Python - add comments to dictionary as a property-CodePudding

I want to assign comments to the key-value pairs in my dictionary, ideally in a way that I can access them directly. Since I'm new to manipulating classes, I only came this far:

class MyDict(dict):
    def __init__(self, *arg, **kwargs):
        super(MyDict, self).__init__(*arg, **kwargs)

mydict = MyDict()
mydict['first'] = 1
mydict['second'] = 2

Is there a way to add a comment to each of the key-value pairs so I can access them like

for key, value, comment in mydict.iteritems():
    print(key, value, comment)

for key, value in mydict.iteritems():
    print(key, value, key.comment)  # or value.comment

Any other way is also fine, as long as the comments are directly accessible (meaning not via indexing of lists or so).

CodePudding user response：

If you store (value, comment) pairs, for each pair you can use tuple unpacking in the for statement (note the parenthesis). Although, this is kind of contradicting your "non-indexing" request:


mydict[key] = (value, comment)

for key, (value, comment) in mydict.items():
    print(key, value, comment)

Edit: Following specifications in the comments:

You could subclass a dict, that has another dict containing the comments as a member. Every regular dictionary method is left as is, but a specific method is implemented to iterate over the items along with a comment. Comments are added by using the corresponding method add_comment. If you want to include the comments into the initialzation, while keeping full compatibility with regular dictionary construction more work needs to be put into the __init__ definition.

class MyCommentedDict(dict):
  def __init__(self, *args, **kwargs):
    super(MyCommentedDict, self).__init__(*args, **kwargs)
    self._comments = dict()

  def add_comment(self, key, comment):
    self._comments.update({key:comment})
  
  def commented_items(self):
    """ Returns a generator that yields triplets of (key, value, comment).
    For all entries without a provided comment `None` is returned as comment."""
    return ((key, value, self._comments.get(key, None))
             for key, value in self.items())

a_dict = MyCommentedDict({'color': 'blue', 'fruit': 'apple', 'pet': 'dog'})
a_dict.add_comment('color', 'This a is color')

for key, value in a_dict.items():
  print(key, value)

>>>color blue
>>>fruit apple
>>>pet dog

for key, value, comment in a_dict.commented_items():
  print(key, value, comment)

>>>color blue This a is color
>>>fruit apple None
>>>pet dog None