在迭代“for-loop”时设置字典值

Question

我正在尝试创建一个嵌套字典，其中包含一组从 for 循环中提取的值，以衡量各种客户-产品配对的增长和收入金额。但是，当我遍历数据框以设置字典的元素时，每个字典元素最终都具有相同的值。这是怎么回事？

我已经尝试过更改列表构建方式的各种元素，但无济于事。

'''
TP_Name = customer name

Service_Level_1 = service name

100.2014 is just a marker to show that someone has started consuming the service

tpdict is already created with necessary nesting below with empty values at each endpoint
'''

for col in pivotdf.columns:
  growthlist = []
  amountlist = []
  first = True
  TP_Name, Service_Level_1 = col.split('___')
  for row in pivotdf[col]:
    if first == True:
      past = row+.00001
      first = False
    if row == 0 and past <.0001 :
      growth = 0
    elif row != 0 and past == .00001:
      growth = 100.2014
    else:
      current = row
      growth = (current-past)/past
    growth = round(growth,4)
    growthlist.append(growth)
    past = row +.00001
    amountlist.append(row)
  tpdict[TP_Name][Service_Level_1]['growth'] = growthlist
  tpdict[TP_Name][Service_Level_1]['amount'] = amountlist

'''
problem: Each value ends up being the same thing
'''

Expected results:

{'CUSTOMER NAME': {'PRODUCT1': {'growth': [unique_growthlist],   'amount': [unique_amountlist]},  'PRODUCT2': {'growth': [unique_growthlist],'amount': [unique_amountlist]}}}

Answer 1

字典是一个键值对（我相信你可能知道）。如果您尝试使用字典中已存在的键写入字典，则字典将覆盖该键的值。

示例：

d = dict()
d[1] = 'a' # d = {1: 'a'}
d[1] = 'b' # d = {1: 'b'}

您的项目似乎可以很好地使用 python 中的namedtuple。 namedtuple 基本上是一个轻量级的类/对象。 我的示例代码可能是错误的，因为我不知道您的 for 循环是如何工作的（评论对每个人都有帮助）。这里所说的只是一个例子。

我只提出这个建议，因为 dictionaries 消耗的内存比它们所持有的对象多约 33%（尽管它们要快得多）。

from collections import namedtuple

Customer = namedtuple('Customer', 'name products')
Product = namedtuple('Product', 'growth amount')

customers = []
for col in pivotdf.columns:
    products = []
    growthlist = []
    amountlist = []
    first = True
    TP_Name, Service_Level_1 = col.split('___')
    for row in pivotdf[col]:
        if first == True:
            past = row + .00001
            first = False
        if row == 0 and past < .0001 :
            growth = 0
        elif row != 0 and past == .00001:
            growth = 100.2014
        else:
            current = row
            growth = (current - past) / past
        growth = round(growth, 4)
        growthlist.append(growth)
        past = row + .00001
        amountlist.append(row)

    cur_product = Product(growth=growthlist, amount=amountlist) # Create a new product
    products.append(cur_product) # Add that product to our customer

# Create a new customer with our products
cur_customer = Customer(name=TP_Name, products=products)
customers.append(cur_customer) # Add our customer to our list of customers

这里的customers 是客户namedtuples 的列表，我们可以将其用作对象。 例如，我们可以这样打印出来。

for customer in customers:
    print(customer.name, customer.products) # Print each name and their products
    for growth, amount in customer.products:
        print(growth, amount) # Print growth and amount for each product.