CODEWITHSUNDEEP
pythonpython-2.7class
RDizzl3
RDizzl3

Reputation: 846

Assign Global Variable Inside Class From Class Variable

I have a question about classes in Python. I have create a class that looks something like this:

class Model(Object):

    __table__ = 'table_name'

    def func():

    def func2():

The table name is a global variable that the functions feed off of. I am trying to add old data so I would like to change the table name depending on if I am filling in from old information, so this is what I tried. 

class Model(Object):

    def __init__(self, backfill = False):
         self.backfill = backfill

    if self.backfill:
         __table__ = 'table_name'
    else:
         __table__ = 'table_name2'

    def func():

    def func2():

The final call would be something like this:

if backfill:
     model = Model(True).func()
else:
     model = Model.func()

Then I realized this wouldn't work because I cannot call self.backfill from outside the class definitions. I even tried creating a definition and calling that inside the class but that did not work either.

My question is:

  1. Is there a way to initialize the global variable inside the class from the class variables? Or is there a better way to do this in general?

Upvotes: 1

Views: 1554

Answers (1)

Frodon
Frodon

Reputation: 3775

__table__ is a class variabe, which means you can access it from an instance or from the class itself. You can update any instance value according to the value of backfill in the __init__ method:

class Model(Object):
    __table__ = 'table_name'
    def __init__(self, backfill = False):
        self.backfill = backfill
        if self.backfill:
            self.__table__ = 'table_name2'

Then to create an instance, just give the backfill parameter to the constructor, without any if/else statement:

print(Model.__table__)
# table_name
backfill = True
model = Model(backfill)
print(model.__table__)
# table_name2

But I don't see the point of using a class variable in your case. You can just define it in the __init__ method:

class Model(Object):
    def __init__(self, backfill = False):
        self.backfill = backfill
        self.__table__ = 'table_name'
        if self.backfill:
            self.__table__ = 'table_name2'

Upvotes: 2

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