iframe-proxy | Sunbelt Computer Software

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Semantics of ``__missing__`` across mappings.
✅ = indicates ``__missing__`` was called
Subclass of ``dict``::
    >>> d = DictSub(A = 'letter A')
    >>> d['a']  # ✅
    'letter A'
    >>> d.get('a', '')
    >>> 'a' in d
Subclass of ``UserDict``::
    >>> ud = UserDictSub(A = 'letter A')
    >>> ud['a']  # ✅
    'letter A'
    >>> ud.get('a', '')  # ✅
    'letter A'
    >>> 'a' in ud
Simple subclass of ``abc.Mapping``::
    >>> sms = SimpleMappingSub(A = 'letter A')
    >>> sms['a']
    Traceback (most recent call last):
    KeyError: 'a'
    >>> sms.get('a', '')
    >>> 'a' in sms
Subclass of ``abc.Mapping`` with support for ``__missing__``::
    >>> mms = MappingMissingSub(A = 'letter A')
    >>> mms['a']  # ✅
    'letter A'
    >>> mms.get('a', '')  # ✅
    'letter A'
    >>> 'a' in mms  # ✅
Subclass of ``abc.Mapping`` with support for ``__missing__``::
    >>> dms = DictLikeMappingSub(A = 'letter A')
    >>> dms['a']  # ✅
    'letter A'
    >>> dms.get('a', '')
    >>> 'a' in dms
from collections import UserDict
from collections import abc
def _upper(x):
        return x.upper()
    except AttributeError:
        return x
class DictSub(dict):
    def __missing__(self, key):
        return self[_upper(key)]
class UserDictSub(UserDict):
    def __missing__(self, key):
        return self[_upper(key)]
class SimpleMappingSub(abc.Mapping):
    def __init__(self, *args, **kwargs):
        self._data = dict(*args, **kwargs)
    # next three methods: abstract in ABC
    def __getitem__(self, key):
        return self._data[key]
    def __len__(self):
        return len(self._data)
    def __iter__(self):
        return iter(self._data)
    # never called by instances of this class
    def __missing__(self, key):
        return self[_upper(key)]
class MappingMissingSub(SimpleMappingSub):
    def __getitem__(self, key):
        try:
            return self._data[key]
        except KeyError:
            return self[_upper(key)]
class DictLikeMappingSub(SimpleMappingSub):
    def __getitem__(self, key):
        try:
            return self._data[key]
        except KeyError:
            return self[_upper(key)]
    def get(self, key, default=None):
        return self._data.get(key, default)
    def __contains__(self, key):
        return key in self._data

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