CODEWITHSUNDEEP
python
user1638532
user1638532

Reputation:

reinitialize an object with self.__init__(...)

Could anybody explain whether it is safe to reinitialize an object by calling "self.init(". as shown in the following simplified example?

The reason i'm asking is that i couldn't find this method neither in several python books nor in internet. There are some who suggest to list all attributes and set them to initial value one by one. Basically i want to set my object to initial state after it has finished some tasks.

class Book(object):
    def __init__(self,name,author):
        self.name = name
        self.author = author
        self.copies = 5

    def reset(self):
        self.__init__(self.name,self.author)

    def incrementCopy(self):
        self.copies += 1

Kite = Book('kite runner','khaled hosseini')

print 'initial number of copies:', Kite.copies
Kite.incrementCopy()
Kite.incrementCopy()
Kite.incrementCopy()
print '3 copies are added:', Kite.copies
Kite.reset()
print 'number of copies are reinitialized', Kite.copies


initial number of copies: 5
3 copies are added: 8
number of copies are reinitialized 5

Upvotes: 40

Views: 52402

Answers (3)

user10369452
user10369452

Reputation: 81

I consider is not unsafe, I have used it and nothing strange happens in the memory, but take into account that attributes defined in other methods will not be reset. Consider for example:

class Dummy:
    def __init__(self):
        self.x = 4
    def plus_one(self):
        self.x += 1
    def define_other_variables(self):
        self.y = 3
    def reset(self):
        self.__init__()
D = Dummy()
print(D.x) # 4
# print(D.y) will raise an AttributeError
D.plus_one()
D.plus_one()
# D.y do not exist
D.define_other_variables()
# D.y exist
print(D.x) # 6
D.reset()
print(D.x) # 4
print(D.y) # 3, still exist!!

Then, just remember to define every object in the init function. you could consider bad practice for this reason but I still think is elegant.

Upvotes: 7

Andrew Clark
Andrew Clark

Reputation: 208615

The only thing special about __init__ is that it is called automatically when an instance is created. Other than that it is a normal method, and it is safe to use it to set your object back to its initial state.

That being said, just because it is safe doesn't mean it is a good idea. Other people looking at your code might be confused by it, and it isn't difficult to do everything in a reset method (that __init__ can even call) to be more explicit about how the method is being used.

Upvotes: 42

Code Painters
Code Painters

Reputation: 7275

I would consider it a very bad practice - you should not __init__ manually (unless calling __init__ of the parent class). Also, passing object's data back to __init__ is somewhat strange.

Why not something like this:

class Book(object):
    def __init__(self,name,author):
        self.name = name
        self.author = author
        self.reset()

    def reset(self):
        self.copies = 5

Upvotes: 33

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