想用装饰器打开pymongo数据库连接

Question

@api.route('/api/get_contacts')
def get_contacts():
with pymongo.MongoClient(f"mongodb+srv://{mongo_username}:{mongo_password}@dev.glstt.mongodb.net/xxxx?retryWrites=true&w=majority") as document:

看太多了。我想把它变成：

@api.route('/api/get_contacts')
@mongo
def get_contacts():

问题是，我不是很懂装饰器。所以，这就是我到目前为止所做的：


def mongo(f):
    @wraps(f)
    def wrap (*args,**kwargs):
        with pymongo.MongoClient(f"mongodb+srv://{mongo_username}:{mongo_password}@dev.glstt.mongodb.net/xxx?retryWrites=true&w=majority") as document:

            return f(document)
        return wrap

不确定我需要做什么才能让装饰器在代码前添加 'with operator'，并传递 x，然后将文档返回给路由函数。

Answer 1

装饰器的工作原理基本上是用 decorator(function) 替换您的函数。例如：

@decorator
def my_function():
    pass

等于

def my_function():
    pass

my_function = decorator(my_function)

这意味着您可以 return 来自装饰器的可调用函数，每次您使用参数调用它时，它都会使用特定参数调用装饰函数。

例如：

import functools

def decorator(decorated_function):
    @functools.wraps(decorated_function) # This means that the function that returns from this decorator, "wrapper", will keep the decorated_function's name,  `__doc__` argument and more.
    def wrapper(*args, **kwargs):
        """
        Every time you will call the function that returned from the decorator, this function will be called with the particular arguments in args and kwargs.
        """
        return decorated_function(*args, **kwargs) + 10
    return wrapper


@decorator
def func(n):
    return n * 2

result = func(2) # here we called the function `wrapper`, the result is func(2) + 10, as we did when we called the function.

print(result) # 14

我们也可以 print(func) 结果会是这样的 <function func at 0x7f5eb16b0040>，如果我们不使用 functools.wraps：<function decorator.<locals>.wrapper at 0x7fba9ba0f040>.

现在回答你的问题，当你堆叠装饰器时，

@c
@b
@a
def func(): pass

顺序是 c(b(a(func))) 因此，名为 mongo 的函数应该从 api.route('/api/get_contacts') 获取参数“request”。（我不知道这是什么框架，所以我无法预测这个框架是否将请求作为函数参数提供）。

如果框架不将请求作为参数传递：

def mongo(f):
    @functools.wraps(f)
    def wrap():
        with pymongo.MongoClient(f"mongodb+srv://{mongo_username}:{mongo_password}@dev.glstt.mongodb.net/xxx?retryWrites=true&w=majority") as document:
            return f(document)
    return wrap

如果是：

def mongo(f):
    @functools.wraps(f)
    def wrap(request):
        # do something with the request
        with pymongo.MongoClient(f"mongodb+srv://{mongo_username}:{mongo_password}@dev.glstt.mongodb.net/xxx?retryWrites=true&w=majority") as document:
            return f(document)
    return wrap

然后它允许你这样做：

@api.route('/api/get_contacts')
@mongo
def get_contacts(document):
    pass

想用装饰器打开pymongo数据库连接

Looking to open pymongo database connection with decorator

python

flask

pymongo

decorator

python-decorators