updates to ch.14

14-inheritance/uppermixin.py

@@ -0,0 +1,115 @@
+"""UpperDict uppercases all string keys.
+
+Test for initializer. `str` keys are uppercased::
+
+    >>> d = UpperDict([('a', 'letter A'), ('B', 'letter B'), (2, 'digit two')])
+    >>> list(d.keys())
+    ['A', 'B', 2]
+
+Tests for item retrieval using `d[key]` notation::
+
+    >>> d['A']
+    'letter A'
+    >>> d['b']
+    'letter B'
+    >>> d[2]
+    'digit two'
+
+
+Tests for missing key::
+
+    >>> d['z']
+    Traceback (most recent call last):
+      ...
+    KeyError: 'Z'
+    >>> d[99]
+    Traceback (most recent call last):
+      ...
+    KeyError: 99
+
+
+Tests for item retrieval using `d.get(key)` notation::
+
+    >>> d.get('a')
+    'letter A'
+    >>> d.get('B')
+    'letter B'
+    >>> d.get(2)
+    'digit two'
+    >>> d.get('z', '(not found)')
+    '(not found)'
+
+Tests for the `in` operator::
+
+    >>> ('a' in d, 'B' in d, 'z' in d)
+    (True, True, False)
+
+Test for item assignment using lowercase key::
+
+    >>> d['c'] = 'letter C'
+    >>> d['C']
+    'letter C'
+
+Tests for update using a `dict` or a sequence of pairs::
+
+    >>> d.update({'D': 'letter D', 'e': 'letter E'})
+    >>> list(d.keys())
+    ['A', 'B', 2, 'C', 'D', 'E']
+    >>> d.update([('f', 'letter F'), ('G', 'letter G')])
+    >>> list(d.keys())
+    ['A', 'B', 2, 'C', 'D', 'E', 'F', 'G']
+    >>> d  # doctest:+NORMALIZE_WHITESPACE
+    {'A': 'letter A', 'B': 'letter B', 2: 'digit two',
+    'C': 'letter C', 'D': 'letter D', 'E': 'letter E',
+    'F': 'letter F', 'G': 'letter G'}
+
+UpperCounter uppercases all `str` keys.
+
+Test for initializer: keys are uppercased.
+
+    >>> d = UpperCounter('AbracAdaBrA')
+    >>> sorted(d.keys())
+    ['A', 'B', 'C', 'D', 'R']
+
+Tests for count retrieval using `d[key]` notation::
+
+    >>> d['a']
+    5
+    >>> d['z']
+    0
+
+"""
+# tag::UPPERCASE_MIXIN[]
+import collections
+
+
+def _upper(key):  # <1>
+    try:
+        return key.upper()
+    except AttributeError:
+        return key
+
+
+class UpperCaseMixin:  # <2>
+    def __setitem__(self, key, item):
+        super().__setitem__(_upper(key), item)
+
+    def __getitem__(self, key):
+        return super().__getitem__(_upper(key))
+
+    def get(self, key, default=None):
+        return super().get(_upper(key), default)
+
+    def __contains__(self, key):
+        return super().__contains__(_upper(key))
+# end::UPPERCASE_MIXIN[]
+
+# tag::UPPERDICT[]
+class UpperDict(UpperCaseMixin, collections.UserDict):  # <1>
+    pass
+
+
+class UpperCounter(UpperCaseMixin, collections.Counter):  # <2>
+    """Specialized 'Counter' that uppercases string keys"""  # <3>
+
+# end::UPPERDICT[]