Add type hints for ecosystem

[janga1997]

Fixes part of #808
I have no idea what type of a variable fitness is. Could someone help out?

[drvinceknight]

Hi @janga1997, thanks for working on this.

I have no idea what type of a variable fitness is. Could someone help out?

The type is types.FunctionType. Let me know if I can assist more.

[janga1997]

@drvinceknight In this case, can we go along with types.LambdaType?
And what is results? I assume it is an instance? (types.InstanceType)

[drvinceknight]

@drvinceknight In this case, can we go along with types.LambdaType?

types.FunctionType is better as it allows users to pass functions that were not defined as lambda functions.

And what is results? I assume it is an instance? (types.InstanceType)

In [14]: >>> import axelrod as axl
    ...: >>> players = (axl.Cooperator(), axl.Alternator(), axl.TitForTat())
    ...: >>> tournament = axl.Tournament(players)
    ...: >>> results = tournament.play()
    ...: 
                                                                                                                                                      
In [15]: type(results)
Out[15]: axelrod.result_set.ResultSetFromFile

Although ideally the type of results should be axelrod.result_set.ResultSet. ResultSetFromFile inherits from ResultSet. However:

In [18]: type(results) is axl.result_set.ResultSet
Out[18]: False

In [19]: type(results) is axl.result_set.ResultSetFromFile
Out[19]: True

So that might need something...

[janga1997]

@drvinceknight I kinda understand what the problem is, but I don't know the solution to it.
Should I keep it as axl.result_set.ResultSetFromFile for now?

[drvinceknight]

@drvinceknight I kinda understand what the problem is, but I don't know the solution to it.

I'm not entirely sure what the solution is either (@marcharper, @Nikoleta-v3 ?).

Should I keep it as axl.result_set.ResultSetFromFile for now?

I don't see why not.

[janga1997]

@drvinceknight I facing some trouble with the type of results? Would you mind?
Should I do an import axelrod first?

[drvinceknight]

Should I do an import axelrod first?

Yup, you'll need to do that. :)

[janga1997]

@drvinceknight Is it okay for a merge now?

[drvinceknight]

@drvinceknight Is it okay for a merge now?

It looks good to me. We have a two core reviewer policy on all PRs so someone else will be around to make sure I haven't missed anything (or if they see the way to get around the ResultSet/ResultSetFromFile issue :)). 👍

[marcharper]

Is it always a results set from a file?

[janga1997]

@marcharper not sure. I faced this issue when adding type hints for derived classes of Player such as TitforTat, etc too.
We need a way to check if the object is an instance of the parent class ,and not the derived. How, I can't figure out.

[marcharper]

According to the docs it looks like a subclass will type check as valid if a parent class is expected. Let's test for the parent type if multiple possible derived types are possible.

[janga1997]

@marcharper just to be sure, I use ResultSet for results, and Player for any kind of player, and so on?

[marcharper]

Unless you know for sure that something more specific is appropriate. Also please try to run mypy on the files you annotate:
mypy --ignore-missing-imports --follow-imports skip axelrod/actions.py

You may get some errors until #837 is merged (you can rebase if you know how to do that).

[marcharper]

Type checker says:

axelrod/ecosystem.py:10: error: The return type of "__init__" must be None
axelrod/ecosystem.py:40: error: Incompatible types in assignment (expression has type Callable[[Any], Any], variable has type "MethodType")
axelrod/ecosystem.py:61: error: Unsupported operand types for + ("int" and "float")
axelrod/ecosystem.py:61: error: No overload variant of "__setitem__" of "list" matches argument types [builtins.int*, builtins.float]

Let us know if you need help (and feel free to join the gitter chat to ask questions).

[janga1997]

@marcharper The remaining errors seem to be from this line payoffs[ip] += p * pops[jp].
But I guess python typecasts int to float anyway? Is it a serious issue?

[marcharper]

Try a float -- there's no reason to force an integer here -- and see if it works. Otherwise let's use Union[float, int] or some kind of generic numeric type (if that's a thing in Python 3.5).

[janga1997]

@drvinceknight There is still one error remaining,
axelrod/ecosystem.py:40: error: Incompatible types in assignment (expression has type Callable[[Any], Any], variable has type "MethodType")

for the line
self.fitness = lambda p: p. We assigned FunctionType to fitness

[drvinceknight]

@drvinceknight There is still one error remaining,
axelrod/ecosystem.py:40: error: Incompatible types in assignment (expression has type Callable[[Any], Any], variable has type "MethodType")

for the line
self.fitness = lambda p: p. We assigned FunctionType to fitness

It looks like a Callable type will do the trick:

4 from types import Callable 
...
10     def __init__(self, results: ResultSet, fitness: Callable, ...

[janga1997]

@drvinceknight Yeah, but didn't we decide upon FunctionType? Why are we doing Callable now?
I don't get it.

[drvinceknight]

@drvinceknight Yeah, but didn't we decide upon FunctionType? Why are we doing Callable now?

I think my original advice on the use of FunctionType was too restrictive. Here's more information about the Callable type here: https://docs.python.org/3/library/typing.html#typing.Callable

https://docs.python.org/3/library/typing.html#typing.Callable

An in fact I think it should actually be:

 def __init__(self, results: ResultSet, fitness: Callable[[float], float], ...

which indicates that it's a callable that takes a float and returns a float.

[drvinceknight]

Apologies, it should be:

4 from typing import Callable 

[drvinceknight]

This looks fine to me now. 👍