Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Welcome To Ask or Share your Answers For Others

Categories

0 votes
295 views
in Technique[技术] by (71.8m points)

python - Creating class instance from dictionary?

I am trying to create class instance from dictionary that has keys more than class has attributes. I already read answers on the same question from this link: Creating class instance properties from a dictionary?. The problem is that I can't write __init__ in class definition as I want, because I'm using SQLAlchemy declarative style class definition. Also type('className', (object,), dict) creates wrong attributes that are not needed. Here is the solution that I found:

dict = {'key1': 'value1', 'key2': 'value2'}
object = MyClass(**dict)

But it does not work if dict has redundant keys:

dict = {'key1': 'value1', 'key2': 'value2', 'redundant_key': 'redundant_value'}
object = MyClass(**dict) # here need to ignore redundant_key

Are there any solutions except direct deleting all redundant keys from dict?

See Question&Answers more detail:os

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
Welcome To Ask or Share your Answers For Others

1 Reply

0 votes
by (71.8m points)

Use a classmethod to filter the dict and return the object.

You then dont have to force your __init__ method to accept a dict.

import itertools

class MyClass(object):
    @classmethod
    def fromdict(cls, d):
        allowed = ('key1', 'key2')
        df = {k : v for k, v in d.iteritems() if k in allowed}
        return cls(**df)

    def __init__(self, key1, key2):
        self.key1 = key1
        self.key2 = key2

dict = {'key1': 'value1', 'key2': 'value2', 'redundant_key': 'redundant_value'}

ob = MyClass.fromdict(dict)

print ob.key1
print ob.key2

与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…
OGeek|极客中国-欢迎来到极客的世界,一个免费开放的程序员编程交流平台!开放,进步,分享!让技术改变生活,让极客改变未来! Welcome to OGeek Q&A Community for programmer and developer-Open, Learning and Share
Click Here to Ask a Question

...