我正在尝试创建一个动态函数来动态添加属性，以便轻松地在 jinja 模板中访问值。
此代码有效，但它是静态的。
# Used to display a cart summary of items that have been pledged.
products_in_cart = Cart.query.filter(Cart.campaign_id == campaign_id).all()
# total_cart_quantity(products_in_cart, "quantity", "quantity_total")
for item in products_in_cart:
item.quantity_total = 0 #Adding the attribute quantity_total
for item_loop2 in products_in_cart:
if item.user_id == item_loop2.user_id:
item.quantity_total = item.quantity_total + item_loop2.quantity
# Remove duplicate objects based on user_id attribute.
new_set = set()
new_list = []
for obj in products_in_cart:
if obj.user_id not in new_set:
new_list.append(obj)
new_set.add(obj.user_id)
products_in_cart = new_list
我想根据传入函数的参数使添加的属性名称动态化，以便我可以在其他地方使用。点符号不起作用，因为我需要一个变量来命名属性。 obj[variable_attrbute] 错误。 setattr() 什么都不做。
def total_cart_quantity(cart_objects, sum_attribute, new_attribute):
'''
From cart get the total of a particular quantity and add it to a new attribute.
cart_objects = the queried cart_objects.
sum_attribute = the attribute to be summed.
new_attribute = the string of the new attribute name
'''
for item in cart_objects:
# Two different attempts to add an attribute.
# setattr will just not add the attribute
setattr(item, sum_attribute, new_attribute) # this will do nothing
# item[new_attribute] = 0 # this will error
for item_loop2 in cart_objects:
if item.user_id == item_loop2.user_id:
item[new_attribute] = item[new_attribute] + item_loop2[sum_attribute]
# Remove duplicate objects based on user_id attribute.
new_set = set()
new_list = []
for obj in cart_objects:
if obj.user_id not in new_set:
new_list.append(obj)
new_set.add(obj.user_id)
products_in_cart = new_list
return products_in_cart
如何动态添加属性名称和值？
最佳答案
您正在使用 getattr和 setattr以错误的方式。实际签名如下:
variable = object.field ~ variable = getattr(object, 'field' [, default])
object.field = value ~ setattr(object, 'field', value)
关于Python如何将属性添加到函数中的现有对象，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/31620772/