NorthGuard / observable_primitives

Implements emulations of python primitives, which are observable (notifies observers) when using augmented arithmetic (ex. +=, -=, etc.).

observable_primitives

Implements emulations of python primitives, which are observable (notifies observers) when using augmented arithmetic (ex. +=, -=, etc.).

For example ObservableInteger can be used exactly as a normal integer. All arithmetics are performed as expected of an integer (+, -, divmod(), //, str(), repr() etc.). If any of the augmented arithmetics are called, updating the value of the integer, then all observers are notified (+=, -=, *=, //= etc.).

The available observables are:

• ObservableInteger
• ObservableBool
• ObservableFloat
• ObservableComplex

Basic usage

from observable_primitives import ObservableInteger, NumericPrintObserver

# Make an observable primitive (initialized at 10)
obs_int = ObservableInteger(val=10)

# Make observer (simply prints notified changes)
observer = NumericPrintObserver(obs_int)

# Operations which observer is not notified of
print(obs_int)
print(2 + obs_int)
print(obs_int * 3)
print(obs_int // 3)
print(obs_int / 3)
print(obs_int % 3)
# 10
# 12
# 30
# 3
# 3.3333333333333335
# 1

# Change value of observable. This notifies observer which prints notification.
obs_int += 3
obs_int *= 5
# NumericPrintObserver(10 __iadd__ 3 = 13)
# NumericPrintObserver(13 __imul__ 5 = 65)

print(obs_int)
# 65

Implementing Observers

Custom-made observers can be made by subclassing Observer and implementing the observe-method with signature:

observe(self, *args, **kwargs)

For ObservableInteger, ObservableBool, ObservableFloat and ObservableComplex, the arguments passed on to observe are:

args = []
kwargs = {
    'previous': PPP,
    'method': MMM,
    'other': OOO,
    'new_val': NNN
}

Where PPP is the value the observable had before the operation, MMM is the name of the invoked operation (ex. __iadd__), OOO is the other value use in the operation (ex. adding 4 to an integer) and NNN is the value of the observable after the operation.