Is there something like js hoisting for class definitions in python?

Question

I've got 2 class definitions:

class Foo:
  def __init__(self, bar: Bar):
    # some code

class Bar:
  def __init__(self, foo: Foo):
    # some more code

I want to specify the types of the arguments. When I try to run that code I get "using variable 'Bar' before assignment" error.

Is it possible to tell the interpreter that Bar is defined a few lines below?

No, there is no hoisting. However, for type annotations in older versions you can simply use a string, in newer versions, `from __future__ import annotations` which will give you the behavior of postponed evaluation of annotations. — juanpa.arrivillaga, Dec 09 '19 at 20:49

Iain Shelvington · Accepted Answer · 2019-12-09T20:44:37.920

4

If you are using Python version 3.7 or later you can add the following to the top of your file

from __future__ import annotations

edited Dec 09 '19 at 20:44

answered Dec 09 '19 at 20:41

Iain Shelvington

2

...and for prior versions, simply use a string with the class name. The 3rdy party tools that deal with annotations will handle that. – jsbueno Dec 09 '19 at 20:44

1 Answers1