BUG: Fix types of errors raised by genfromtxt (#20389)

2 files changed, 14 insertions, 11 deletions

diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py
index 85e26f094..a839b892a 100644
--- a/numpy/lib/npyio.py
+++ b/numpy/lib/npyio.py
@@ -1807,22 +1807,21 @@ def genfromtxt(fname, dtype=float, comments='#', delimiter=None,
         byte_converters = False
 
     # Initialize the filehandle, the LineSplitter and the NameValidator
+    if isinstance(fname, os_PathLike):
+        fname = os_fspath(fname)
+    if isinstance(fname, str):
+        fid = np.lib._datasource.open(fname, 'rt', encoding=encoding)
+        fid_ctx = contextlib.closing(fid)
+    else:
+        fid = fname
+        fid_ctx = contextlib.nullcontext(fid)
     try:
-        if isinstance(fname, os_PathLike):
-            fname = os_fspath(fname)
-        if isinstance(fname, str):
-            fid = np.lib._datasource.open(fname, 'rt', encoding=encoding)
-            fid_ctx = contextlib.closing(fid)
-        else:
-            fid = fname
-            fid_ctx = contextlib.nullcontext(fid)
         fhd = iter(fid)
     except TypeError as e:
         raise TypeError(
-            f"fname must be a string, filehandle, list of strings,\n"
-            f"or generator. Got {type(fname)} instead."
+            "fname must be a string, a filehandle, a sequence of strings,\n"
+            f"or an iterator of strings. Got {type(fname)} instead."
         ) from e
-
     with fid_ctx:
         split_line = LineSplitter(delimiter=delimiter, comments=comments,
                                   autostrip=autostrip, encoding=encoding)
diff --git a/numpy/lib/tests/test_io.py b/numpy/lib/tests/test_io.py
index 5201b8e6e..c19660cf0 100644
--- a/numpy/lib/tests/test_io.py
+++ b/numpy/lib/tests/test_io.py
@@ -1425,6 +1425,10 @@ class TestFromTxt(LoadTxtBase):
                             ('F', 25.0, 60.0)], dtype=descriptor)
         assert_equal(test, control)
 
+    def test_bad_fname(self):
+        with pytest.raises(TypeError, match='fname must be a string,'):
+            np.genfromtxt(123)
+
     def test_commented_header(self):
         # Check that names can be retrieved even if the line is commented out.
         data = TextIO("""