123 lines
2.4 KiB
Python
123 lines
2.4 KiB
Python
"""
|
|
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
|
|
False
|
|
|
|
Subclass of ``UserDict``::
|
|
|
|
>>> ud = UserDictSub(A = 'letter A')
|
|
>>> ud['a'] # ✅
|
|
'letter A'
|
|
>>> ud.get('a', '') # ✅
|
|
'letter A'
|
|
>>> 'a' in ud
|
|
False
|
|
|
|
|
|
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
|
|
False
|
|
|
|
|
|
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 # ✅
|
|
True
|
|
|
|
Subclass of ``abc.Mapping`` with support for ``__missing__``::
|
|
|
|
>>> dms = DictLikeMappingSub(A = 'letter A')
|
|
>>> dms['a'] # ✅
|
|
'letter A'
|
|
>>> dms.get('a', '')
|
|
''
|
|
>>> 'a' in dms
|
|
False
|
|
|
|
|
|
"""
|
|
|
|
from collections import UserDict
|
|
from collections import abc
|
|
|
|
|
|
def _upper(x):
|
|
try:
|
|
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
|