feat: failing to load a pattern will now raise an error instead of returning -1

Author: CPrescher

glassure/pattern.py

@@ -64,6 +64,7 @@ def load(self, filename: str, skiprows: int = 0):
 
         :param filename: path to the file
         :param skiprows: number of rows to skip when loading the data (header)
+        :raises PatternLoadError: if the file cannot be loaded
         """
         try:
             if filename.endswith(".chi"):
@@ -73,18 +74,25 @@ def load(self, filename: str, skiprows: int = 0):
             self.y = data.T[1]
             self.name = os.path.basename(filename).split(".")[:-1][0]
 
-        except ValueError:
-            print("Wrong data format for pattern file! - " + filename)
-            return -1
+        except FileNotFoundError:
+            raise PatternLoadError(filename, "File not found")
+        except OSError as e:
+            raise PatternLoadError(filename, f"OS error: {e}")
+        except ValueError as e:
+            raise PatternLoadError(filename, f"Wrong data format: {e}")
+        except Exception as e:
+            raise PatternLoadError(filename, f"Unexpected error: {e}")
 
     @staticmethod
-    def from_file(filename: str, skip_rows: int = 0) -> Pattern | int:
+    def from_file(filename: str, skip_rows: int = 0) -> Pattern:
         """
         Loads a pattern from a file. The file can be either a .xy or a .chi file. The .chi file will be loaded with
         skiprows=4 by default.
 
         :param filename: path to the file
         :param skip_rows: number of rows to skip when loading the data (header)
+        :return: Pattern object loaded from the file
+        :raises PatternLoadError: if the file cannot be loaded
         """
         try:
             if filename.endswith(".chi"):
@@ -95,9 +103,14 @@ def from_file(filename: str, skip_rows: int = 0) -> Pattern | int:
             name = os.path.basename(filename).split(".")[:-1][0]
             return Pattern(x, y, name)
 
-        except ValueError:
-            print("Wrong data format for pattern file! - " + filename)
-            return -1
+        except FileNotFoundError:
+            raise PatternLoadError(filename, "File not found")
+        except OSError as e:
+            raise PatternLoadError(filename, f"OS error: {e}")
+        except ValueError as e:
+            raise PatternLoadError(filename, f"Wrong data format: {e}")
+        except Exception as e:
+            raise PatternLoadError(filename, f"Unexpected error: {e}")
 
     def save(self, filename: str, header: str = ""):
         """
@@ -369,6 +382,17 @@ def __str__(self):
         )
 
 
+class PatternLoadError(Exception):
+    """Exception raised when a pattern file cannot be loaded."""
+
+    def __init__(self, filename: str, reason: str):
+        self.filename = filename
+        self.reason = reason
+
+    def __str__(self):
+        return f"Failed to load pattern from file '{self.filename}': {self.reason}"
+
+
 def validate(value):
     """
     Validates a numpy array. If the value is a list, it is converted to a numpy array.

tests/test_calc.py

@@ -17,11 +17,6 @@ def prepare_input():
     data_pattern = Pattern.from_file(data_path)
     bkg_pattern = Pattern.from_file(bkg_path)
 
-    if not isinstance(data_pattern, Pattern):
-        raise ValueError(f"Failed to load data pattern from {data_path}")
-    if not isinstance(bkg_pattern, Pattern):
-        raise ValueError(f"Failed to load background pattern from {bkg_path}")
-
     data_config, calculation_config = create_calculate_pdf_configs(
         data_pattern,
         composition={"Mg": 2, "Si": 1, "O": 4},

tests/test_optimization.py

@@ -48,8 +48,6 @@ def sample(data_path, bkg_path):
     """Create a sample pattern by subtracting background from data."""
     data = Pattern.from_file(data_path)
     bkg = Pattern.from_file(bkg_path)
-    assert isinstance(data, Pattern)
-    assert isinstance(bkg, Pattern)
 
     sample = data - bkg
     return sample.limit(1, 17)
@@ -169,8 +167,6 @@ def test_optimize_sq_fit_SiO2(sq, atomic_density):
 def test_optimize_density_SiO2(data_path, bkg_path):
     data = Pattern.from_file(data_path)
     background = Pattern.from_file(bkg_path)
-    assert isinstance(data, Pattern)
-    assert isinstance(background, Pattern)
     composition = {"Si": 1.0, "O": 2.0}
     density = 2.2
 
