7.14. Operator Builtin

  • abs()

  • bool()

  • complex()

  • del()

  • delattr()

  • dir()

  • divmod()

  • float()

  • getattr()

  • hash()

  • hex()

  • int()

  • iter()

  • len()

  • next()

  • oct()

  • pow()

  • reversed()

  • round()

  • setattr()

7.14.1. About

Table 7.8. 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)

7.14.2. Length

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

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

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

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

7.14.3. Float

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

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

7.14.4. 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

7.14.5. Round

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

7.14.6. Use Case - 0x01

>>> class User:
...     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'User()'
>>>
>>>
>>> mark = User()
>>>
>>> float(mark)
1961.0
>>>
>>> int(mark)
1969
>>>
>>> len(mark)
170
>>>
>>> repr(mark)
'User()'
>>>
>>> str(mark)
'My name... José Jiménez'
>>>
>>> print(mark)
My name... José Jiménez