safe_dict.py

"""
# / is field access.
# .get() is unwrapping value.

# Invalid field access is ignored and returns None.
>>> (Wrap(1) / 'a' / 0 / 'b').get()

# You may specify default value in case invalid field was accessed.
>>> (Wrap(1) / 'a' / 0 / 'b').get(True)
True

>>> (Wrap([1, 2, {'fields': {'body': [{'fields': {'a': 'hello'}}]}}]) / 2 / 'fields' / 'body' / 0 / 'fields' / 'a').get()
'hello'
"""

class UnitWrap:
    def __truediv__(self, other):
        return self

    def get(self, default=None):
        return default


class Wrap:
    def __init__(self, x):
        self._x = x

    def __truediv__(self, other):
        try:
            return Wrap(self._x[other])
        except (KeyError, TypeError, IndexError):
            return UnitWrap()

    def get(self, default=None):
        return self._x
      
      
if __name__ == "__main__":
    import doctest

    doctest.testmod()