Add AttributeDict class

A class that stores values in a dictionary, but whose keys are also
exposed as attributes.

thermocepstrum/utils/attributedict.py

@@ -0,0 +1,79 @@
+# -*- coding: utf-8 -*-
+
+
+class AttributeDict(dict):   # pylint: disable=too-many-instance-attributes
+    """
+    This class internally stores values in a dictionary, but exposes
+    the keys also as attributes, i.e. asking for attrdict.key
+    will return the value of attrdict['key'] and so on.
+
+    Raises an AttributeError if the key does not exist, when called as an attribute,
+    while the usual KeyError if the key does not exist and the dictionary syntax is
+    used.
+    """
+
+    def __init__(self, dictionary=None):
+        """Recursively turn the `dict` and all its nested dictionaries into `AttributeDict` instance."""
+        super().__init__()
+        if dictionary is None:
+            dictionary = {}
+
+        for key, value in dictionary.items():
+            if isinstance(value, Mapping):
+                self[key] = AttributeDict(value)
+            else:
+                self[key] = value
+
+    def __repr__(self):
+        """Representation of the object."""
+        return f'{self.__class__.__name__}({dict.__repr__(self)})'
+
+    def __getattr__(self, attr):
+        """Read a key as an attribute.
+
+        :raises AttributeError: if the attribute does not correspond to an existing key.
+        """
+        try:
+            return self[attr]
+        except KeyError:
+            errmsg = f"'{self.__class__.__name__}' object has no attribute '{attr}'"
+            raise AttributeError(errmsg)
+
+    def __setattr__(self, attr, value):
+        """Set a key as an attribute."""
+        try:
+            self[attr] = value
+        except KeyError:
+            raise AttributeError(
+                f"AttributeError: '{attr}' is not a valid attribute of the object '{self.__class__.__name__}'")
+
+    def __delattr__(self, attr):
+        """Delete a key as an attribute.
+
+        :raises AttributeError: if the attribute does not correspond to an existing key.
+        """
+        try:
+            del self[attr]
+        except KeyError:
+            errmsg = f"'{self.__class__.__name__}' object has no attribute '{attr}'"
+            raise AttributeError(errmsg)
+
+    def __deepcopy__(self, memo=None):
+        """Deep copy."""
+        from copy import deepcopy
+
+        if memo is None:
+            memo = {}
+        retval = deepcopy(dict(self))
+        return self.__class__(retval)
+
+    def __getstate__(self):
+        """Needed for pickling this class."""
+        return self.__dict__.copy()
+
+    def __setstate__(self, dictionary):
+        """Needed for pickling this class."""
+        self.__dict__.update(dictionary)
+
+    def __dir__(self):
+        return self.keys()