lmauricius / py-forward_decl

A simple module for supporting forward references

py-forward_decl

A simple module for supporting forward references

What are those?

Forward references are references to objects that haven't been assigned yet. The reference is declared as just a name of the variable that has been forward declared. Forward declaration is a concept in many programming languages that declares the existance of a variable or a function before its value has been defined.

Why tho?

In 99% of cases when you would think of using forward references there is a better way to do it in Python. This is for the other 1%. Like when you need to reference a class from deep within an expression inside a class variable inside that class' definition. Also useful for recursive parser production rules that are defined using Python's semantics.

Installation

Install it using pip:

pip install forward-decl

Usage

Basic example:

var2 = FwDecl()

var1 = OpaqueFwRef("var2")
var2 = "Hello"

print(var1.get_ref()) # prints 'Hello'

A more useful case:

MyClass = FwDecl()

class MyClass:
    clsReference = OpaqueFwRef("MyClass")
    clsVar = "Hello"

print(MyClass.clsReference.get_ref().clsVar) # prints 'Hello'