Refering to class variables without creating an instance in Python

Question

I am writing a class which is basically a data structure to hold status codes and an associated dict with each status code. I want to call a method, providing a numeric status code and get a dictionary back.

class StatusCode(object):
    def __init__(self):
        self.codes  = {  0: { 'flag': "QEX_OK",      'message': "job successful"                                          },
                         1: { 'flag': "QEX_CMDLINE", 'message': "general cmd line syntax or semantic error"               }
             }
    @staticmethod
    def get_code(code):
        return self.codes[code]

How would I correctly achieve this?

Much thx.

Bill Lynch · Accepted Answer · 2015-01-09 14:11:50Z

4

Use @classmethod:

class StatusCode(object):
    codes  = {
            0: { 'flag': "QEX_OK",      'message': "job successful"                           },
            1: { 'flag': "QEX_CMDLINE", 'message': "general cmd line syntax or semantic error"},
            }

    @classmethod
    def get_code(cls, code):
        return cls.codes[code]

edited Jan 9, 2015 at 14:11

Bill Lynch

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answered Jan 9, 2015 at 14:10

Mikko Ohtamaa

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3 Comments

BenH Over a year ago

What is "cls" in this example?

jonrsharpe Over a year ago

@BenH it's the class object, analogous to the instance object self in instance methods.

Mikko Ohtamaa Over a year ago

It's a reference to StatusCode class object, like self is reference to a created object instance

NPE · Accepted Answer · 2015-01-09 14:10:06Z

2

How about:

class StatusCode(object):
    codes  = {0: { 'flag': "QEX_OK",      'message': "job successful"                                          },
              1: { 'flag': "QEX_CMDLINE", 'message': "general cmd line syntax or semantic error"               }
             }

    @staticmethod
    def get_code(code):
        return StatusCode.codes[code]

print StatusCode.get_code(1)

answered Jan 9, 2015 at 14:10

NPE

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1 Comment

BenH Over a year ago

Awesome this is what I needed.... I was messing around with init() and didn't need to. Much thx.

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