Increment ++ & Decrement -- Operators In Pure Python

incdec.py

class IncDec:
    # TODO(pbz): Extend this so that all math ops
    # TODO work seamlessly to return the inner type
    # TODO so that it doesn't break anything
    def __init__(self, value=None):
        self.value = value
    def __pos__(self):
        return self.value + 1
    def __neg__(self):
        return self.value - 1
    def __str__(self):
        return f'Inc({self.value})'

class Foo:
    def __init__(self, value):
        self.value = value
    def __add__(self, other):  # This is what makes -- and ++ useful
        return Foo(self.value + other)
    def __sub__(self, other):
        return Foo(self.value - other)
    def __pos__(self):
        return IncDec(self.value)
    def __neg__(self):
        return IncDec(self.value)
    
a = Foo(1)
print(++a)  # 2
print(--a)  # 0