refactor: duck-typing reading magic string and try to restore the reader position if possible

Author: ferstar

filetype/utils.py

@@ -73,14 +73,13 @@ def get_bytes(obj):
     if isinstance(obj, pathlib.PurePath):
         return get_signature_bytes(obj)
 
-    if isinstance(obj, BufferedIOBase):
-        start_pos = obj.tell()
-        obj.seek(0)
-        magic_bytes = obj.read(_NUM_SIGNATURE_BYTES)
-        obj.seek(start_pos)  # restore reader position
-        return get_bytes(magic_bytes)
-
     if hasattr(obj, 'read'):
+        if hasattr(obj, 'tell') and hasattr(obj, 'seek'):
+            start_pos = obj.tell()
+            obj.seek(0)
+            magic_bytes = obj.read(_NUM_SIGNATURE_BYTES)
+            obj.seek(start_pos)
+            return get_bytes(magic_bytes)
         return get_bytes(obj.read(_NUM_SIGNATURE_BYTES))
 
     raise TypeError('Unsupported type as file input: %s' % type(obj))