Python; working with instance variable created by a method

Question

Im a bit of a beginner when it comes to classes.

I have a class defined as follows (simplified for purposes of this post)

class worksheet:
    def __init__(self, filename):
        self.filename = (filename).strip().replace(" ","")
    def idMaker(self):
        number = '{:05d}'.format(random.randrange(1,99999))
        sheetId = self.filename+str(number)

I want to be able to get the 'sheetID' for each instance by saying something like the following (again, this might be completely incorrect):

newSheet = worksheet('testsheet')
id = newSheet.sheetID

This of course does not work, but I am not sure what I need to do to make it work.

I want to make sure the ID stays constant and doesnt recreate itself with new random numbers.

Thank you in advance

sxn · Accepted Answer · 2017-02-14 17:49:06Z

2

Just generate and assign the id in __init__. In general, as a user of the class, you don't want to care about generating the id yourself. As far as you're concerned, instantiating Worksheet gives you a complete, usable object.

import random

class Worksheet(object):
    def __init__(self, filename):
        self.filename = filename.strip().replace(' ','')

        number = '{:05d}'.format(random.randrange(1,99999))
        self.sheet_id = self.filename + str(number)

sheet = Worksheet(' some filename with spaces ')
print(sheet.filename)
print(sheet.sheet_id)

will output

somefilenamewithspaces
somefilenamewithspaces68237

edited Feb 14, 2017 at 17:49

answered Feb 14, 2017 at 17:39

sxn

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Comments

Aaron · Accepted Answer · 2017-02-14 17:31:08Z

0

The sheetId variable lives within that class's idMaker method, so you cannot access it with a dot operator. If you are trying to create custom IDs for instances of your class, I would recommend doing that in the class constructor __init__ method so it gets assigned on object creation. Maybe consider the following:

class worksheet:
    def __init__(self, filename):
        self.filename = (filename).strip().replace(" ","")
        number = '{:05d}'.format(random.randrange(1,99999))
        self.sheetID = self.filename+str(number)

edited Feb 14, 2017 at 17:31

answered Feb 14, 2017 at 17:28

Aaron

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2 Comments

Moses Koledoye Over a year ago

Not quite right. A new random number is generated with each call, and that does not make for an id

Aaron Over a year ago

@MosesKoledoye Yea, I'll strike that from my initial answer. I didn't catch that on my first time through the question.

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