How do you use self when defining variables with a class in python

Question

I'm just learning to work with functions and now classes in python. The functions that i've created would work if they were not in a class, but now my objective is to create a class for them. It looks like I'm not understanding how self works. I've added it as a parameter for each function, however I'm running into NameError: name 'variable name' is not defined messages when calling the functions. What am I missing?

Here is the script myTokClassTst.py code in progress:

import time
import json
import jwt
import requests
from lib.jwksutils import rsa_pem_from_jwk

class TokenMgr():
    """An attempt to model a Token Manager"""

    def __init__(self):
        """Initialize token attributes as needed"""
        pass

    def get_kid(self, token):
        headers = jwt.get_unverified_header(token)
        if not headers:
            raise InvalidAuthorizationToken('missing headers')
        try:
            return headers['kid']
        except KeyError:
            raise InvalidAuthorizationToken('missing kid')


    def get_jwk(self, kid):
        with open('testkeys/jwks-keys', 'r') as az:
            jwks = json.load(az)
        for jwk in jwks.get('keys'):
            if jwk.get('kid') == kid:
                print ('This is the jwk:', jwk)
                return jwk
        raise InvalidAuthorizationToken('kid not recognized')


    def get_public_key(self, token):
        print ('Response from get_public_token:', rsa_pem_from_jwk(get_jwk(get_kid(token))) )
        return rsa_pem_from_jwk(get_jwk(get_kid(token)))


    def validate_jwt(self, jwt_to_validate):
        public_key = get_public_key(jwt_to_validate)
        #Hard coding these for now
        valid_audiences = ['abc123aa86-1f3a-4774-8bae-2704bff9f797'] 
        issuer = 'https://login.microsoftonline.com/99c77bbe-8598-4b85-9e51-1ca753fa50f2/v2.0'
        decoded = jwt.decode(jwt_to_validate,
                            public_key,
                            verify=True,
                            algorithms=['RS256'],
                            audience=valid_audiences,
                            issuer=issuer)
        print('This is decoded:', decoded)

I'm calling the function like so within a python shell:

$ python
Python 3.7.2 (tags/v3.7.2:9a3ffc0492, Dec 23 2018, 23:09:28) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import myTokClassTst as mytok
>>> idval = mytok.TokenMgr()
>>> idval.validate_jwt('eyJ0eXAiOiJKV1QiLCJhbGciOiJSUA')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\myTokClassTst.py", line 97, in validate_jwt
    public_key = get_public_key(jwt_to_validate)
NameError: name 'get_public_key' is not defined

You really need to put more effort into researching something basic like this before posting a question. Not only are there many duplicates and related questions on class definitions, but this is all clearly explained in the [official documentation / tutorial](https://docs.python.org/3/tutorial/classes.html) — juanpa.arrivillaga, Aug 26 '20 at 19:15

score 2 · Accepted Answer · answered Aug 26 '20 at 19:00

use self.get_public_keysince you are trying to call same class method. same for get_jwk and get_kid

final code:

import time
import json
import jwt
import requests
from lib.jwksutils import rsa_pem_from_jwk

class TokenMgr():
    """An attempt to model a Token Manager"""

    def __init__(self):
        """Initialize token attributes as needed"""
        pass

    def get_kid(self, token):
        headers = jwt.get_unverified_header(token)
        if not headers:
            raise InvalidAuthorizationToken('missing headers')
        try:
            return headers['kid']
        except KeyError:
            raise InvalidAuthorizationToken('missing kid')


    def get_jwk(self, kid):
        with open('testkeys/jwks-keys', 'r') as az:
            jwks = json.load(az)
        for jwk in jwks.get('keys'):
            if jwk.get('kid') == kid:
                print ('This is the jwk:', jwk)
                return jwk
        raise InvalidAuthorizationToken('kid not recognized')


    def get_public_key(self, token):
        print ('Response from get_public_token:', rsa_pem_from_jwk(self.get_jwk(self.get_kid(token))) )
        return rsa_pem_from_jwk(self.get_jwk(self.get_kid(token)))


    def validate_jwt(self, jwt_to_validate):
        public_key = self.get_public_key(jwt_to_validate)
        #Hard coding these for now
        valid_audiences = ['abc123aa86-1f3a-4774-8bae-2704bff9f797'] 
        issuer = 'https://login.microsoftonline.com/99c77bbe-8598-4b85-9e51-1ca753fa50f2/v2.0'
        decoded = jwt.decode(jwt_to_validate,
                            public_key,
                            verify=True,
                            algorithms=['RS256'],
                            audience=valid_audiences,
                            issuer=issuer)
        print('This is decoded:', decoded)

score 0 · Answer 2 · answered Aug 26 '20 at 19:03

0

get_public_key is an instance method. So you need to call it as such:

self.get_public_key

where self refers to the instance of the class (like this keyword)

answered Aug 26 '20 at 19:03

srv236

509
3
5

How do you use self when defining variables with a class in python

2 Answers2