Merge pull request #510 from onyxfish/469

Don't error when reading from /dev/null, fixes #469

csvkit/table.py

@@ -209,28 +209,26 @@ def from_csv(cls, f, name='from_csv_table', snifflimit=None, column_ids=None, bl
         f = six.StringIO(contents)
         rows = agate.reader(f, **kwargs)
 
-        if no_header_row:
-            # Peek at a row to infer column names from
-            row = next(rows)
+        try:
+            if no_header_row:
+                # Peek at a row to infer column names from, and put it back on top
+                row = next(rows)
+                rows = itertools.chain([row], rows)
+                headers = make_default_headers(len(row))
+            else:
+                headers = next(rows)
+        except StopIteration:
+            # The file is `/dev/null`.
+            headers = []
+            pass
 
-            headers = make_default_headers(len(row))
+        if no_header_row or column_ids:
             column_ids = parse_column_identifiers(column_ids, headers, zero_based)
             headers = [headers[c] for c in column_ids]
-            data_columns = [[] for c in headers]
-
-            # Put row back on top
-            rows = itertools.chain([row], rows)
         else:
-            headers = next(rows)
-
-            if column_ids:
-                column_ids = parse_column_identifiers(column_ids, headers, zero_based)
-                headers = [headers[c] for c in column_ids]
-            else:
-                column_ids = range(len(headers))
-
-            data_columns = [[] for c in headers]
+            column_ids = range(len(headers))
 
+        data_columns = [[] for c in headers]
         width = len(data_columns)
 
         for i, row in enumerate(rows):

tests/test_table.py

@@ -91,6 +91,10 @@ def test_from_csv_no_inference(self):
     def test_from_csv_empty_file(self):
         table.Table.from_csv(six.StringIO('\n\n'))
 
+    def test_from_csv_dev_null(self):
+        with open('/dev/null', 'r') as f:
+            table.Table.from_csv(f)
+
     def test_to_csv(self):
         raise SkipTest
         with open('examples/testfixed_converted.csv', 'r') as f: