Fix reading SAS7BDAT files with zero rows

doc/source/whatsnew/v1.5.0.rst

@@ -814,6 +814,7 @@ I/O
 - Bug in :func:`read_excel` when reading a ``.ods`` file with newlines between xml elements (:issue:`45598`)
 - Bug in :func:`read_parquet` when ``engine="fastparquet"`` where the file was not closed on error (:issue:`46555`)
 - :meth:`to_html` now excludes the ``border`` attribute from ``<table>`` elements when ``border`` keyword is set to ``False``.
+- Bug in :func:`read_sas` returned ``None`` rather than an empty DataFrame for SAS7BDAT files with zero rows (:issue:`18198`)
 -
 
 Period

pandas/io/sas/sas7bdat.py

@@ -737,7 +737,7 @@ def read(self, nrows: int | None = None) -> DataFrame | None:
             self.close()
             raise EmptyDataError("No columns to parse from file")
 
-        if self._current_row_in_file_index >= self.row_count:
+        if nrows > 0 and self._current_row_in_file_index >= self.row_count:
             return None
 
         m = self.row_count - self._current_row_in_file_index

pandas/tests/io/sas/test_sas7bdat.py

@@ -216,6 +216,15 @@ def test_zero_variables(datapath):
         pd.read_sas(fname)
 
 
+def test_zero_rows(datapath):
+    # GH 18198
+    fname = datapath("io", "sas", "data", "zero_rows.sas7bdat")
+    df = pd.read_sas(fname)
+    tm.assert_frame_equal(
+        df, pd.DataFrame([{"char_field": "a", "num_field": 1.0}]).iloc[:0]
+    )
+
+
 def test_corrupt_read(datapath):
     # We don't really care about the exact failure, the important thing is
     # that the resource should be cleaned up afterwards (BUG #35566)