Raised by :None:None:`pd.read_csv` and :None:None:`pd.read_table` when it is necessary to change parsers, generally from the default 'c' parser to 'python'.
It happens due to a lack of support or functionality for parsing a particular attribute of a CSV file with the requested engine.
Currently, 'c' unsupported options include the following parameters:
sep
other than a single character (e.g. regex separators)
:None:None:`skipfooter` higher than 0
:None:None:`sep=None` with :None:None:`delim_whitespace=False`
The warning can be avoided by adding :None:None:`engine='python'` as a parameter in :None:None:`pd.read_csv` and :None:None:`pd.read_table` methods.
Warning raised when reading a file that doesn't use the default 'c' parser.
pd.read_csv
Read CSV (comma-separated) file into DataFrame.
pd.read_table
Read general delimited file into DataFrame.
Using a sep
in :None:None:`pd.read_csv` other than a single character:
>>> import io
... csv = '''a;b;c
... 1;1,8
... 1;2,1'''
... df = pd.read_csv(io.StringIO(csv), sep='[;,]') # doctest: +SKIP
... # ParserWarning: Falling back to the 'python' engine...
Adding :None:None:`engine='python'` to :None:None:`pd.read_csv` removes the Warning:
>>> df = pd.read_csv(io.StringIO(csv), sep='[;,]', engine='python')See :
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