BUG: np.loadtxt cannot load text file with quoted fields separated by whitespace (#22906)

Fix issue with `delimiter=None` and quote character not working properly (not using whitespace delimiter mode).

Closes gh-22899

2 files changed, 22 insertions, 0 deletions

diff --git a/numpy/lib/npyio.py b/numpy/lib/npyio.py
index 4a27c7898..71d600c30 100644
--- a/numpy/lib/npyio.py
+++ b/numpy/lib/npyio.py
@@ -1303,6 +1303,14 @@ def loadtxt(fname, dtype=float, comments='#', delimiter=None,
     array([('alpha, #42', 10.), ('beta, #64',  2.)],
           dtype=[('label', '<U12'), ('value', '<f8')])
 
+    Quoted fields can be separated by multiple whitespace characters:
+
+    >>> s = StringIO('"alpha, #42"       10.0\n"beta, #64" 2.0\n')
+    >>> dtype = np.dtype([("label", "U12"), ("value", float)])
+    >>> np.loadtxt(s, dtype=dtype, delimiter=None, quotechar='"')
+    array([('alpha, #42', 10.), ('beta, #64',  2.)],
+          dtype=[('label', '<U12'), ('value', '<f8')])
+
     Two consecutive quote characters within a quoted field are treated as a
     single escaped character:
 
diff --git a/numpy/lib/tests/test_loadtxt.py b/numpy/lib/tests/test_loadtxt.py
index 819a8dda4..8a5b044b8 100644
--- a/numpy/lib/tests/test_loadtxt.py
+++ b/numpy/lib/tests/test_loadtxt.py
@@ -534,6 +534,20 @@ def test_quoted_field(q):
     assert_array_equal(res, expected)
 
 
+@pytest.mark.parametrize("q", ('"', "'", "`"))
+def test_quoted_field_with_whitepace_delimiter(q):
+    txt = StringIO(
+        f"{q}alpha, x{q}     2.5\n{q}beta, y{q} 4.5\n{q}gamma, z{q}   5.0\n"
+    )
+    dtype = np.dtype([('f0', 'U8'), ('f1', np.float64)])
+    expected = np.array(
+        [("alpha, x", 2.5), ("beta, y", 4.5), ("gamma, z", 5.0)], dtype=dtype
+    )
+
+    res = np.loadtxt(txt, dtype=dtype, delimiter=None, quotechar=q)
+    assert_array_equal(res, expected)
+
+
 def test_quote_support_default():
     """Support for quoted fields is disabled by default."""
     txt = StringIO('"lat,long", 45, 30\n')