What's the best way to implement System.Decimal conversions? #2432

the problem

In our Python wrapper of a .NET library, we've struggled along with our users with issues related to locale settings and related System.Decimal conversions.

• Help! Converting Pandas DataFrame to iterable Quotes facioquo/stock-indicators-dotnet#1165
• System.FormatException: Input string was not in a correct format facioquo/stock-indicators-python#382
• decimal.InvalidOperation with small numbers facioquo/stock-indicators-python#385

We're fairly sure we simply don't understand the problem and potential solutions well enough, but have tried a few things that usually boil down to a rather expensive double conversion from a string value ... which smells really bad.

...
return CsDecimal.Parse(str(decimal), CsCultureInfo.InvariantCulture)

Aside from the overly complex need to wrangle with our own defensive code, we did expect to see some overhead costs when going back and forth between .NET and Python, but are seeing larger than expected performance loss, about 10x slower. I have a sneaking suspicion that this string conversion is the biggest contributor.

I see a few failed attempts for feature ideas and some comments about using existing codecs or some custom variants, but they seem to do the same double conversion through a string value. Even my conversation with ChatGPT seems to suggest it.

• What would it take to implement built-in conversion to and from System.Decimal? #2319
• Automatically convert python decimal to System.Decimal #1775
• RecursionError when substracting System Decimal from Python Decimal #2240

the question(s)

1. In our scenario, what's the best way to exchange values to/from a .NET DLL object with decimal properties in Python?
2. There were some mentions of available codecs, any recommendations for which one to use?

cc @LeeDongGeon1996