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/5680#issuecomment-895508489,https://api.github.com/repos/pydata/xarray/issues/5680,895508489,IC_kwDOAMm_X841YGAJ,1217238,2021-08-09T20:11:24Z,2021-08-09T20:11:24Z,MEMBER,"To follow up, from a _practical_ perspective, there are two problems with assuming that there are always ""truly missing values"" (case 2):

1. It makes it impossible to represent the full range of values in a data type, e.g., 255 for uint8 now means ""missing"".
2. Due to unfortunately limited options for representing missing data in NumPy, Xarray represents truly missing values in its data model with ""NaN"". This is more or less OK for floating point data, but means that integer data gets converted into floats. For example, uint8 would now get automatically converted into float32.

Both of these issues are problematic for faithful ""round tripping"" of Xarray data into netCDF and back. For this reason, Xarray needs an unambiguous way to know if a netCDF variable could contain semantically missing values. So far, we've used the presence of `missing_value` and `_FillValue` attributes for that.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,963006707
https://github.com/pydata/xarray/pull/5680#issuecomment-895455163,https://api.github.com/repos/pydata/xarray/issues/5680,895455163,IC_kwDOAMm_X841X4-7,1217238,2021-08-09T18:46:59Z,2021-08-09T18:46:59Z,MEMBER,"Right, so netCDF3 has a default value used for filling out variables before any data is written.

My concern is that there are two (overlapping) use-case for fill values:

1. The default array value used for variables on disk, e.g., before they are written
2. Truly missing values (with different semantics), which Xarray represents with NaN

Certainly these _sometimes_ coincide, but that isn't necessarily the case.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,963006707
https://github.com/pydata/xarray/pull/5680#issuecomment-895022291,https://api.github.com/repos/pydata/xarray/issues/5680,895022291,IC_kwDOAMm_X841WPTT,1217238,2021-08-09T07:54:22Z,2021-08-09T07:54:22Z,MEMBER,"Could you clarify where these default fill values come from?

Are they just an arbitrary choice by netCDF4-Python? Or are they part of some broader standard?","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,963006707