Python类在实例化时缺少参数

Question

我有一个类user，它从sqlitedb文件中提取基于用户名的值。我仔细检查了一下，cursorexecute检索到了正确的元组，但是在实例化User类时似乎出现了问题。你知道吗

这是我的档案和照片

你知道吗用户.py你知道吗

import sqlite3


class User:
    # _id becuase id is a reserved keyword
    def __init__(self, _id, username, password):
        self.id = _id
        self.username = username
        self.password = password

    # added this since self wasn't used and we called User instantiation
    @classmethod
    def find_by_username(cls, username):
        connection = sqlite3.connect("data.db")
        cursor = connection.cursor()

        query = "SELECT * FROM users WHERE username=?"
        # execute has to be in the form of a tuple
        result = cursor.execute(query, (username,))
        # gets the first result in the set , and if empty returns None
        row = result.fetchone()
        if row:
            # this expands into row[0],row[1],row[2]
            user = cls(*row)
        else:
            user = None

        connection.close()
        return user

    @classmethod
    def find_by_id(cls, _id):
        connection = sqlite3.connect("data.db")
        cursor = connection.cursor()

        query = "SELECT * FROM users WHERE id=?"

        row = cursor.execute(query, (_id,))
        if row:
            user = cls(*row)
        else:
            user = None

        connection.close()
        return user

你知道吗安全.py你知道吗

from werkzeug.security import safe_str_cmp
from user import User


def authenticate(username, password):
    user = User.find_by_username(username)
    if user and safe_str_cmp(user.password, password):
        return user


def identity(payload):
    user_id = payload["identity"]
    return User.find_by_id(user_id)

我已经确认我的db呼叫用户.py返回正确的元组（id，“username”，“password”）。这是我得到的stacktrace：

 Traceback (most recent call last):
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 2309, in __call__
    return self.wsgi_app(environ, start_response)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 2295, in wsgi_app
    response = self.handle_exception(e)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask_restful/__init__.py", line 269, in error_router
    return original_handler(e)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 1741, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/_compat.py", line 34, in reraise
    raise value.with_traceback(tb)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 2292, in wsgi_app
    response = self.full_dispatch_request()
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 1815, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask_restful/__init__.py", line 269, in error_router
    return original_handler(e)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 1718, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/_compat.py", line 34, in reraise
    raise value.with_traceback(tb)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 1813, in full_dispatch_request
    rv = self.dispatch_request()
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/app.py", line 1799, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask_restful/__init__.py", line 458, in wrapper
    resp = resource(*args, **kwargs)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask/views.py", line 88, in view
    return self.dispatch_request(*args, **kwargs)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask_restful/__init__.py", line 573, in dispatch_request
    resp = meth(*args, **kwargs)
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask_jwt/__init__.py", line 176, in decorator
    _jwt_required(realm or current_app.config['JWT_DEFAULT_REALM'])
  File "not_importtant_path/venv/lib/python3.6/site-packages/flask_jwt/__init__.py", line 162, in _jwt_required
    _request_ctx_stack.top.current_identity = identity = _jwt.identity_callback(payload)
  File "not_importtant_path/code/security.py", line 13, in identity
    return User.find_by_id(user_id)
  File "not_importtant_path/code/user.py", line 40, in find_by_id
    user = cls(*row)
TypeError: __init__() missing 2 required positional arguments: 'username' and 'password'

Answer 1

在find_by_id类方法中，需要在cursor.execute()之后fetchone。您在find_by_username类方法中正确地做到了这一点。你知道吗