[Python-Dev] Which direction is UnTransform? (original) (raw)

[Python-Dev] Which direction is UnTransform? / Unicode is different

Walter Dörwald walter at livinglogic.de
Wed Nov 20 14:38:46 CET 2013

On 20.11.13 02:28, Jim J. Jewett wrote:

[...] Instead of relying on introspection of .decodesto and .encodesto, it would be useful to have charsetcodecs and tranformcodecs as entirely different modules, with their own separate registries. I will even note that the existing help(codecs) seems more appropriate for charsetcodecs than it does for the current conjoined module.

I don't understand how a registry of transformation functions would simplify code. Without the transform() method I would write:

>>> import binascii
>>> binascii.hexlify(b'foo')
b'666f6f'

With the transform() method I should be able to write:

>>> b'foo'.transform("hex")

However how does the hex transformer get registered in the registry? If the hex transformer is not part of the stdlib, there must be some code that does the registration, but to get that code to execute, I'd have to import a module, so we're back to square one, as I'd have to write:

>>> import hex_transformer
>>> b'foo'.transform("hex")

A way around this would be some kind of import magic, but is this really neccessary to be able to avoid one import statement?

Furthermore different transformation functions might have different additional options. Supporting those is simple when we have simple transformation functions: The functions has arguments, and those are documented where the function is documented. If we want to support custom options for the .transform() method, transform() would have to pass along *args, **kwargs to the underlying transformer. However this is difficult to document in a way that makes it easy to find which options exist for a particular transformer.

Servus, Walter

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