html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/pull/2648#issuecomment-451632884,https://api.github.com/repos/pydata/xarray/issues/2648,451632884,MDEyOklzc3VlQ29tbWVudDQ1MTYzMjg4NA==,1217238,2019-01-05T06:46:52Z,2019-01-05T06:46:52Z,MEMBER,Thanks,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,396008054
https://github.com/pydata/xarray/pull/2648#issuecomment-451627231,https://api.github.com/repos/pydata/xarray/issues/2648,451627231,MDEyOklzc3VlQ29tbWVudDQ1MTYyNzIzMQ==,1217238,2019-01-05T04:37:10Z,2019-01-05T04:37:10Z,MEMBER,I just pushed a commit to your branch that should fix the string identity issue (by not defining the constant multiple times).,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,396008054
https://github.com/pydata/xarray/pull/2648#issuecomment-451592518,https://api.github.com/repos/pydata/xarray/issues/2648,451592518,MDEyOklzc3VlQ29tbWVudDQ1MTU5MjUxOA==,1217238,2019-01-04T22:51:24Z,2019-01-04T22:51:24Z,MEMBER,"> Is the following statement True or False: ""The user should be allowed to explicitly declare that they want the concatenation dimension to be inferred by passing a keyword argument"".

This statement is False, but it looks like we have a related bug: we really should be importing `_CONCAT_DIM_DEFAULT` from `xarray.core.combine`, because we use identity comparison in that module. Right now this only works by virtue of the accident that identical string literals points to the same variable in CPython.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,396008054
https://github.com/pydata/xarray/pull/2648#issuecomment-451581920,https://api.github.com/repos/pydata/xarray/issues/2648,451581920,MDEyOklzc3VlQ29tbWVudDQ1MTU4MTkyMA==,1217238,2019-01-04T22:03:51Z,2019-01-04T22:03:51Z,MEMBER,"> ok, so we use the ReprObject for the default, and then test if `concat_dim` is of type `ReprObject and then test its equivalance?

No, just check identity with the exact ReprObject used as the default value.

This is just a slightly more readable version of the common idiom of use `object()` as a default value, e.g., as shown here
http://effbot.org/zone/default-values.htm#what-to-do-instead","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,396008054
https://github.com/pydata/xarray/pull/2648#issuecomment-451578157,https://api.github.com/repos/pydata/xarray/issues/2648,451578157,MDEyOklzc3VlQ29tbWVudDQ1MTU3ODE1Nw==,1217238,2019-01-04T21:47:32Z,2019-01-04T21:47:32Z,MEMBER,"Yes, it would be better to use the custom ReprObject.

On Fri, Jan 4, 2019 at 1:42 PM Benjamin Root <notifications@github.com>
wrote:

> *@WeatherGod* commented on this pull request.
> ------------------------------
>
> In xarray/backends/api.py
> <https://github.com/pydata/xarray/pull/2648#discussion_r245428584>:
>
> > @@ -606,7 +606,7 @@ def open_mfdataset(paths, chunks=None, concat_dim=_CONCAT_DIM_DEFAULT,
>      # Coerce 1D input into ND to maintain backwards-compatible API until API
>      # for N-D combine decided
>      # (see https://github.com/pydata/xarray/pull/2553/#issuecomment-445892746)
> -    if concat_dim is None or concat_dim == _CONCAT_DIM_DEFAULT:
> +    if concat_dim is None or concat_dim is _CONCAT_DIM_DEFAULT:
>
> I guess what I am getting at is a matter of user-friendliness. A user
> looking up the call signature of this method will see the default as the
> string (and not an object), but, they'll never be able to explicitly force
> concat dimension inference, because passing the string themselves will not
> work (it'll be a different object).
>
> —
> You are receiving this because you commented.
> Reply to this email directly, view it on GitHub
> <https://github.com/pydata/xarray/pull/2648#discussion_r245428584>, or mute
> the thread
> <https://github.com/notifications/unsubscribe-auth/ABKS1ll3RBImsQ_AzjJbKMdgtHFILXdIks5u_8qwgaJpZM4ZqBxI>
> .
>
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,396008054