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PERF: don't create the skiprows set if using the c-parser #13005

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PERF: don't create the skiprows set if using the c-parser #13005

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2 changes: 1 addition & 1 deletion doc/source/whatsnew/v0.18.1.txt
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Expand Up @@ -408,7 +408,7 @@ Performance Improvements

- Improved speed of SAS reader (:issue:`12656`)
- Performance improvements in ``.groupby(..).cumcount()`` (:issue:`11039`)

- Improved memory usage in ``pd.read_csv()`` when using ``skiprows=an_integer`` (:issue:`13005`)

- Improved performance of ``DataFrame.to_sql`` when checking case sensitivity for tables. Now only checks if table has been created correctly when table name is not lower case. (:issue:`12876`)
- Improved performance of ``Period`` construction and plotting of ``Period``s. (:issue:`12903`, :issue:`11831`)
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9 changes: 6 additions & 3 deletions pandas/io/parsers.py
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Expand Up @@ -775,9 +775,12 @@ def _clean_options(self, options, engine):
# Converting values to NA
na_values, na_fvalues = _clean_na_values(na_values, keep_default_na)

if com.is_integer(skiprows):
skiprows = lrange(skiprows)
skiprows = set() if skiprows is None else set(skiprows)
# handle skiprows; this is internally handled by the
# c-engine, so only need for python parsers
if engine != 'c':
if com.is_integer(skiprows):
skiprows = lrange(skiprows)
skiprows = set() if skiprows is None else set(skiprows)

# put stuff back
result['names'] = names
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