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Implement IConvertible on PyObject by filmor · Pull Request #1762 · pythonnet/pythonnet · GitHub
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Implement IConvertible on PyObject #1762

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Merged
lostmsu merged 1 commit into from
Apr 11, 2022
Merged

Implement IConvertible on PyObject #1762

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Implement IConvertible interface on PyObject
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@filmor
filmor committed Apr 10, 2022
commit 9a0ceb698ea83ef726e52e84849ff62c6f5ef053
2 changes: 1 addition & 1 deletion src/runtime/Converter.cs
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Expand Up @@ -550,7 +550,7 @@ internal static int ToInt32(BorrowedReference value)
/// <summary>
/// Convert a Python value to an instance of a primitive managed type.
/// </summary>
private static bool ToPrimitive(BorrowedReference value, Type obType, out object? result, bool setError)
internal static bool ToPrimitive(BorrowedReference value, Type obType, out object? result, bool setError)
{
result = null;
if (obType.IsEnum)
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2 changes: 2 additions & 0 deletions src/runtime/PythonTypes/PyFloat.cs
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Expand Up @@ -101,5 +101,7 @@ public static PyFloat AsFloat(PyObject value)
PythonException.ThrowIfIsNull(op);
return new PyFloat(op.Steal());
}

public override TypeCode GetTypeCode() => TypeCode.Double;
}
}
2 changes: 2 additions & 0 deletions src/runtime/PythonTypes/PyInt.cs
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Expand Up @@ -230,5 +230,7 @@ public string ToString(string format, IFormatProvider formatProvider)
using var _ = Py.GIL();
return ToBigInteger().ToString(format, formatProvider);
}

public override TypeCode GetTypeCode() => TypeCode.Int64;

@lostmsu lostmsu Apr 10, 2022

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Generally, this is wrong.

@filmor filmor Apr 10, 2022

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The docs are a bit unclear on this function. I used this as an "should almost always work" value, the InvalidCastException might still be thrown if the conversion fails. We could drop the GetTypeCode overrides entirely and just return TypeCode.Object if you'd prefer that.

@lostmsu lostmsu Apr 10, 2022 •
edited
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I can't say for others, just for this one. Honestly, not sure if anyone ever uses this. Our own code assumes TypeCode.Int64 refers to System.Int64, so removing might be a good idea.

@filmor filmor Apr 10, 2022

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I'm not sure I follow. GetTypeCode is supposed to be a hint that allows you to write a switch like

switch (convertible.GetTypeCode()) {
    case TypeCode.Int64:
        return Convert.ToInt64(convertible);
}

It doesn't mean that the object is a System.Int64 already.

@lostmsu lostmsu Apr 10, 2022 •
edited
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You seem to be correct on that. Still not sure Int64 is valid for this specific case, but float and string probably are. I am fine either way though. I don't think we will get people complaining about this returning Int64 any time soon.

}
}
53 changes: 53 additions & 0 deletions src/runtime/PythonTypes/PyObject.IConvertible.cs
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@@ -0,0 +1,53 @@
using System;

namespace Python.Runtime;

public partial class PyObject : IConvertible
{
public virtual TypeCode GetTypeCode() => TypeCode.Object;

private T DoConvert<T>()
{
using var _ = Py.GIL();
if (Converter.ToPrimitive(Reference, typeof(T), out object? result, setError: false))
{
return (T)result!;
}
else
{
throw new InvalidCastException();
}
}

public bool ToBoolean(IFormatProvider provider) => DoConvert<bool>();
public byte ToByte(IFormatProvider provider) => DoConvert<byte>();
public char ToChar(IFormatProvider provider) => DoConvert<char>();
public short ToInt16(IFormatProvider provider) => DoConvert<short>();
public int ToInt32(IFormatProvider provider) => DoConvert<int>();
public long ToInt64(IFormatProvider provider) => DoConvert<long>();
public sbyte ToSByte(IFormatProvider provider) => DoConvert<sbyte>();
public ushort ToUInt16(IFormatProvider provider) => DoConvert<ushort>();
public uint ToUInt32(IFormatProvider provider) => DoConvert<uint>();
public ulong ToUInt64(IFormatProvider provider) => DoConvert<ulong>();

public float ToSingle(IFormatProvider provider) => DoConvert<float>();
public double ToDouble(IFormatProvider provider) => DoConvert<double>();

public string ToString(IFormatProvider provider) => DoConvert<string>();

public DateTime ToDateTime(IFormatProvider provider) => throw new InvalidCastException();
public decimal ToDecimal(IFormatProvider provider) => throw new InvalidCastException();

public object ToType(Type conversionType, IFormatProvider provider)
{
if (Converter.ToManaged(Reference, conversionType, out object? result, setError: false))
{
return result!;
}
else
{
throw new InvalidCastException();
}
}

}
2 changes: 2 additions & 0 deletions src/runtime/PythonTypes/PyString.cs
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Expand Up @@ -59,5 +59,7 @@ public static bool IsStringType(PyObject value)
{
return Runtime.PyString_Check(value.obj);
}

public override TypeCode GetTypeCode() => TypeCode.String;
}
}
7 changes: 7 additions & 0 deletions tests/test_conversion.py
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Expand Up @@ -670,3 +670,10 @@ def test_int_param_resolution_required():
data = list(mri.MethodA(0x100000000, 10))
assert len(data) == 10
assert data[0] == 0

def test_iconvertible_conversion():
change_type = System.Convert.ChangeType

assert 1024 == change_type(1024, System.Int32)
assert 1024 == change_type(1024, System.Int64)
assert 1024 == change_type(1024, System.Int16)