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

closes #13005

Author: jreback

doc/source/whatsnew/v0.18.1.txt

@@ -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`)

pandas/io/parsers.py

@@ -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