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Provide hook to implement __repr__ #808

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Merged
filmor merged 17 commits into from
Oct 18, 2019
Merged

Provide hook to implement __repr__ #808

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351d9ff
Provide hook to implement __repr__
koubaa Jan 20, 2019
d71a391
Merge branch 'master' into repr
filmor Mar 6, 2019
2a002d7
fix casing
koubaa Mar 8, 2019
cf1f1dc
Merge branch 'master' into repr
filmor Mar 19, 2019
1c0984f
Merge branch 'master' into repr
koubaa Apr 5, 2019
a5b245b
Merge branch 'master' into repr
filmor Apr 7, 2019
82aea1f
Merge branch 'master' into repr
filmor Apr 8, 2019
502f0c3
Merge branch 'master' into repr
filmor Jun 20, 2019
eb4004a
Merge branch 'master' into repr
filmor Aug 2, 2019
c6ae6a4
Merge branch 'master' into repr
filmor Sep 12, 2019
0916406
update based on review
koubaa Sep 15, 2019
2fb6a43
fix whitespace
koubaa Sep 15, 2019
9fc5b5f
fix whitespace
koubaa Sep 15, 2019
00b55db
fix
koubaa Sep 15, 2019
accc797
Don't use repr in __str__. Clean up unneeded tests
koubaa Oct 16, 2019
ff5d96c
fix leak
koubaa Oct 16, 2019
264c78b
Merge branch 'master' into repr
koubaa Oct 16, 2019
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fix whitespace
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@koubaa
koubaa committed Sep 15, 2019
commit 2fb6a430a0eb4f271cfdc9229bbe55ac8bc5b85e
10 changes: 5 additions & 5 deletions src/runtime/classbase.cs
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Expand Up @@ -242,12 +242,12 @@ public static IntPtr tp_str(IntPtr ob)

//First check which type in the object hierarchy provides ToString()
//ToString has two "official" overloads so loop over GetMethods to get the one without parameters
var method = type.GetMethod("ToString", new Type[]{});
if (method.DeclaringTyppe != typeof(object))
{
var method = type.GetMethod("ToString", new Type[]{});
if (method.DeclaringTyppe != typeof(object))
{
//match! something other than object provides a parameter-less overload of ToString
return Runtime.Pystring_FromString(co.inst.ToString());
}
return Runtime.Pystring_FromString(co.inst.ToString());
}

//If the object defines __repr__, call it.
System.Reflection.MethodInfo reprMethodInfo = instType.GetMethod("__repr__");
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@lostmsu lostmsu Sep 12, 2019 •
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Since all .NET types have ToString, why does it even try __repr__? If somebody really needs it, they can do override string ToString() => __repr__()

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@filmor filmor Sep 14, 2019

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That's not the same, though. ToString is more akin to __str__, there is no real equivalent to __repr__ in .NET.

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@lostmsu lostmsu Sep 14, 2019

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Yeah, this is the tp_str implementation. tp_repr is below

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@koubaa koubaa Sep 15, 2019

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@lostmsu See the comment:
//The return value must be a string object. If a class defines repr() but not str(),
//then repr() is also used when an “informal” string representation of instances of that
//class is required.

This sentence comes straight from the python manual, I didn't make it up

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@lostmsu lostmsu Sep 16, 2019

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@koubaa the default inheritance hierarchy for C# classes from Python's point of view is Python's object <- System.Object <- CustomCSharpClass.

Since for all .NET classes overriding ToString is how you implement __str__, I don't see why it should be different for System.Object. Hence I think .NET classes should just always call ToString for tp_str.

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@koubaa koubaa Sep 16, 2019 •
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@lostmsu I took a look. I agree some kind of consensus between interface vs reflection for dunder methods should be reached and applied throughout the code base. One argument for reflection is that you can use extension methods to add these. If I take an existing C# codebase and write some extension methods in a separate assembly, I can provide __repr__ and __getattr__ to it. What do you think?

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@lostmsu lostmsu Sep 16, 2019

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@koubaa, extension methods would be hard to find. You'd have to enumerate all types in all assemblies. GetMethods won't return them.

In addition to that, what would be the semantics of multiple assemblies defining an extension method with the same signature?

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@koubaa koubaa Sep 17, 2019

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@lostmsu ah, didn't know that.

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@koubaa koubaa Sep 18, 2019

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@lostmsu I am still not convinced about the interface approach. It would require a hard build dependency on C# libraries onto PythonNet. It seems like a tough sell for some of the mature C# libraries out there.

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@koubaa koubaa Oct 16, 2019

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@lostmsu I changed this as you requested. I don't think I can capture the repr function in a Func object since this is a static method.

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