Python wish list

[bramcohen]

Now that the moratorium on Python language features is over, I'll put in my thoughts on what new stuff the language could use. I don't have much to suggest, and what I do have to suggest is fairly minor. This is because I'm happy with the language.

new on default parameters

One of the gotchas in python is that default parameters are reused, so if

Comments

[elsmi]

raw binary conversion -- do you mean struct, or something else?

[bramcohen]

struct does a reasonable approximation of what I want, but Yech.

[ext_439117]

It sounds like the struct module should do what you want for raw binary conversion.

Since the dictionary objects are only kept in the hash table and iteration just walks through that table looking for objects, there'd be no way to scramble the contents in-place. Objects can only be in one place for a given hash value. You'd have to implement this by iterating the dictionary into a list and shuffling that list in place (like random.shuffle does), so you might as well do it yourself.

^ on bytes is an obvious feature, though, you're absolutely right. I might actually write a patch for that myself...

[bramcohen]

Just changing the hash function which dicts use should scramble things well enough.

Does struct work on arbitrary size integers and allow completely cross-platform operation? The documentation is less than ideal.

[manuzhai]

The table for the format characters seems clear enough?

[bramcohen]

Until you've gone through some examples, it's very opaque, and it really, really, would be nice if it clarified whether int sizes might be different on different platforms.

dictionary scrambling

[manuzhai]

Actually it's not the dict that defines the hashing method, it's the __hash__() method of the class of the objects used as keys. So you could probably handle this in your own code by setting the __class__ of the keys to a subclass of their actual __class__, plus a changed __hash__ method?

Re: dictionary scrambling

[bramcohen]

Yeah, I could do something like that, but that would involve extensive ugly changes to my code, when it should just be a single call to the stdlib.

[ciphergoth]

I don't understand the semantics of your proposed "eggs = new []". If it's "eggs = new list" I understand them.

[bramcohen]

Saying [] is how you instantiate a new list in Python. It's very non-idiomatic to say list() (although I tried it now and that does work).

[ciphergoth]

Right, but [] is a list, where as "list" is a function that returns a new list every time you call it. Though I guess "new" could act like "lambda" wrt whatever was on its right.

[bramcohen]

Yeah, it's sort of acting like a lambda, but you could put an actual lambda there and it would result in the parameter being a function, which is not what you want. Other values should work as well, for example

def spam(eggs = new {3: ['a', 'b', 'c']})

[ciphergoth]

WRT dictionary scrambling: maybe what you need is a way to arrange for your own class to take the place of "dict"?

[bramcohen]

Yes, but that would involve extensive changes to my whole codebase for what should be a single call.

[ciphergoth]

No, I mean a way for Python to use your class whenever you refer to "dict" or {} or similar.

[bramcohen]

I don't think it has that functionality, not so much monkey patching in Python.