Send dictionary parameters to class method called inside __init_

I want to enhance the following artificial example

class Record:
    def __init__(self, data):
        self.data = data

    def filter(self, positive = False, even = False):
        data_ = self.data
        if positive:
            data_ = [c for c in data_ if c>0]
        if even:
            data_ = [c for c in data_ if c % 2 ==0]
        self.data = data_

data = list(range(-5,10,1))
record = Record(data)
record.filter(positive=True, even=True)
print(record.data)

which prints correctly [2,4,6,8], so that it would be possible to request filtering upon initialisation of the Record instance. My approach is

class Record:
    def __init__(self, data, filter = {}):
        self.data = data
        if len(filter) > 0:
            self.filter(**filter)


    def filter(self, positive = False, even = False):
        data_ = self.data
        if positive:
            data_ = [c for c in data_ if c>0]
        if even:
            data_ = [c for c in data_ if c % 2 ==0]
        self.data = data_

data = list(range(-5,10,1))
record = Record(data,filter={positive:True, even:True})
print(record.data)

and (naturally...) I get the error NameError: name 'positive' is not defined.

How to proceed here, and also is it, in general, a right idea to embed a method into initialisation?

CodePudding user response：

You don't have to create a dictionary to pass the arguments. This would work too:

class Record:
    def __init__(self, data, **args):
        self.data = data
        self.filter(**args)
    def filter(self, positive=False, even=False):
        ...

f1 = Record(data)    # both positive and even will be False
f2 = Record(data, positive=True)
f3 = Record(data, even=True)
f4 = Record(data, even=True, positive=True)

This has the added benefit that you treat even and positive consistently throughout your code, avoiding having to quote them as strings at some points.