safebag 0.1.7

Little python package implementing optional chaining

Safebag

Safebag is a little python package implementing optional chaining.

Installation

pip install safebag

Usage

chain [source]

Optional chain constructor

Optional chain constructed from any object.

Chain is used for building sequence of null-safe attribute calls.

from __future__ import annotations

import dataclasses as dt
import typing


@dt.dataclass
class Node:
    data: int
    node: typing.Optional[Node]


nodes = Node(data=1, node=Node(data=2, node=None))

from safebag import chain

third_node_proxy = chain(nodes).node.node.node
print(third_node_proxy)  # ChainProxy(data_object=None, bool_hook=False)

get_value [source]

Final value getter for optional chain.

Optional chain constructed from any object. Chain is used for building sequence of null-safe attribute calls.

from __future__ import annotations

import dataclasses as dt
import typing


@dt.dataclass
class Node:
    data: int
    node: typing.Optional[Node]


nodes = Node(data=1, node=Node(data=2, node=None))

from safebag import chain, get_value

third_node_proxy = chain(nodes).node.node.node
value = get_value(third_node_proxy)
assert value is None

next_node = chain(nodes).node
value = get_value(next_node)  # Node(data=2, node=None)

Useful in combination with walrus operator:

if next_node := chain(nodes).node.node:
    print(get_value(next_node))

if next_node := chain(nodes).node:
    print(get_value(next_node))  # Node(data=2, node=None)

ChainProxy [source]

ChainProxy container:

• stores data_object
• proxying data_object attribute value into new ChainProxy instance when attribute is invoked. If attribute does not exist or attribute value is None. ChainProxy instance data_object will be None and bool_hook will be False.
• ChainProxy instance always returning when attribute is invoked.