6.15. Operator Builtin

• abs()

• bool()

• complex()

• del()

• delattr()

• dir()

• divmod()

• float()

• getattr()

• hash()

• hex()

• int()

• iter()

• len()

• next()

• oct()

• pow()

• reversed()

• round()

• setattr()

6.15.1. About

Table 6.11. Builtin Functions Overload

Function	Method
abs(obj)	obj.__abs__()
bool(obj)	obj.__bool__()
complex(obj)	obj.__complex__()
del obj	obj.__del__()
delattr(obj, name)	obj.__delattr__(name)
dir(obj)	obj.__dir__()
divmod(obj, other)	obj.__divmod__(other)
float(obj)	obj.__float__()
getattr(obj, name, default)	obj.__getattr__(name, default)
hash(obj)	obj.__hash__()
hex(obj)	obj.__hex__()
int(obj)	obj.__int__()
iter(obj)	obj.__iter__()
len(obj)	obj.__len__()
next(obj)	obj.__next__()
oct(obj)	obj.__oct__()
pow(obj)	obj.__pow__()
reversed(obj)	obj.__reversed__()
round(obj, ndigits)	obj.__round__(ndigits)
setattr(obj, name)	obj.__setattr__(name)

6.15.2. Length

>>> data = [1, 2, 3]
>>>
>>> len(data)
3
>>>
>>> data.__len__()
3

This is because len(data) calls data.__len__().

>>> class Astronaut:
...     pass
...
>>>
>>> a = Astronaut()
>>>
>>> len(a)
Traceback (most recent call last):
TypeError: object of type 'Astronaut' has no len()

>>> class Astronaut:
...     def __len__(self):
...         return 69
>>>
>>>
>>> a = Astronaut()
>>>
>>> len(a)
69

6.15.3. Float

>>> class Astronaut:
...     pass
...
>>>
>>> a = Astronaut()
>>>
>>> float(a)
Traceback (most recent call last):
TypeError: float() argument must be a string or a real number, not 'Astronaut'

>>> class Astronaut:
...     def __float__(self):
...         return 13.37
...
>>>
>>> a = Astronaut()
>>>
>>> float(a)
13.37

6.15.4. Abs

>>> from math import sqrt
>>> from dataclasses import dataclass
>>>
>>>
>>> @dataclass
... class Vector:
...     x: int = 0
...     y: int = 0
...
...     def __abs__(self):
...         return sqrt(self.x**2 + self.y**2)
>>>
>>>
>>> abs(Vector(x=3, y=4))
5.0

6.15.5. Round

>>> pi = 3.1415
>>>
>>> type(pi)
<class 'float'>
>>>
>>> round(pi, 2)
3.14
>>>
>>> float.__round__(pi, 2)
3.14

6.15.6. Use Case - 0x01

>>> class Astronaut:
...     def __float__(self) -> float:
...         return 1961.0
...
...     def __int__(self) -> int:
...         return 1969
...
...     def __len__(self) -> int:
...         return 170
...
...     def __str__(self) -> str:
...         return 'My name... José Jiménez'
...
...     def __repr__(self) -> str:
...         return f'Astronaut()'
>>>
>>>
>>> astro = Astronaut()
>>>
>>> float(astro)
1961.0
>>>
>>> int(astro)
1969
>>>
>>> len(astro)
170
>>>
>>> repr(astro)
'Astronaut()'
>>>
>>> str(astro)
'My name... José Jiménez'
>>>
>>> print(astro)
My name... José Jiménez