[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On Fri, Jan 01, 2021 at 02:53:33PM -0500, Eric V. Smith wrote: > On 1/1/2021 2:00 PM, Jonathan Fine wrote: > > > >By the way, this surprised me. Would anyone like to explain this? > >    >>> id(f()), id(f()) > >    (139927013695536, 139927013695536) > > > id's are only unique while an object

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On Fri, Jan 01, 2021 at 11:42:12AM -0800, Brendan Barnwell wrote: > On 2020-12-31 21:34, Steven D'Aprano wrote: > >Is there something we can do to make it easier for people to deal with > >recursive data structures, like the list repr and deepcopy code does? Is > >there a pattern we can abstract

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

It might not be that surprising to use a list if you are already using that list to keep track of your position in the hierarchy. You can probably assume that most of the time the depth is fairly low so the cost of scanning is low enough that the cost of building and updating the set costs enough

[Python-ideas] Re: A PEP to encourage people to mind docstrings in stub files

How do we avoid having the docstrings in two places? Large communities (e.g. Jupyter notebook and IPython users) rely on docstrings available at runtime. There should be a tool to update the docstrings in stubs before I could recommend duplicating them there. Even for stubs corresponding to

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

Interesting to look at the code for some of this. list.repr and dict.repr seem to be taking the "construct a set of seen items" approach. Except it's not using a set of ids, it's doing a linear pass over a list of visited PyObjects each time (which seems somewhat surprising to me, though it's

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 1/1/2021 2:00 PM, Jonathan Fine wrote: By the way, this surprised me. Would anyone like to explain this?     >>> id(f()), id(f())     (139927013695536, 139927013695536) id's are only unique while an object exists. Here the object returned by the first call is discarded after its id is

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 2/01/21 6:14 am, Jeff Allen wrote: we may as well say that the required result takes the form of an iterable of the nodes, which may subsequently be iterated by a consumer. In general you need more than that, I think. If you're printing a representation of the graph, you want to know about

[Python-ideas] Re: (Off-topic) Different object, same id

On Sat, Jan 2, 2021 at 7:56 AM Jonathan Fine wrote: > > Bravo, Jeff. I couldn't have chosen a better example. > > However, I'd expect large ints to be stored in two parts. A (class, pointer) > pair which has fixed size. And memory referenced by the pointer, large enough > to store the value of

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 01/01/2021 19:36, Richard Damon wrote: On 1/1/21 2:00 PM, Jonathan Fine wrote: Hi Richard You wrote I believe that one solution to detecting the cycles is to create a set of the object IDs you have visited and started to print. If you come across an ID you have already seen,

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 01Jan2021 16:34, Steven D'Aprano wrote: >This isn't so much an idea for Python, as a request for ideas to solve a >problem in Python. > >Back in the early days of Python, printing recursive lists could crash >the interpreter: > >a = [1, 2, 3] >a.append(a) >print(a) > >If you try

[Python-ideas] Re: (Off-topic) Different object, same id

Bravo, Jeff. I couldn't have chosen a better example. However, I'd expect large ints to be stored in two parts. A (class, pointer) pair which has fixed size. And memory referenced by the pointer, large enough to store the value of the large int. However, that's part of the language

[Python-ideas] (Off-topic) Different object, same id

On 01/01/2021 19:00, Jonathan Fine wrote: By the way, this surprised me. Would anyone like to explain this?     >>> id(f()), id(f())     (139927013695536, 139927013695536) That made me think. The result of the first f() has gone out of scope by the time the second call, and so the id (that

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 2020-12-31 21:34, Steven D'Aprano wrote: Is there something we can do to make it easier for people to deal with recursive data structures, like the list repr and deepcopy code does? Is there a pattern we can abstract out and provide as a tool or recipe for people to use in their own code?

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 1/1/21 2:00 PM, Jonathan Fine wrote: > Hi Richard > > You wrote > > I believe that one solution to detecting the cycles is to create a set > of the object IDs you have visited and started to print. If you come > across an ID you have already seen, this point is in a cycle. Sets are

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

Hi Richard You wrote I believe that one solution to detecting the cycles is to create a set > of the object IDs you have visited and started to print. If you come > across an ID you have already seen, this point is in a cycle. Sets are > fairly compact and intentionally fast to search for an

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 1/1/21 12:14 PM, Jeff Allen wrote: > On 01/01/2021 14:50, Jonathan Fine wrote: >> ... >> To summarise, it's loops / cycles in the representation of the data >> that's the problem. ... . >> >> Final idea. Perhaps a tool to detect cycles in data might be a good idea. >> > Detecting cycles will

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 1/1/21 12:12 PM, Jonathan Fine wrote: > Hi Richard > > You suggested > > A very simple and in my mind reasonable use for this is to build a > representation of a graph, where each node is represented by a > list (or > some other collection), and the connections are denoted by

[Python-ideas] Re: Right way to dataclass -> dict conversion.

