pd.dataframe.at won't work in modin

[cinnqi]

System information

• OS Platform and Distribution (e.g., Linux Ubuntu 16.04): Linux
• Modin version (modin.__version__):0.13
• Python version:3.8
• Code we can use to reproduce:

Describe the problem

I am trying to insert an object into a cell of data frame, by using pd.dataframe.at(index,'row', object).
it works in pandas but not in modin.

Source code / logs

File "compare_modin.py", line 98, in
df_record.loc[i,'mainsnaks'] = mainsnaks
File "/home/chengxi/.local/lib/python3.8/site-packages/modin/pandas/indexing.py", line 742, in setitem
super(_LocIndexer, self).setitem(
File "/home/chengxi/.local/lib/python3.8/site-packages/modin/pandas/indexing.py", line 412, in setitem
item = self._broadcast_item(row_lookup, col_lookup, item, to_shape)
File "/home/chengxi/.local/lib/python3.8/site-packages/modin/pandas/indexing.py", line 475, in _broadcast_item
raise ValueError(
ValueError: could not broadcast input array from shape (631,) into shape (1, 1)

[devin-petersohn]

Hi @cinnqi thanks for reporting!

It looks like the error happens at loc instead of at (although they are quite similar). In this line:

df_record.loc[i,'mainsnaks'] = mainsnaks

What is i and mainsnaks? It looks like i is a row label (maybe an integer) and mainsnaks is a 1D Series or array. If you could provide something I can run locally to reproduce that would really help us. Thanks again for reporting!

[cinnqi]

yes, I tried both at and loc, and none of them worked. i is a row label indeed and mainsnaks is a list of objects, format below

  [
      {
        "snaktype":"value",
        "property":"P1064",
        "datavalue":{
          "value":{
            "entity-type":"item",
            "numeric-id":3319112,
            "id":"Q3319112"
          },
          "type":"wikibase-entityid"
        },
        "datatype":"wikibase-item"
      },
      {
        "snaktype":"value",
        "property":"P31",
        "datavalue":{
          "value":{
            "entity-type":"item",
            "numeric-id":728937,
            "id":"Q728937"
          },
          "type":"wikibase-entityid"
        },
        "datatype":"wikibase-item"
      },
      ........
    ]

I am trying to insert the mainsnaks to one indicated datafram cell. Actually, I don't understand why it can work in pandas.

[mvashishtha]

@cinnqi thanks for describing the data. Could you please also add the line of your code that causes the error?

@devin-petersohn I think this might be another case of someone trying to use loc to append to a dataframe, as in #3764.

[devin-petersohn]

@mvashishtha Yes, it does appear related

[mvashishtha]

@cinnqi because you haven't posted any more information, I'm closing this issue. Hopefully we can solve your bug by fixing #3764. Please comment here if you need more help.