Python 2.7 / App Engine - TypeError: is_valid() takes exactly 2 arguments (3 given)

Question

The following code is close to what I am using without getting too long. I get the error TypeError: is_valid() takes exactly 2 arguments (3 given). To my eyes I am only passing 2 arguments. So where is the third argument coming from?

models/MyModel.py

from google.appengine.ext import db

class MyModel(db.model):
    a = db.StringProperty(required=True)
    b = db.StringProperty(required=True)
    c = db.StringProperty(required=True)

class Update:
    def is_valid(x, y)
        myquery = db.GqlQuery('SELECT * FROM Valid WHERE value = :1' x)
        v = myquery.get()

        if v.something == y:
            yet_more_stuff
            return(True)
        else:
            return(False)

controllers/WebHandler.py

import webapp2
from models.MyModel import Update

class WebHandler(webapp2.RequestHandler):
    def get(self):
        var_x = "string"
        var_y = "string"
        z = Update()
        if z.is_valid(var_x, var_y): <----- line error occurs
            do_some_stuff
        else
            do_some_other_stuff

It is probably something simple but after coding for 18 hours today my brain has turned into oatmeal.

Answer 1

将代码更改为 def is_valid(self, x, y)

Answer 2

解

你有两个解决方案:

• 在方法定义中添加一个表示实例的参数(将其命名self为一致性)或
• staticmethod在方法上使用装饰器.

说明和例子

这一行:

def is_valid(x, y):

表示调用方法时,x是类实例并且y是参数.如果你想接受两个参数(和实例本身),你的行应该是这样的:

def is_valid(self, x, y)

但是因为你没有对实例本身做任何操作,你也可以使用staticmethod装饰器:

@staticmethod
def is_valid(x, y):

这将删除在参数中传递的实例,您将只接收剩余的参数.