)`
`__ne__`	Inequality comparison	`True != False` → `True`	`True.__ne__(False)`
`__lt__`	Less than	`False < True` → `True`	`False.__lt__(True)`
`__le__`	Less than or equal	`True <= True` → `True`	`True.__le__(True)`
`__gt__`	Greater than	`True > False` → `True`	`True.__gt__(False)`
`__ge__`	Greater than or equal	`True >= False` → `True`	`True.__ge__(False)`
`__add__`	Addition	`True + True` → `2`	`True.__add__(True)`
`__sub__`	Subtraction	`True - False` → `1`	`True.__sub__(False)`
`__mul__`	Multiplication	`True * 5` → `5`	`True.__mul__(5)`
`__int__`	Convert to integer	`int(True)` → `1`	`True.__int__()`
`__float__`	Convert to float	`float(False)` → `0.0`	`False.__float__()`
`__index__`	Integer index value	`[10, 20][True]` → `20`	`True.__index__()`
`__str__`	String conversion	`str(True)` → `'True'`	`True.__str__()`
`__repr__`	Representation	`repr(True)` → `'True'`	`True.__repr__()`
`__hash__`	Hash value	`hash(True)` → `1`	`True.__hash__()`

Boolean methods

All boolean methods are inherited from int.

`as_integer_ratio`

Returns a tuple (numerator, denominator) representing the boolean as a fraction.

>>> True.as_integer_ratio()
(1, 1)

>>> False.as_integer_ratio()
(0, 1)

`bit_count`

Returns the number of 1 bits in the integer representation of the boolean.

>>> True.bit_count()
1

>>> False.bit_count()
0

`bit_length`

Returns the number of bits required to represent the boolean as an integer, excluding the sign bit.

>>> True.bit_length()
1

>>> False.bit_length()
0

`conjugate`

Returns the complex conjugate of the boolean value. Since booleans are real-valued, this just returns the same integer value (1 or 0).

>>> True.conjugate()
1

>>> False.conjugate()
0

`denominator`

Returns the denominator of the boolean when viewed as a rational number. It is always 1.

>>> True.denominator
1

>>> False.denominator
1

`from_bytes`

Class method that returns a boolean created from a sequence of bytes. Any non-zero value becomes True; zero becomes False. It is the inverse of to_bytes.

>>> int.from_bytes(b"\x01", "big") != 0
True
>>> bool(int.from_bytes(b"\x00", "big"))
False

Note: from_bytes is defined on int; booleans use the same implementation via inheritance.

`imag`

The imaginary part of the boolean when viewed as a complex number. Always 0.

>>> True.imag
0
>>> False.imag
0

`numerator`

The numerator of the boolean when viewed as a fraction. True has numerator 1; False has numerator 0.

>>> True.numerator
1
>>> False.numerator
0

`real`

The real part of the boolean when viewed as a complex number. This is the same as its integer value (1 or 0).

>>> True.real
1
>>> False.real
0

`to_bytes`

Convert the boolean (as an integer) to a bytes object using a given length and byte order.

>>> True.to_bytes(1, "big")
b'\x01'
>>> False.to_bytes(1, "big")
b'\x00'

Properties​

Definition​

Using booleans​

Types with falsy values​

Types with truthy values​

Checking for truthiness​

Operations: Truth tables​

The and operator​

The or operator​

The not operator​

Dunder methods​

Boolean methods​

as_integer_ratio​

bit_count​

bit_length​

conjugate​

denominator​

from_bytes​

imag​

numerator​

real​

to_bytes​