> ## Documentation Index
> Fetch the complete documentation index at: https://docs.syntblaze.com/llms.txt
> Use this file to discover all available pages before exploring further.
# Python Logical NOT
The `not` operator is a unary logical operator that performs boolean negation. It evaluates the truthiness of a single operand and returns the inverted boolean value: `True` if the operand is considered false, and `False` if the operand is considered true.
```python theme={"dark"}
not expression
```
## Evaluation Mechanics
Unlike Python's `and` and `or` operators, which can return the operands themselves, the `not` operator strictly guarantees a return type of `bool`. It forces the operand into a boolean context using Python's internal truth value testing.
1. **Truthiness:** If the operand evaluates to `True` (truthy), `not` returns `False`.
2. **Falsiness:** If the operand evaluates to `False` (falsy), `not` returns `True`.
In Python, the following standard values are inherently falsy:
* Constants defined to be false: `None` and `False`.
* Zero of any numeric type: `0`, `0.0`, `0j`, `Decimal(0)`, `Fraction(0, 1)`.
* Empty sequences and collections: `''`, `()`, `[]`, `{}`, `set()`, `range(0)`.
All other values are considered truthy by default.
```python theme={"dark"}
# Standard boolean negation
print(not True) # False
print(not False) # True
# Negation of falsy objects
print(not None) # True
print(not 0) # True
print(not []) # True
# Negation of truthy objects
print(not 1) # False
print(not "Data") # False
print(not [1, 2]) # False
```
## Object-Level Implementation
Under the hood, `not x` is evaluated by calling `bool(x)` and inverting the result. The `bool()` built-in determines truthiness by looking for specific magic methods (dunder methods) on the object's class:
1. Python first checks for the `__bool__()` method. If it exists, `not` returns the inverse of what `__bool__()` returns.
2. If `__bool__()` is not defined, Python falls back to `__len__()`. If `__len__()` returns `0`, the object is falsy (so `not` returns `True`). If it returns a non-zero integer, the object is truthy (so `not` returns `False`).
3. If neither method is defined, the object is considered truthy by default, and `not` will return `False`.
## Operator Precedence
The `not` operator has a lower precedence than non-boolean operators (like arithmetic, bitwise, and comparison operators) but a higher precedence than the logical operators `and` and `or`.
```python theme={"dark"}
# Evaluated as: not (5 > 2)
not 5 > 2 # False
# Evaluated as: (not True) and False
not True and False # False
```
Tired of Poor Python Skills? Fix That With Deep Grasping!
Learn More