@@ -198,8 +194,6 @@ def test_optimize_density_SiO2(data_path, bkg_path):
 def test_optimize_density_Mg2SiO4():
     data = Pattern.from_file(data_path_glass)
     background = Pattern.from_file(background_path_glass)
-    assert isinstance(data, Pattern)
-    assert isinstance(background, Pattern)
 
     composition = {"Mg": 2.0, "Si": 1.0, "O": 4.0}
     density = 3.21
@@ -227,8 +221,6 @@ def test_optimize_density_Mg2SiO4():
 def test_optimize_density_method():
     data = Pattern.from_file(data_path_glass)
     background = Pattern.from_file(background_path_glass)
-    assert isinstance(data, Pattern)
-    assert isinstance(background, Pattern)
     composition = {"Mg": 2.0, "Si": 1.0, "O": 4.0}
     density = 3.21
 
@@ -263,8 +255,6 @@ def test_optimize_density_method():
 def test_optimize_density_method_nelder():
     data = Pattern.from_file(data_path_glass)
     background = Pattern.from_file(background_path_glass)
-    assert isinstance(data, Pattern)
-    assert isinstance(background, Pattern)
 
     composition = {"Mg": 2.0, "Si": 1.0, "O": 4.0}
     density = 3.21
@@ -310,8 +300,6 @@ def test_optimize_density_method_nelder():
 def test_optimize_density_vary_bkg_scaling():
     data = Pattern.from_file(data_path_glass)
     background = Pattern.from_file(background_path_glass)
-    assert isinstance(data, Pattern)
-    assert isinstance(background, Pattern)
 
     composition = {"Mg": 2.0, "Si": 1.0, "O": 4.0}
     density = 3.21
@@ -342,8 +330,6 @@ def test_optimize_density_vary_bkg_scaling():
 def test_invalid_optimize_density_method():
     data = Pattern.from_file(data_path_glass)
     background = Pattern.from_file(background_path_glass)
-    assert isinstance(data, Pattern)
-    assert isinstance(background, Pattern)
 
     composition = {"Mg": 2.0, "Si": 1.0, "O": 4.0}
     density = 3.21

tests/test_pattern.py

@@ -1,8 +1,9 @@
 # -*- coding: utf-8 -*-
 import numpy as np
+import pytest
 from pytest import approx
 from pydantic import BaseModel
-from glassure.pattern import PydanticNpArray
+from glassure.pattern import PydanticNpArray, PatternLoadError
 
 from glassure import Pattern
 
@@ -147,3 +148,22 @@ def test_pydantic_nparray_from_json():
     input = {"x": [1, 2, 3]}
     t = DummyModel(**input)
     assert np.array_equal(t.x, np.array([1, 2, 3]))
+
+
+def test_from_file_raises_exception_for_nonexistent_file():
+    """Test that from_file raises PatternLoadError for nonexistent files."""
+    with pytest.raises(PatternLoadError) as exc_info:
+        Pattern.from_file("nonexistent_file.xy")
+    assert "nonexistent_file.xy" in str(exc_info.value)
+    assert "File not found" in str(exc_info.value)
+
+
+def test_from_file_raises_exception_for_invalid_format(tmp_path):
+    """Test that from_file raises PatternLoadError for invalid file format."""
+    invalid_file = tmp_path / "invalid.xy"
+    invalid_file.write_text("not a valid pattern file\ninvalid data")
+    
+    with pytest.raises(PatternLoadError) as exc_info:
+        Pattern.from_file(str(invalid_file))
+    assert "invalid.xy" in str(exc_info.value)
+    assert "Wrong data format" in str(exc_info.value)