Issue 36401: Readonly properties should be marked as such in help() (original) (raw)

Created on 2019-03-22 23:17 by rhettinger, last changed 2022-04-11 14:59 by admin. This issue is now closed.

| Messages (6) | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------- | ---------------------- | -------------------------------------------------------------- | ----------------------------------------------------------- | | -------------------------------------------------------------- | ---------------------------------------------------------- | | --------------------------------------------------------------- | ------------------------------------------------------------- | ------------------------------------------------------- | ------------------------ | --------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------- | | --------------------------------- | | --------------------- | | ---------------------------------- | ----------- | | ---------------------------------------------------------------------- | --------------------------- | | ------------------------ | ------------------- | | ---------------------------------------------------------------------- | ---------------------------- | | ----- | ------------------- | | ---------------------------------------------------------------------- | ---------------------------------------------------------- | | --- | -------------- | | ---------------------------------------------------------------------- | ---------------------------------------------------------------------- | | ----- | ----------------- | | msg338621 - (view) | Author: Raymond Hettinger (rhettinger) * | Date: 2019-03-22 23:17 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | It is common to create read-only properties with the '@property' decoration but the existing help() output doesn't annotate them as such. One way to go is to annotate each one separately: | ---------------------------------------------------------------------- | Data descriptors inherited from _IPAddressBase: | | compressed (read-only property) <== NEW ANNOTATION | Return the shorthand version of the IP address as a string. | | exploded (read-only property) <== NEW ANNOTATION | Return the longhand version of the IP address as a string. | | reverse_pointer (read-only property) <== NEW ANNOTATION | The name of the reverse DNS pointer for the IP address, e.g.: | >>> ipaddress.ip_address("127.0.0.1").reverse_pointer | '1.0.0.127.in-addr.arpa' | >>> ipaddress.ip_address("2001:db8::1").reverse_pointer | '1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2.ip6.arpa' Another way to go is to break the data descriptor section into two sections --- isolate those that define __set__ or __delete__ from those that don't. For example, given this code: class A: 'Variety of descriptors and method' __slots__ = '_w', '_x' def __init__(self, w: int, x: str): 'initializer' self.w = w self.x = x @classmethod def cm(cls, u): 'do something with u' return cls(u * 4) @staticmethod def sm(v): 'do something with v' return v * 3 @property def rop(self): 'computed field' return self._w * 2 @property def wandr(self): 'managed attribute' return self._w @wandr.setter def wandr(self, w): self._w = w Produce this help output: Help on class A in module __main__: class A(builtins.object) | A(w: int, x: str) | | Variety of descriptors and method | | Methods defined here: | | __init__(self, w: int, x: str) | initializer | | ---------------------------------------------------------------------- | Class methods defined here: | | cm(u) from builtins.type | do something with u | | ---------------------------------------------------------------------- | Static methods defined here: | | sm(v) | do something with v | | ---------------------------------------------------------------------- | Read-only descriptors defined here: <== NEW HEADING | | rop | computed field | | ---------------------------------------------------------------------- | Mutable data descriptors defined here: <== NEW HEADING AND SECTION | | wandr | managed attribute | | msg338627 - (view) | Author: Raymond Hettinger (rhettinger) * | Date: 2019-03-22 23:33 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For property objects, we have to look at *fset* and *fdel* to find-out whether they are assignable: >>> A.rop.fset is None True >>> A.wandr.fset is None False | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | msg338628 - (view) | Author: Stéphane Wirtel (matrixise) * | Date: 2019-03-23 00:00 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | @Raymond +1 but can we do the same thing with the PyGetSetDef declaration for the C Part? | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | msg338639 - (view) | Author: Raymond Hettinger (rhettinger) * | Date: 2019-03-23 01:14 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | > but can we do the same thing with the PyGetSetDef declaration > for the C Part? The would likely take an API change. For now, using only what is already exposed in Python, we can only partition data descriptors in two groups: * Known to be readonly because __set__ is missing or fset is None * Possibly writeable, can't really tell until __set__ is called Example in the latter category, >>> t = time.localtime() >>> hasattr(type(t).tm_sec, '__set__') True >>> t.tm_sec = 31 Traceback (most recent call last): File "<pyshell#23>", line 1, in t.tm_sec = 31 AttributeError: readonly attribute | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | msg338773 - (view) | Author: Raymond Hettinger (rhettinger) * | Date: 2019-03-25 00:07 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | New changeset 62be33870e2f8517314bf9c7275548e799296f7e by Raymond Hettinger in branch 'master': bpo-36401: Have help() show readonly properties separately (GH-12517) https://github.com/python/cpython/commit/62be33870e2f8517314bf9c7275548e799296f7e | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | msg338781 - (view) | Author: Stéphane Wirtel (matrixise) * | Date: 2019-03-25 05:18 | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Hi Raymond, About the C API, I wanted to know that because I started to use neovim for the development of CPython mix between C and Python is really great with this tool. Also, I wanted to have the description of the C parts, example, when I have PyArg_ParseTupleAndKeywords under the cursor, with (n)vim I could use the K shortcut and see the description of this function via the keywordprg of vim. But we have the result from Sphinx, because the C part is described in the .rst files. So, maybe I could develop a wrapper for Sphinx and the manpages. So, thank you for your PR. | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |