Question

I need to extract data from external source. I build a base clas with some structure. I need objects with type of myBase class but with a name which automatically describes how many times I iterate over the source. I build a class which stores this number and with a call method which returns the object I need. I can’t find a way to have a string as the name for the object but automatically differ every time I build new object.
I simplified the code for this example:

class myBase:
    def __init__(self):
        iteratedValue = None

class myIterator:
    def __init__(self):
        self.k = 0
    def __call__(self, s):
        self.k += 1
        self.name = 'myData' + str(self.k)
        # create an object named myData1, myData2 ...
        self.name = myBase() 
        self.name.iteratedValue = s 
        print '%s name is %s for k = %i' % (self.name, self.name.iteratedValue, self.k)

        # return object named myData1 type of myBase
        return self.name

def DataExtraction():
    # function to extract data form external source
    data = myIterator()
    data('Alice') 
    data('Ben') 

DataExtraction()

My output is:

<__main__.myBase instance at 0x7f261b6dc6c8> name is Alice for k = 1
<__main__.myBase instance at 0x7f261b6dc6c8> name is Ben for k = 2

I need to return an object with a specific name and I expect an output:

myData1 name is Alice for k = 1
myData2 name is Ben for k = 2

The original problem is much more complicated. I have external data and every time they come I want to extract some values from this data. Every time I am doing this I need an object to work with it but I need this object with different names because on the end I store them in dict for another methods. In other words I work with data and store my results in the object myData1 when the original data change I work with it again and store the results in myData2 etc. After all I need all myData objects and do statistics on them to see how the change. I do not have access to original data any more. I need automatic name convention for myData and the best if it will express iterator.

How can I have a string in place of self.name as the name for an object?

Answer 1

You’re already doing it with self.name = 'myData' + str(self.k). The problem is that you immediately overwrite it with self.name = myBase(). I’m not sure what you’re trying to do with that myBase(), but you probably want to separate it from the name. self.name can be either a string or a myBase object, but it can’t be both.

Perhaps you can do:

    self.name = 'myData' + str(self.k)
    self.base= myBase() 
    self.base.iteratedValue = s 
    print '%s name is %s for k = %i' % (self.name, self.baseiteratedValue, self.k)

This way you can have both the name and the “base”, as separate attributes self.name and self.base.

Alternatively, you can give the myBase class a __str__ method. This will affect what shows up when you use print on a myBase object. However, to do that you’ll have to pass in the desired name when you instantiate myBase, something like:

class myBase(object):
    def __init__(self, name, iteratedValue):
        self.name = name
        iteratedValue = iteratedValue
    def __str__(self):
        return self.name

class myIterator(object):
    def __init__(self):
        self.k = 0
    def __call__(self, s):
        self.k += 1
        name = 'myData' + str(self.k)
        self.name = myBase(name, s) 
        print '%s name is %s for k = %i' % (self.name, self.name.iteratedValue, self.k)

        # return object named myData1 type of myBase
        return self.name

I’m not sure which of these ways (or perhaps some other way) is what you’re looking for. What’s puzzling is that you are making the “name” of the object be a myBase instance. I’m not sure what you’re intending the “name” of your object to represent, but I wouldn’t usually expect an object’s name to be some other object.

Incidentally, it looks like you’re using Python 2, in which case you should define your class with class someClass(object). Including the object makes your classes new-style classes, which is basically what you always want.

Edit: If what you’re trying to do is actually create a variable called myData1 based on the string, so you can do myData('Alice') and then somehow magically have the variable myData1 refer to that object, the answer is “Don’t do that.” If you want to create a bunch of objects and access them in a structured way by numbers or other labels, use a list or a dictionary.