Python OOP：未定义变量。 范围问题是什么？

Question

The error message is as follows:

Traceback (most recent call last):
  File "./bitcoin_price.py", line 57, in <module>
    Coindesk()
  File "./bitcoin_price.py", line 45, in Coindesk
    coindesk.pass_for_request()
  File "./bitcoin_price.py", line 39, in pass_for_request
    get_price = BtcAPI(url, api_id, json_tree)
NameError: name 'url' is not defined

What am I missing, here? I'm guessing it is the coindesk.pass_for_request(), but I can't sort out exactly why the values don't get passed. Also, what is a good way to debug something like this? I'm having a rough time looking inside of the classes to see what is going on.

class Price:


    def __init__(self, api_id, url, json_tree):

        self.api_id = api_id
        self.url = url
        self.json_tree = json_tree

    def pass_for_request(self):

        get_price = BtcAPI(url, api_id, json_tree)
        get_price.btc_api_call()


def Coindesk():

    coindesk = Price(api_id ="coindesk", url = "https://api.coindesk.com/v1/bpi/currentprice.json", json_tree = "['time']['updated']")
    coindesk.pass_for_request()

Answer 1

Try to replace

get_price = BtcAPI(url, api_id, json_tree)

with

get_price = BtcAPI(self.url, self.api_id, self.json_tree)

Answer 2

There is no url or api_id variable in the scope of pass_for_request . You probably meant to access self.url and self.api_id , in python you have to use self. to access members unlike in other languages where using this. is optional.

Also another thing I spotted is when you're trying to create a Price in Coindesk you are passing in api_id and the other arguments as if they are arguments with defaults, which they are not. You'd need to call it as: Price("coindesk", "https://mylinktocoindesk", "['time']['updated']")

Here's some reading on OOP in python that you might find helpful: https://docs.python.org/3/tutorial/classes.html https://www.tutorialspoint.com/python/python_classes_objects.htm