read_csv: if parse_dates dont appear in use_cols, we get a trace #31251
Description
Code Sample, a copy-pastable example if possible
# Your code here import pandas as pd import io content = io.StringIO(''' time,val 212.23, 32 ''') date_cols = ['time'] df = pd.read_csv( content, sep=',', usecols=['val'], dtype= { 'val': int }, parse_dates=date_cols, )Problem description
triggers
Traceback (most recent call last): File "test.py", line 16, in <module> parse_dates=date_cols, File "/nix/store/k4fd48jzsyafvcifa6wi6pk4vaprnw36-python3.7-pandas-0.25.3/lib/python3.7/site-packages/pandas/io/parsers.py", line 685, in parser_f return _read(filepath_or_buffer, kwds) File "/nix/store/k4fd48jzsyafvcifa6wi6pk4vaprnw36-python3.7-pandas-0.25.3/lib/python3.7/site-packages/pandas/io/parsers.py", line 463, in _read data = parser.read(nrows) File "/nix/store/k4fd48jzsyafvcifa6wi6pk4vaprnw36-python3.7-pandas-0.25.3/lib/python3.7/site-packages/pandas/io/parsers.py", line 1154, in read ret = self._engine.read(nrows) File "/nix/store/k4fd48jzsyafvcifa6wi6pk4vaprnw36-python3.7-pandas-0.25.3/lib/python3.7/site-packages/pandas/io/parsers.py", line 2134, in read names, data = self._do_date_conversions(names, data) File "/nix/store/k4fd48jzsyafvcifa6wi6pk4vaprnw36-python3.7-pandas-0.25.3/lib/python3.7/site-packages/pandas/io/parsers.py", line 1885, in _do_date_conversions keep_date_col=self.keep_date_col, File "/nix/store/k4fd48jzsyafvcifa6wi6pk4vaprnw36-python3.7-pandas-0.25.3/lib/python3.7/site-packages/pandas/io/parsers.py", line 3335, in _process_date_conversion data_dict[colspec] = converter(data_dict[colspec]) KeyError: 'time' i.e., if you use columns in parse_dates that dont appear in use_cols, then you are screwed.
Either parse_dates sould be added to use_cols or the documentation precise it. An assert could make the error more understandable too.
pandas 0.25.3