Added test for #7626

Author: jeffcarey

pandas/io/tests/parser/common.py

@@ -427,6 +427,18 @@ def test_read_nrows(self):
         with tm.assertRaisesRegexp(ValueError, msg):
             self.read_csv(StringIO(self.data1), nrows='foo')
 
+    def test_read_nrows_large(self):
+        # GH-7626 - Read only nrows of data read in for large inputs (>262144b)
+        header_narrow = '\t'.join(['COL_HEADER_'+str(i) for i in range(10)]) + '\n'
+        data_narrow = '\t'.join(['somedatasomedatasomedata1' for i in range(10)])+'\n'
+        header_wide = '\t'.join(['COL_HEADER_'+str(i) for i in range(15)]) + '\n'
+        data_wide = '\t'.join(['somedatasomedatasomedata2' for i in range(15)])+'\n'
+        test_input = header_narrow + data_narrow*1050 + header_wide + data_wide*2
+
+        df = self.read_table(StringIO(test_input), nrows=1010)
+
+        self.assertTrue(df.size == 1010*10)
+
     def test_read_chunksize(self):
         reader = self.read_csv(StringIO(self.data1), index_col=0, chunksize=2)
         df = self.read_csv(StringIO(self.data1), index_col=0)