New issue 824: Field detection issue when recreating data objects https://bitbucket.org/yt_analysis/yt/issue/824/field-detection-issue-when-re... Nathan Goldbaum: I ran into this when using a notebook. I found that when I re-ran a cell that creates a data object and then calculates a derived quantity, I get a field detection error the *second* time I run the cell. The following script exposes the buggy behavior: http://paste.yt-project.org/show/4462/ When run using the current experimental bookmark I get the following output and traceback: ``` goldbaum at ROUS in ~ ○ python test.py [8.15217983473e+49 g, 0.833333333333 code_mass] Traceback (most recent call last): File "test.py", line 21, in <module> print ad.quantities.total_mass() File "/Users/goldbaum/Documents/yt-hg/yt/data_objects/derived_quantities.py", line 194, in __call__ rv = super(TotalMass, self).__call__(fields) File "/Users/goldbaum/Documents/yt-hg/yt/data_objects/derived_quantities.py", line 163, in __call__ rv = super(TotalQuantity, self).__call__(fields) File "/Users/goldbaum/Documents/yt-hg/yt/data_objects/derived_quantities.py", line 59, in __call__ sto.result = self.process_chunk(ds, *args, **kwargs) File "/Users/goldbaum/Documents/yt-hg/yt/data_objects/derived_quantities.py", line 169, in process_chunk for field in fields] File "/Users/goldbaum/Documents/yt-hg/yt/data_objects/data_containers.py", line 205, in __getitem__ f = self._determine_fields([key])[0] File "/Users/goldbaum/Documents/yt-hg/yt/data_objects/data_containers.py", line 464, in _determine_fields raise YTFieldTypeNotFound(ftype) yt.utilities.exceptions.YTFieldTypeNotFound: Could not find field 'all'. ```