JSON to shell

json_to_shell.py

import json
import pipes


def shell(json_input):
    """ Flattens a JSON-dict as a list of key-value pairs.

    For each key/value of the dictionary:
    - "Simple" elements (strings, bools, integers) are represented as a string
      "KEY=value". pipes.quote is used to handle escaping.
    - Lists are represented as a string "KEY=n" where n is the number of
      elements in the list, then with one line per element "KEY_n=value" where
      n is the index of the element.
    - Dictionaries are represented as a string "KEY=a b c" where a, b, c are
      the keys of the dictionary, then with one line per element "KEY_X=value"
      where X is the dictionary key.

    Example:

    >>> shell({
    ...     'hello': 'world',
    ...     'complex': 'value with spaces',
    ...     'list': ['one', 'two'],
    ...     'dict': {
    ...         'first': 'value',
    ...         'second': 'value with spaces',
    ...         'third': ['x', 'xx', 'xxx']
    ...     }
    ... })
    HELLO=world
    COMPLEX='value with spaces'
    LIST=2
    LIST_0=one
    LIST_1=two
    DICT='FIRST SECOND THIRD'
    DICT_FIRST=value
    DICT_SECOND='value with spaces'
    DICT_THIRD=3
    DICT_THIRD_0=x
    DICT_THIRD_1=xx
    DICT_THIRD_0=x
    DICT_THIRD_1=xx
    DICT_THIRD_2=xxx
    """
    def _transform_line(key, value):
        """ Transforms a single line (simple type, list or dict).
        """
        def make_key(key):
            """ Makes keys uppercase. """
            return key.upper()

        if isinstance(value, dict):
            # KEY=a b c
            out = '%s=%s\n' % (
                make_key(key),
                pipes.quote(' '.join(make_key(key) for key in value.keys()))
            )
            for elem_key, elem_value in value.items():
                out += _transform_line(
                    make_key('%s_%s' % (key, elem_key)),
                    elem_value
                )
            return out

        elif isinstance(value, list):
            # KEY=n
            out = '%s=%s\n' % (make_key(key), len(value))
            for idx, elem in enumerate(value):
                out += _transform_line(make_key('%s_%s' % (key, idx)), elem)
            return out

        elif value is None:
            # KEY=
            return '%s=\n' % make_key(key)

        # pipes.quote doesn't accept integers or bools.
        value = str(value)
        return '%s=%s\n' % (make_key(key), pipes.quote(value))

    json_input = ''.join(
        _transform_line(key, value)
        for key, value in json.loads(json_input).items()
    )
    return json_input


print(shell(json.dumps({
    'key': ['one', 'two', {'three': 'x', 'three_bis': 3}]
})))