datahold 0.4.2

datahold

Overview

Wrap common mutable datastructures for inheritance with modification.

Content

BaseList

To understand the class BaseList here the beginning of its code:

class BaseList:

    data: list

    @functools.wraps(list.__add__)
    def __add__(self, *args, **kwargs):
        data = self.data
        ans = data.__add__(*args, **kwargs)
        self.data = data
        return ans

The following methods are defined this way: __add__, __contains__, __delitem__, __eq__, __format__, __ge__, __getitem__, __gt__, __hash__, __iadd__, __imul__, __iter__, __le__, __len__, __lt__, __mul__, __repr__, __reversed__, __rmul__, __setitem__, __str__, append, clear, copy, count, extend, index, insert, pop, remove, reverse, sort.

The only function present in list and absent in BaseList is __class_getitem__

We can use BaseList as parent for a list-like class. It is recommended to implement in the subclass:

• a property named data with getter and setter wrapping a private variable (for example named _data)

• the __init__ magic method

This allows the creatation of a list-like class with modified behaviour with only minimal effort. To enhance perpormance we can overwrite some of the methods.

OkayList

This class inherits from BaseList. It implements a data property that binds a variable _data.

@property
def data(self, /):
    return list(self._data)

@data.setter
def data(self, values, /):
    self._data = list(values)

@data.deleter
def data(self, /):
    self._data = list()

Based on that it implements common sense methods. For example:

• all methods that cannot actually change the underlying object are now bound to _data instead of data

• all methods that returned a list before now return OkayList (type adapts to further inheritance)

• __bool__ is implemented as bool(len(self)) because list.__bool__ does not exist

• __hash__ raises now a more fitting exception

• __init__ allows now to set data immediately

• the comparison operations are overwritten:

  • __eq__ returns True iff types are equal and _data is equal

  • __ne__ negates __eq__

  • __ge__ returns type(self)(other) <= self

  • __gt__ returns True iff __eq__ returns False and __ge__ returns True

  • __lt__ returns True iff __eq__ returns False and __le__ returns True

  • __le__ returns self._data <= type(self)(other)._data (modify __eq__ or __le__ as needed to change the behaviour of the other comparison methods)

BaseDict

Just like BaseList but for dict… The following methods are implemented: __contains__, __delitem__, __eq__, __format__, __ge__, __getitem__, __gt__, __hash__, __ior__, __iter__, __le__, __len__, __lt__, __or__, __repr__, __reversed__, __ror__, __setitem__, __str__, clear, copy, get, items, keys, pop, popitem, setdefault, update, values. The classmethods __class_getitem__ and fromkeys are not implemented.

OkayDict

A subclass of BaseDict with common sense implementations for further inheritance just like OkayList for BaseList.

BaseSet

Just like BaseSet but for set… The following methods are implemented: __and__, __contains__, __eq__, __format__, __ge__, __gt__, __hash__, __iand__, __ior__, __isub__, __iter__, __ixor__, __le__, __len__, __lt__, __or__, __rand__, __repr__, __ror__, __rsub__, __rxor__, __str__, __sub__, __xor__, add, clear, copy, difference, difference_update, discard, intersection, intersection_update, isdisjoint, issubset, issuperset, pop, remove, symmetric_difference, symmetric_difference_update, union, update. The classmethod __class_getitem__ is not implemented.

OkaySet

A subclass of BaseSet with common sense implementations for further inheritance just like OkayList for BaseList.

Installation

To install datahold, you can use pip. Open your terminal and run:

pip install datahold

License

This project is licensed under the MIT License.

Links

• Documentation

• Download

• Source

Credits

• Author: Johannes

• Email: [e-mail]

Thank you for using datahold!