Extending Types

• TypeView subscripting can be used to set attributes on type objects, including built-in types.

• The impl() decorator can implement the decorated method onto a type.

Using the impl() decorator

Works for normal methods, dunder methods, or decorated static / class / property methods.

from einspect import impl

@impl(int)
def is_even(self):
    return self % 2 == 0

print((2).is_even())  # True

@impl(int)
def __matmul__(self, other):
    return self * other

print(5 @ 3)  # 15

@impl(int)
@property
def real(self):
    return self + 1

print((2).real)  # 3

@impl(int)
@classmethod
def try_from(cls, x):
    try:
        return cls(x)
    except ValueError:
        return None

print(int.try_from('2'))  # 2
print(int.try_from('a'))  # None

@impl(list)
@staticmethod
def abc():
    return "abc"

print(list.abc())  # "abc"
print([].abc())  # "abc"

Using orig to get original attributes

Sometimes you may want to defer to the original implementation of a method or attribute before it was overriden by impl or TypeView, in this case calling orig(<type>) will return a proxy object of the type where attribute access will yield original attributes.

For example, we want to override the __add__ of floats, by adding a print statement, but we want to still call the original __add__ after our print.

Calling orig(float) will give us the float proxy object, where orig(float).__add__ will give us the original float.__add__ method before our override.

from einspect import impl, orig

@impl(float)
def __add__(self, other):
    print(f"Adding {self} and {other}")
    return orig(float).__add__(self, other)

Using TypeView() subscripting

Views of types can be subscripted to either get or set attributes on the type. This works in all cases where @impl can be used.

In addition, this form can also set static attributes like __dict__ or __name__.

from einspect import view

v = view(int)
print(v["__name__"])  # int

v["is_even"] = lambda self: self % 2 == 0
print((2).is_even())  # True

v["__name__"] = "MyInt"
print(int.__name__)  # MyInt
print(int)  # <class 'MyInt'>

Multiple attributes can be set together by passing multiple attribute names.

from einspect import view

v = view(str)
v["__truediv__", "__floordiv__"] = str.split

print("Hello, world!" / ", ")  # ['Hello', 'world!']
print("abc-xyz" // "-")        # ['abc', 'xyz']