Search code examples
pythoncoding-style

Javascript style dot notation for dictionary keys unpythonic?


I've started to use constructs like these:

class DictObj(object):
    def __init__(self):
        self.d = {}
    def __getattr__(self, m):
        return self.d.get(m, None)
    def __setattr__(self, m, v):
        super.__setattr__(self, m, v)

Update: based on this thread, I've revised the DictObj implementation to:

class dotdict(dict):
    def __getattr__(self, attr):
        return self.get(attr, None)
    __setattr__= dict.__setitem__
    __delattr__= dict.__delitem__

class AutoEnum(object):
    def __init__(self):
        self.counter = 0
        self.d = {}
    def __getattr__(self, c):
        if c not in self.d:
            self.d[c] = self.counter
            self.counter += 1        
        return self.d[c]

where DictObj is a dictionary that can be accessed via dot notation:

d = DictObj()
d.something = 'one'

I find it more aesthetically pleasing than d['something']. Note that accessing an undefined key returns None instead of raising an exception, which is also nice.

Update: Smashery makes a good point, which mhawke expands on for an easier solution. I'm wondering if there are any undesirable side effects of using dict instead of defining a new dictionary; if not, I like mhawke's solution a lot.

AutoEnum is an auto-incrementing Enum, used like this:

CMD = AutoEnum()

cmds = {
    "peek":  CMD.PEEK,
    "look":  CMD.PEEK,
    "help":  CMD.HELP,
    "poke":  CMD.POKE,
    "modify": CMD.POKE,
}

Both are working well for me, but I'm feeling unpythonic about them.

Are these in fact bad constructs?


Solution

  • This is a simpler version of your DictObj class:

    class DictObj(object):
        def __getattr__(self, attr):
            return self.__dict__.get(attr)
    
    >>> d = DictObj()
    >>> d.something = 'one'
    >>> print d.something
    one
    >>> print d.somethingelse
    None
    >>>