Chris Angelico wrote:
> Allow me to rephrase what I think you're arguing here, and you can
> tell me if I'm close to the mark.
You close to the mark. :)
Chris Angelico wrote:
> Given an object of a custom class C, you can make it usable as "x, y,
> z = C()" or "f(*C())" or anything else by defining __iter__, and in
> all ways that object will be iterable, unpackable, etc.
Yes, the only small problem:
```
class MyClass:
def __iter__(self):
return self.items_for_iteration
def __unpack__(self):
return self.items_for_unpack
```
This is not hurt.
Chris Angelico wrote:
> Given the same object, how can you ensure that it can be used as
> "f(**C())"? What about in "{}.update(C())"? Or "dict(C())"? Is there a
> single well-defined protocol that allows you to make your object
> usable in all mapping-like contexts?
Look at the example:
```
seq = zip('abc', 'xyz')
d = {}
d.update(seq)
print(d)
# {'a': 'x', 'b': 'y', 'c': 'z'}
def f(**kwargs):
print(kwargs)
seq = zip('abc', 'xyz')
f(**seq)
# TypeError: f() argument after ** must be a mapping, not zip
```
`dict.update` does the job.
I think a single protocol is:
`x, y, z = C()`, `[i for i in C()]`, ... call `C.__iter__()`
`f(C())`: get C instance.
`f(*C())`: call `C.__unpack_args__(self) -> Iterator[Any]:`
`f(**C())`: call `C.__unpack_kwargs__(self) -> Iterator[Tuple[str, Any]]:`
_______________________________________________
Python-ideas mailing list -- [email protected]
To unsubscribe send an email to [email protected]
https://mail.python.org/mailman3/lists/python-ideas.python.org/
Message archived at
https://mail.python.org/archives/list/[email protected]/message/AFBMUM2R2PCR42LEIESBFU2C25APQVJI/
Code of Conduct: http://python.org/psf/codeofconduct/
