python-dict-wrapper 0.4

Wraps python dictionary keys are attributes

Python Dict Wrapper

This is a simple class the exposes a dictionary’s keys as class attributes, making for less typing when accessing dictionary values. This class also enforces that the dictionary’s overall shape is enforced.

A common use of this class may be in retrieving and updating model object retrieves from web services (i.e. RESTful web services) where the shape of the model object must be maintained.

Example:

from python_dict_wrapper import DictWrapper

actor = {
    "name": "Steve Carell",
    "career": [{
        "medium": "TV",
        "title": "The Office"
    }, {
        "medium": "MOVIE",
        "title": "Bruce Almighty"
    }]
}

wrapper = DictWrapper(actor)
wrapper.career[1].title = "Despicable Me"

print(wrapper.to_json(pretty=True))

class DictWrapper(dict, strict=False)

Each DictWrapper instance takes two arguments: * dict - A python dictionary that the wrapper will use as it’s source. * strict - An optional boolean that indicates if the wrapper should enforce types when setting attribute values. * key_prefix - A string or list of strings that contains characters that dictionary keys should be prefixed with before they become attributes.

Attributes

Once a DictWrapper instance has been created, the keys of it’s source dictionary will be exposed as attributes. So for example if a DictWrapper is instanciated with the following dictionary:

>>> from dict_wrapper import DictWrapper
>>> address_dict = {'street': '221B Baker Street', 'city': 'London', 'country': 'UK'}
>>> address = DictWrapper(address_dict)

The keys: street, city, and ‘country’ will be exposed as attributes of address

>>> address.street
'221B Baker Street'
>>> address.city
'London'
>>> address.country
'UK'

The attributes are both readable and writeable, so you can update the values simply by assigning to them:

>>> address.country = "United Kingdom"
>>> address.country
'United Kingdom'

If the strict argument to the constructor was set to True, then the DictWrapper will enforce that that when you assign a new value to an attribute, it must be the same Type as the original dictionary value.

>>> address = DictWrapper(address_dict, strict=True)
>>> address.street = 221
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "dict_wrapper.py", line 62, in __setattr__
    raise TypeError("Value for %s must be a %s, not %s" % (
TypeError: Value for street must be a str, not int

If the key_prefix argument to the constructor is set to a string or list of strings, attributes in the dictionary are searched without their prefixes. This is typically used for dictionaries that have keys that cannot be represented in attributes. Here’s an example:

>>> the_dict = {'@timestamp': '2020-04-19 05:00:00', 'author': 'Arthur Conan Doyle'}
>>>
>>> entry = DictWrapper(the_dict)
>>> entry.timestamp
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "python_dict_wrapper.py", line 49, in __getattr__
    self._check_for_bad_attribute(key)
  File "python_dict_wrapper.py", line 87, in _check_for_bad_attribute
    raise AttributeError("'%s' object has no attribute '%s'" % (self.__class__.__name__, key))
AttributeError: 'DictWrapper' object has no attribute 'timestamp'
>>>
>>>
>>> entry = DictWrapper(the_dict, key_prefix='@')
>>> entry.timestamp
'2020-04-19 05:00:00'

Methods

DictWrapper instances have to methods: to_json() and to_dict().

to_json(pretty=False)

Converts the dictionary values to a JSON string. If the pretty argument is set to True, the returned JSON will be multi-lined and indented with 4 characters. If it’s false, the returned JSON will a single-line of text.

to_dict()

Converts the DictWrapper back to a Python dictionary.

Nesting

DictWrapper instances should be able to handle nested dictionaries and lists without issue. It automatically wraps any nested dictionaries in their own DictWrapper instances for you.

>>> shelock_dict = {
...     'name': 'Sherlock Holmes',
...     'address': {
...             'street': '221B Baker Street',
...             'city': 'London',
...             'country': 'UK'
...     }
... }
>>> sherlock = DictWrapper(sherlock_dict)
>>> sherlock.address.country = 'United Kingdom'
>>> print(sherlock.to_json(pretty=True))
{
    "name": "Sherlock Holmes",
    "address": {
        "street": "221B Baker Street",
        "city": "London",
        "country": "United Kingdom"
    }
}