safitty 0.3.1

Safitty. Wrapper on JSON/YAML configs for Python.

Safitty

Safitty is a wrapper on JSON/YAML configs for Python. Designed with a focus on the security of get/set operations for deep-nested dictionaries and lists.

Installation

Currently only submodule installation is available

git submodule add https://github.com/TezRomacH/safitty.git safitty

Features

• Safe get for dictionaries and lists
• Nested keys at one time
• Several strategies

Usage

Suppose you have a configuration file looks like:

verbose: false

status: 1

paths:
  jsons:
    - first
    - second
    - third
  images: important/path/to/images/

transforms:
  - name: Normalize
    function: ToTensor
    params: null
  -
    name: Padding
    function: Pad
    params:
      fill: 3
      padding_mode: reflect

Maybe it's located at your project folder or you receive it from a server. For now we want to load the config and get some of the nested keys

import safitty as sf
import yaml


with open("path/to/config.yml") as stream:
    config = yaml.load(stream)

param = sf.safe_get(config, 'paths', 'images')
# param == 'important/path/to/images/'

Python's dict will throw an error if we try to get a non-existing path. Or it will turn into a disgusting construction.

# usual way to work with dict

>>> config['transforms'][1]['param']['fill'] # oops, we wrote `param` insted of `params
KeyError: 'param'

>>> config.get('transforms')[1].get('param').get('fill') # What if we go deeeeeeper
AttributeError: 'NoneType' object has no attribute 'get'

>>> config.get('transforms')[1].get('params').get('fill') # it works, but looks awful
3

Anyway this last way doesn't help us with lists. Standard Python library doesn't provide safe get method for type list

>>> config.get('transforms')[2].get('params').get('fill') # wrong index
IndexError: list index out of range

Solution here is to use Saffity:

>>> sf.safe_get(config, 'transforms', 2, 'params', 'fill')
# None

>>> sf.safe_get(config, 'transforms', 1, 'params', 'fill')
3

>>> sf.safe_get(config, 'transforms', 2, 'values', 'fill', default=42)
42

With Safitty you'll not be scared about nested depth

>>> sf.safe_get(config, 'transforms', 1, 'params', 'fill', 'what', 'if', 'we', 'go', 'deeper')
# None

>>> sf.safe_get(config, 'transforms', 3, "wrong_key", 55, 'params', 'go', 'deeper', default="This is default value")
This is default value

Safitty provides several strategies for using the default param.

>>> sf.safe_get(config, 'transforms', 0, 'values', strategy='missing_key', default=42)
42

>>> sf.safe_get(config 'transforms', 0, 'values', strategy='last_value', default=42)
{"name": "Normalize", "function": "ToTensor", "params": None}

1. For strategy final, it returns default if the final result on applying keys is None. Safitty uses it by default
2. For strategy missing_key, it returns default only if some key in keys doesn't exist in config.
3. Strategy last_value returns last non null value if exists
4. Strategy last_container returns last non null container if exists

Note the difference for final and missing_key strategies.

>>> sf.safe_get(config, 'transforms', 0, 'params', default='No value')
No value

>>> sf.safe_get(config, 'transforms', 0, 'params', strategy='missing_key', default='No value')
# return None, because there were not not-existing keys

# But if we make a mistake in keys 
>>> sf.safe_get(config, 'transforms', 23, 'params', strategy='missing_key', default='No value')
No value

# or
>>> sf.safe_get(config, 'transforms', 0, 'values', strategy='missing_key', default='No value')
No value

Saffity provides transform params. If it's not None, the result will be applied to this type or function.

>>> from pathlib import Path
>>> sf.safe_get(config, 'paths', 'images', transform=Path)
PosixPath('important/path/to/images/')

>>> sf.safe_get(config, 'status', transform=bool)
True

Lambdas are also supported

NOT_FOUND = 404
>>> sf.safe_get(config, 'status', transform=lambda x: x != NOT_FOUND)

True