CODEWITHSUNDEEP
pythondictionaryobject
Nazmul Hasan
Nazmul Hasan

Reputation: 7040

python dictionary key Vs object attribute

suppose i have object has key 'dlist0' with attribute 'row_id' the i can access as

getattr(dlist0,'row_id')

then it return value but if i have a dictionary 

ddict0 = {'row_id':4, 'name':'account_balance'}
getattr(ddict0,'row_id')

it is not work

my question is how can i access ddict0 and dlist0 same way

any one can help me?

Upvotes: 6

Views: 4522

Answers (3)

djvg
djvg

Reputation: 14255

Although similar to @Amber's answer, the following is slightly more concise, and allows us to specify a default value. Gets either a dict item or an object attribute:

def get(*args):
    _get = dict.get if type(args[0]) is dict else getattr
    return _get(*args)

The arguments for dict.get and getattr are similar. Both accept an optional default value. Note, however, that getattr raises an error if the attribute does not exist and default is not explicitly specified.

Some trivial examples:

>>> get({'my_key': 'my_value'}, 'my_key')
'my_value'

>>> class MyClass(object): pass
...
>>> get(MyClass(), 'my_attr_name', 'missing')
'missing'

Upvotes: 0

Amber
Amber

Reputation: 526583

Dictionaries have items, and thus use whatever is defined as __getitem__() to retrieve the value of a key.

Objects have attributes, and thus use __getattr__() to retrieve the value of an attribute.

You can theoretically override one to point at the other, if you need to - but why do you need to? Why not just write a helper function instead:

Python 2.x:

def get_value(some_thing, some_key):
    if type(some_thing) in ('dict','tuple','list'):
        return some_thing[some_key]
    else:
        return getattr(some_thing, some_key)

Python 3.x:

def get_value(some_thing, some_key):
    if type(some_thing) in (dict,tuple,list):
        return some_thing[some_key]
    else:
        return getattr(some_thing, some_key)

Upvotes: 9

John La Rooy
John La Rooy

Reputation: 304147

Perhaps a namedtuple is more suitable for your purpose

>>> from collections import namedtuple
>>> AccountBalance=namedtuple('account_balance','row_id name')
>>> ddict0=AccountBalance(**{'row_id':4, 'name':'account_balance'})
>>> getattr(ddict0,'row_id')
4

>>> ddict0._asdict()
{'row_id': 4, 'name': 'account_balance'}

Upvotes: 1

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