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Python Object-Oriented Python (retired) Objects Create a Class with a Method

Posted by Wilfredo Casas
Wilfredo Casas
6,174 Points

What's wrong with my code?

Also, I'm not sure about the placeholder meaning

method.py 
class Store():
  open = 4
  close = 8

  def hours():
    return "We're open from {} to {}.".format(open, close)

2 Answers

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

You are very close. You need to add the "self" reference for methods and attributes:

class Store():
    open = 4
    close = 8

    def hours(self):
        return "We're open from {} to {}.".format(self.open, self.close)
Jason Anders
MOD
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

Hey Wilfredo,

You're on the right track, but there are a couple things.

  1. When creating a Class, it does not take any parameters so shouldn't have () after it, you just need the colon.

Edited

  1. Now the method inside the Class needs a parameter (usual convention is self).

Answer edited to correct error

class Store:
  open = 4
  close = 8

  def hours(self):
    return "We're open from {} to {}.".format(self.open, self.close)

Hopefully this makes sense. Keep Coding! :dizzy:

Wilfredo Casas
Wilfredo Casas
6,174 Points

Thanks Jason, but is the self not necessary in the method of class? or does this version give me the same result?

Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

You know, it's been a while since I've worked with Python, so this may be a question Chris Freeman can help with.

I did test the code I provided in the challenge, and it passed, but after reading Chris' answer, I'm actually not sure myself. Sorry.

Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

While the parens after the class name are not required, it is common to use them as a visual cue that no inheritance (other than from the default object) is defined.

Bound functions to classes (aka methods) require a first parameter to represent the bound instance or class. This can be named anything, but, again for visual cues, self is used for instance methods and cls is used for classmethods.

An alternative way to code the method hours() would be to pass the default class attribute values for open and close in the parameter list. While this will pass the challenge it is likey not what you want.

class Store:
    open = 4
    close = 8
    # add first parameter self and class attributes as defaults
    def hours(self, open=open, close=close):
        return "We're open from {} to {}.".format(open, close)

The default values for open and close are set at compile time, so "4" and "8" become the defaults even if open and close change:

# instantiate a new store
>>> s1 = Store()
# deg default hours
>>> s1.hours()
"We're open from 4 to 8."
# call hours with arguments
>>> s1.hours(1, 9)
"We're open from 1 to 9."
# set new hours
>>> s1.open = 9
>>> s1.close = 5
# verify hours
>>> s1.open
9
>>> s1.close
5
>>> 
# check hours method. Still has predefined results
>>> s1.hours()
"We're open from 4 to 8."

By choosing to useself.open and self.closeas arguments toformat()` the current value of these attributes will be used in the print.

Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,454 Points

Jason, your posted code did not pass Task 2 when I tried it.

Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

Thank you very much Chris. :smiley:

I edited my answer to correct the errors you pointed out. Again, thank-you for responding and for the detailed explanation (it's kind of coming back to me now). It was very helpful and very much appreciated.

:dizzy: