BUG: Nrows cannot be zero for read_csv. Fixes pandas-dev#21141

pandas/io/parsers.py

@@ -1027,7 +1027,7 @@ def _failover_to_python(self):
         raise com.AbstractMethodError(self)
 
     def read(self, nrows=None):
-        nrows = _validate_integer('nrows', nrows)
+        nrows = _validate_integer('nrows', nrows, min_val=1)
 
         if nrows is not None:
             if self.options.get('skipfooter'):

pandas/tests/io/parser/common.py

@@ -364,7 +364,7 @@ def test_read_nrows(self):
         df = self.read_csv(StringIO(self.data1), nrows=3.0)
         tm.assert_frame_equal(df, expected)
 
-        msg = r"'nrows' must be an integer >=0"
+        msg = r"'nrows' must be an integer >=1"
 
         with tm.assert_raises_regex(ValueError, msg):
             self.read_csv(StringIO(self.data1), nrows=1.2)
@@ -375,6 +375,9 @@ def test_read_nrows(self):
         with tm.assert_raises_regex(ValueError, msg):
             self.read_csv(StringIO(self.data1), nrows=-1)
 
+        with tm.assert_raises_regex(ValueError, msg):
+            self.read_csv(StringIO(self.data1), nrows=0)
+
     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)

pandas/tests/io/test_excel.py

@@ -995,11 +995,18 @@ def test_read_excel_nrows_greater_than_nrows_in_file(self, ext):
 
     def test_read_excel_nrows_non_integer_parameter(self, ext):
         # GH 16645
-        msg = "'nrows' must be an integer >=0"
+        msg = "'nrows' must be an integer >=1"
         with tm.assert_raises_regex(ValueError, msg):
             pd.read_excel(os.path.join(self.dirpath, 'test1' + ext),
                           nrows='5')
 
+    def test_read_excel_nrows_zero_parameter(self, ext):
+        # GH 16645
+        msg = "'nrows' must be an integer >=1"
+        with tm.assert_raises_regex(ValueError, msg):
+            pd.read_excel(os.path.join(self.dirpath, 'test1' + ext),
+                          nrows=0)
+
     def test_read_excel_squeeze(self, ext):
         # GH 12157
         f = os.path.join(self.dirpath, 'test_squeeze' + ext)