On Thu, Dec 31, 2020 at 4:29 PM Eric V. Smith wrote: > Eric: what do you think about adding a "shallow" (or "deep") flag to > dataclasses.asdict() > that would then upack only the top-level dataclass? > > Currently a deep copy is made: > Honestly, I'm a bit confused as to why arbitrary types

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

Hi Jeff > But you're right, that's a better word for discussing the problem. > Steven's problem data structures are cyclic graphs. I don't agree that such > structures are a sign one is doing something wrong (outside the naive > approach to printing them out). > Thank you for agreeing with me,

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

A variant of the problem is the "occurs check", used in theorem proving: https://en.wikipedia.org/wiki/Occurs_check Removing the occurs check reduces the cost of unifying two terms (t1, t2) from *O(size(t1) + size(t2))* to *O(min(size(t1), size(t2)))*, which is why Prolog implementations don't do

[Python-ideas] Standard tool for iterating over recursive data structures?

Hi Jeff You wrote: Detecting cycles will involve a lot of bikeshedding. (Sorry, couldn't > resist.) > Indeed. That really brought a smile to my face. Thank you. As I recall, bikeshedding is endless discussion (cycles again) of the COLOUR to paint the bikeshed. And in mathematics there's the

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 01/01/2021 14:50, Jonathan Fine wrote: ... To summarise, it's loops / cycles in the representation of the data that's the problem. ... . Final idea. Perhaps a tool to detect cycles in data might be a good idea. Detecting cycles will involve a lot of bikeshedding. (Sorry, couldn't

[Python-ideas] Re: Option to not raise if file does not exists for os.remove()?

On Tue, 29 Dec 2020 at 22:40, Eelke van den Bos wrote: > > Hi Sergio, > > The pathlib module includes this feature: > https://docs.python.org/3/library/pathlib.html#pathlib.Path.unlink > > Best, > > Eelke I add that it's quite common to skip FileNotFoundError in removing a file. I think it's the

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

Hi Richard You suggested A very simple and in my mind reasonable use for this is to build a > representation of a graph, where each node is represented by a list (or > some other collection), and the connections are denoted by adding to > that collection the nodes that are adjacent (or maybe a

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 1/1/21 9:50 AM, Jonathan Fine wrote: > Hi > > I'd say the problem isn't recursion. Here I'm using the definitions > given in: > https://en.wikipedia.org/wiki/Recursion > > https://www.cs.utah.edu/~germain/PPS/Topics/recursion.html >

[Python-ideas] Re: A PEP to encourage people to mind docstrings in stub files

Alexey Volobuev wrote: > Sometimes you have to put docstrings in stub files e.g. when using code > generation. In that case, stubs are the only place you can locate "objects" > to add docstrings to. > Thus it is frustrating to find that docstring-related software generally > tends to ignore the

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

Hi I'd say the problem isn't recursion. Here I'm using the definitions given in: https://en.wikipedia.org/wiki/Recursion https://www.cs.utah.edu/~germain/PPS/Topics/recursion.html Rather, it's that the data has a loop (or cycle) in it. A simple example of this is >>> x = [] >>>

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On Fri, Jan 1, 2021 at 2:21 PM Marco Sulla wrote: > On Fri, 1 Jan 2021 at 06:38, Steven D'Aprano wrote: > > Relevant: https://bugs.python.org/issue42801 > > Can't reproduce on the latest trunk (3.10). I get 1989 as a result. > There were a spate of bugs about this, and was fixed by

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On 2021-01-01 at 16:34:15 +1100, Steven D'Aprano wrote: > This isn't so much an idea for Python, as a request for ideas to solve a > problem in Python. [examples of recurive data snipped] > The built-ins handle these cases okay. Likewise the copy.deepcopy > function takes care to avoid

[Python-ideas] Re: Standard tool for iterating over recursive data structures?

On Fri, 1 Jan 2021 at 06:38, Steven D'Aprano wrote: > Relevant: https://bugs.python.org/issue42801 Can't reproduce on the latest trunk (3.10). I get 1989 as a result. ___ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email