dol.appendable

dol.appendable(store_cls=None, *, item2kv, return_keys=False, __module__=None, __name__=None, __qualname__=None, __doc__=None, __annotations__=None, __defaults__=None, __kwdefaults__=None)

Makes a new class with append (and consequential extend) methods

Parameters:

• store_cls – The store class to subclass

• item2kv – The function that produces a (key, val) pair from an item

• new_store_name – The name to give the new class (default will be ‘Appendable’ + store_cls.__name__)

Returns:

append, and extend.

Return type:

A subclass of store_cls with two additional methods

>>> item_to_kv = lambda item: (item['L'], item)  # use value of 'L' as the key, and value is the item itself
>>> MyStore = appendable(dict, item2kv=item_to_kv)
>>> s = MyStore(); s.append({'L': 'let', 'I': 'it', 'G': 'go'}); list(s.items())
[('let', {'L': 'let', 'I': 'it', 'G': 'go'})]

Use mk_item2kv.from_item_to_key_params_and_val with tuple key params

>>> item_to_kv = appendable.mk_item2kv_for.item_to_key_params_and_val(lambda x: ((x['L'], x['I']), x['G']), '{}/{}')
>>> MyStore = appendable(item2kv=item_to_kv)(dict)  # showing the append(...)(store) form
>>> s = MyStore(); s.append({'L': 'let', 'I': 'it', 'G': 'go'}); list(s.items())
[('let/it', 'go')]

Use mk_item2kv.from_item_to_key_params_and_val with dict key params

>>> item_to_kv = appendable.mk_item2kv_for.item_to_key_params_and_val(
...     lambda x: ({'L': x['L'], 'G': x['G']}, x['I']), '{G}_{L}')
>>> @appendable(item2kv=item_to_kv)  # showing the @ form
... class MyStore(dict):
...     pass
>>> s = MyStore(); s.append({'L': 'let', 'I': 'it', 'G': 'go'}); list(s.items())
[('go_let', 'it')]

Use mk_item2kv.fields to get a tuple key from item fields, defining the sub-dict of the remaining fields to be the value. Also showing here how you can decorate the instance itself.

>>> item_to_kv = appendable.mk_item2kv_for.fields(['G', 'L'], key_as_tuple=True)
>>> d = {}
>>> s = appendable(d, item2kv=item_to_kv)
>>> s.append({'L': 'let', 'I': 'it', 'G': 'go'}); list(s.items())
[(('go', 'let'), {'I': 'it'})]

You can make the “append” and “extend” methods to return the new generated keys by using the “return_keys” flag.

>>> d = {}
>>> s = appendable(d, item2kv=item_to_kv, return_keys=True)
>>> s.append({'L': 'let', 'I': 'it', 'G': 'go'})
('go', 'let')