Fix _parse_prefilter_string to remain non-filtered channels

mne/io/edf/edf.py

@@ -758,26 +758,18 @@ def _get_info(
     return info, edf_info, orig_units
 
 
+def _extract_filter_value(s, prefix, suffix):
+    if prefix in s:
+        start = s.find(prefix) + len(prefix)
+        end = s.find(suffix, start)
+        return s[start:end].strip()
+    return None
+
+
 def _parse_prefilter_string(prefiltering):
     """Parse prefilter string from EDF+ and BDF headers."""
-    highpass = np.array(
-        [
-            v
-            for hp in [
-                re.findall(r"HP:\s*([0-9]+[.]*[0-9]*)", filt) for filt in prefiltering
-            ]
-            for v in hp
-        ]
-    )
-    lowpass = np.array(
-        [
-            v
-            for hp in [
-                re.findall(r"LP:\s*([0-9]+[.]*[0-9]*)", filt) for filt in prefiltering
-            ]
-            for v in hp
-        ]
-    )
+    highpass = [_extract_filter_value(s, "HP:", "Hz") for s in prefiltering]
+    lowpass = [_extract_filter_value(s, "LP:", "Hz") for s in prefiltering]
     return highpass, lowpass
 
 

mne/io/edf/tests/test_edf.py

@@ -652,6 +652,11 @@ def test_edf_prefilter_parse():
     assert_array_equal(highpass, ["0.1"])
     assert_array_equal(lowpass, ["75"])
 
+    prefilter_edf_specs_doc = ["", "HP:0.1Hz LP:75Hz N:50Hz", ""]
+    highpass, lowpass = _parse_prefilter_string(prefilter_edf_specs_doc)
+    assert_array_equal(highpass, [None, "0.1", None])
+    assert_array_equal(lowpass, [None, "75", None])
+
 
 @testing.requires_testing_data
 @pytest.mark.parametrize("fname", [test_generator_edf, test_generator_bdf])