Fix for SPMFile instantiation

spmpy/spmloader.py

@@ -17,16 +17,14 @@
 class SPMFile:
     """ Representation of an entire SPM file with images and metadata """
 
-    def __new__(cls, *args, **kwargs):
-        """ If class is instanced with a single parameter, it is either a path or bytestring """
-        if len(args) == 1 and isinstance(args[0], (str, Path)):
-            return cls.from_path(args[0])
+    def __init__(self, spmfile: str | PathLike | bytes):
+        if isinstance(spmfile, (str, Path)):
+            self.path = Path(spmfile)
+            bytestring = self.load_from_file(spmfile)
+        elif isinstance(spmfile, bytes):
+            bytestring = spmfile
         else:
-            return super().__new__(cls)
-
-    def __init__(self, bytestring: bytes, path: str | PathLike = None):
-        if path:
-            self.path: Path = Path(path)
+            raise ValueError('SPM file must be path to spm file or raw bytestring')
 
         self.header: dict = self.parse_header(bytestring)
         self.images: dict = self.extract_ciao_images(self.header, bytestring)
@@ -60,13 +58,13 @@ def groups(self) -> dict[int | None, dict[str]]:
 
         return groups
 
-    @classmethod
-    def from_path(cls, path):
+    @staticmethod
+    def load_from_file(path):
         """ Load SPM data from a file on disk """
         with open(path, 'rb') as f:
             bytestring = f.read()
 
-        return cls(bytestring, path=path)
+        return bytestring
 
     @staticmethod
     def parse_header(bytestring) -> dict:
@@ -251,12 +249,12 @@ def interpret_file_header(header_bytetring: bytes, encoding: str = 'latin-1') \
     n_image = 0
 
     # Walk through each line of metadata and extract sections and parameters
-    for line in header_lines:
-        if line.startswith(b'\\*File list end'):
+    for line_bytes in header_lines:
+        if line_bytes == b'\\*File list end':
             # End of header, break out of loop
             break
 
-        line = line.decode(encoding).lstrip('\\')
+        line = line_bytes.decode(encoding).lstrip('\\')
         if line.startswith('*'):
             # Lines starting with * indicate a new section
             current_section = line.strip('*')