Pickup specific elements only appear on numeric columns

[otiai10]

Problem

pandas's KeyError is raised when applying infer_schema to some tables which DO NOT include numeric columns.

Traceback (most recent call last):
  File "main.py", line 20, in <module>
    infer_schema.infer_schema(dataframe, 'foobar', sample_size=40)
  File "/usr/local/lib/python3.6/dist-packages/pydqc/infer_schema.py", line 208, in infer_schema
    'sample_uni_percentage', 'sample_min', 'sample_median', 'sample_max', 'sample_std']]
  File "/usr/local/lib/python3.6/dist-packages/pandas/core/frame.py", line 2981, in __getitem__
    indexer = self.loc._convert_to_indexer(key, axis=1, raise_missing=True)
  File "/usr/local/lib/python3.6/dist-packages/pandas/core/indexing.py", line 1271, in _convert_to_indexer
    return self._get_listlike_indexer(obj, axis, **kwargs)[1]
  File "/usr/local/lib/python3.6/dist-packages/pandas/core/indexing.py", line 1078, in _get_listlike_indexer
    keyarr, indexer, o._get_axis_number(axis), raise_missing=raise_missing
  File "/usr/local/lib/python3.6/dist-packages/pandas/core/indexing.py", line 1171, in _validate_read_indexer
    raise KeyError("{} not in index".format(not_found))
KeyError: "['sample_std', 'sample_min', 'sample_max', 'sample_median'] not in index"
root@aa29efcd9fe8:/workspace# vi /usr/local/lib/python3.6/dist-packages/pydqc/infer_schema.py

Reason

Those indices are added _cal_column_stat but only if the type of column is 'numeric'. After that, in infer_schema, it is assumed that at least one of the provided columns is 'numeric' and those indices should exist.

Solution

If there is NO column numeric, don't pick up those columns.