python - flask 中有没有办法获取 request.json 中的每个对象并将每个属性保存在模型上？

Question

我有以下冗长的代码，它设置 request.json['example'] 中的每个变量，然后保存模型 Inventory。有没有办法用更少的代码来做到这一点？例如，在 ruby​​ 中，我可以简单地将参数传递给 Inventory(inventory_params)。

@api.route('/new/<id>', methods=['POST'])
@cross_origin()
def new_item(id):
    date_opened = None
    date_expired = None
    received_date = None
    order_date = None
    if len(request.json['opened']) >= 1:
        date_opened = datetime.strptime(request.json['opened'], '%m/%d/%Y')
        print(date_opened)
    if len(request.json['expiration_date']) >= 1:
        date_expired = datetime.strptime(request.json['expiration_date'], '%m/%d/%Y')
    if len(request.json['received_date']) >= 1:
        received_date = datetime.strptime(request.json['received_date'], '%m/%d/%Y')
    if len(request.json['order_date']) >= 1:
        order_date = datetime.strptime(request.json['order_date'], '%m/%d/%Y')
    amount=request.json['amount']
    units=request.json['units']
    location=request.json['location']
    opened=request.json['opened']
    lot=request.json['lot']
    batch=request.json['batch']
    notes=request.json['notes']
    price=request.json['price']
    country_code=request.json['country_code']
    secondary_location=request.json['secondary_location']
    vendor_code=request.json['vendor']
    uid = request.json['uid']
    item = Inventory(vendor_code=vendor_code, country_code=country_code, price=price, secondary_location=secondary_location, lot=lot, original_amount=amount, amount=amount, original_units=units, units=units, location=location, plant_material_id=id, uid=uid, batch=batch, notes=notes, date_opened=date_opened, date_expired=date_expired, received_date=received_date, order_date=order_date )
    db.session.add(item)
    db.session.commit()
    return jsonify({'results': True})

Answer 1

您可以使用 argument unpacking为此。

基本原则是，如果你有一个接受关键字参数的函数或方法，比如

def foo(bar=42, qux=None):
    pass

您可以不用像 foo(bar=1, qux=23) 那样调用它，而是从字典中获取这些参数，然后通过解包将它们传递给函数(这就是 ** 语法的作用):

kwargs = {'bar': 1, 'qux': 23}

foo(**kwargs)

---

因为在您的情况下，requests.json 中的键/值与Inventory 的构造函数所需的参数之间没有严格的 1:1 关系，您将需要对这些值进行一些预处理，因此

• 处理后从参数字典中删除原始值
• 使用正确的键将处理后的值添加到参数字典中

构建参数字典后，Inventory(**params) 会将所有这些参数传递给 Inventory.__init__()，因此您需要确保匹配方法的签名。

这是一个独立的示例(没有 Flask 或 SQLAlchemy，但它确实没有区别):

from datetime import datetime


params = {
    'opened': '05/07/2015',
    'vendor_code': 'VC',
    'country_code': 'US',
}


class Inventory(object):
    def __init__(self, vendor_code=None, country_code=None, date_opened=None):
        self.vendor_code = vendor_code
        self.country_code = country_code
        self.date_opened = date_opened

    def __repr__(self):
        return repr(self.__dict__)


def create_inventory(params):
    # Deal with a raw value that needs to be processed
    date_opened = None
    if len(params['opened']) >= 1:
        date_opened = datetime.strptime(params['opened'], '%m/%d/%Y')

    # Remove the raw value from the params dict
    params.pop('opened')

    # Add the processed value to the `params` dict with the proper key
    params['date_opened'] = date_opened

    # All the other parameters get passed through unmodified
    inv = Inventory(**params)
    return inv

print create_inventory(params)