Предположим, у меня есть следующий код, который вычисляет, сколько продуктов я могу купить с учетом моего бюджета:

import math
import pandas as pd

data = [['2021-01-02', 5.5], ['2021-02-02', 10.5], ['2021-03-02', 15.0], ['2021-04-02', 20.0]]
df = pd.DataFrame(data, columns=['Date', 'Current_Price'])

df.Date = pd.to_datetime(df.Date)
mn = df.Date.min()
mx = df.Date.max()
dr = pd.date_range(mn - pd.tseries.offsets.MonthBegin(), mx + pd.tseries.offsets.MonthEnd(), name="Date")
df = df.set_index("Date").reindex(dr).reset_index()
df['Current_Price'] = df.groupby(
    pd.Grouper(key='Date', freq='1M'))['Current_Price'].ffill().bfill()

# The dataframe below shows the current price of the product
# I'd like to buy at the specific date_range
print(df)

# Create 'Day' column to know which day of the month
df['Day'] = pd.to_datetime(df['Date']).dt.day

# Create 'Deposit' column to record how much money is
# deposited in, say, my bank account to buy the product.
# 'Withdrawal' column is to record how much I spent in
# buying product(s) at the current price on a specific date.
# 'Num_of_Products_Bought' shows how many items I bought
# on that specific date.
#
# Please note that the calculate below takes into account
# the left over money, which remains after I've purchased a 
# product, for future purchase. For example, if you observe 
# the resulting dataframe at the end of this code, you'll 
# notice that I was able to purchase 7 products on March 1, 2021
# although my deposit on that day was $100. That is because 
# on the days leading up to March 1, 2021, I have been saving 
# the spare change from previous product purchases and that 
# extra money allows me to buy an extra product on March 1, 2021 
# despite my budget of $100 should only allow me to purchase 
# 6 products.
df[['Deposit', 'Withdrawal', 'Num_of_Products_Bought']] = 0.0

# Suppose I save $100 at the beginning of every month in my bank account
df.loc[df['Day'] == 1, 'Deposit'] = 100.0

for index, row in df.iterrows():
    if df.loc[index, 'Day'] == 1:
        # num_prod_bought = (sum_of_deposit_so_far - sum_of_withdrawal)/current_price
        df.loc[index, 'Num_of_Products_Bought'] = math.floor(
            (sum(df.iloc[0:(index + 1)]['Deposit'])
             - sum(df.iloc[0:(index + 1)]['Withdrawal']))
            / df.loc[index, 'Current_Price'])
        # Record how much I spent buying the product on specific date
        df.loc[index, 'Withdrawal'] = df.loc[index, 'Num_of_Products_Bought'] * df.loc[index, 'Current_Price']

print(df)
# This code above is working as intended,
# but how can I make it more efficient/pandas-like?
# In particular, I don't like to idea of having to
# iterate the rows and having to recalculate
# the running (sum of) deposit amount and
# the running (sum of) the withdrawal.

Как упоминалось в комментарии в коде, я хотел бы знать, как сделать то же самое, не перебирая строки одну за другой и вычисляя сумму строк до текущей строки в моей итерации (я читал StackOverflow и видел cumsum(), но я не думаю, что cumsum имеет понятие текущей строки в итерации).

Заранее большое спасибо за ваши предложения / ответы!

3
user1330974 20 Май 2021 в 19:17

1 ответ

Лучший ответ

Решение с использованием .apply:

def fn():
    leftover = 0
    amount, deposit = yield
    while True:
        new_amount, new_deposit = yield (deposit + leftover) // amount
        leftover = (deposit + leftover) % amount
        amount, deposit = new_amount, new_deposit


df = df.set_index("Date")
s = fn()
next(s)
m = df.index.day == 1
df.loc[m, "Deposit"] = 100
df.loc[m, "Num_of_Products_Bought"] = df.loc[
    m, ["Current_Price", "Deposit"]
].apply(lambda x: s.send((x["Current_Price"], x["Deposit"])), axis=1)
df.loc[m, "Withdrawal"] = (
    df.loc[m, "Num_of_Products_Bought"] * df.loc[m, "Current_Price"]
)
print(df.fillna(0).reset_index())

Печать:

          Date  Current_Price  Deposit  Num_of_Products_Bought  Withdrawal
0   2021-01-01            5.5    100.0                    18.0        99.0
1   2021-01-02            5.5      0.0                     0.0         0.0
2   2021-01-03            5.5      0.0                     0.0         0.0
3   2021-01-04            5.5      0.0                     0.0         0.0
4   2021-01-05            5.5      0.0                     0.0         0.0
5   2021-01-06            5.5      0.0                     0.0         0.0
6   2021-01-07            5.5      0.0                     0.0         0.0
7   2021-01-08            5.5      0.0                     0.0         0.0
8   2021-01-09            5.5      0.0                     0.0         0.0
9   2021-01-10            5.5      0.0                     0.0         0.0
10  2021-01-11            5.5      0.0                     0.0         0.0
11  2021-01-12            5.5      0.0                     0.0         0.0
12  2021-01-13            5.5      0.0                     0.0         0.0
13  2021-01-14            5.5      0.0                     0.0         0.0
14  2021-01-15            5.5      0.0                     0.0         0.0
15  2021-01-16            5.5      0.0                     0.0         0.0
16  2021-01-17            5.5      0.0                     0.0         0.0
17  2021-01-18            5.5      0.0                     0.0         0.0
18  2021-01-19            5.5      0.0                     0.0         0.0
19  2021-01-20            5.5      0.0                     0.0         0.0
20  2021-01-21            5.5      0.0                     0.0         0.0
21  2021-01-22            5.5      0.0                     0.0         0.0
22  2021-01-23            5.5      0.0                     0.0         0.0
23  2021-01-24            5.5      0.0                     0.0         0.0
24  2021-01-25            5.5      0.0                     0.0         0.0
25  2021-01-26            5.5      0.0                     0.0         0.0
26  2021-01-27            5.5      0.0                     0.0         0.0
27  2021-01-28            5.5      0.0                     0.0         0.0
28  2021-01-29            5.5      0.0                     0.0         0.0
29  2021-01-30            5.5      0.0                     0.0         0.0
30  2021-01-31            5.5      0.0                     0.0         0.0
31  2021-02-01           10.5    100.0                     9.0        94.5
32  2021-02-02           10.5      0.0                     0.0         0.0
33  2021-02-03           10.5      0.0                     0.0         0.0
34  2021-02-04           10.5      0.0                     0.0         0.0
35  2021-02-05           10.5      0.0                     0.0         0.0
36  2021-02-06           10.5      0.0                     0.0         0.0
37  2021-02-07           10.5      0.0                     0.0         0.0
38  2021-02-08           10.5      0.0                     0.0         0.0
39  2021-02-09           10.5      0.0                     0.0         0.0
40  2021-02-10           10.5      0.0                     0.0         0.0
41  2021-02-11           10.5      0.0                     0.0         0.0
42  2021-02-12           10.5      0.0                     0.0         0.0
43  2021-02-13           10.5      0.0                     0.0         0.0
44  2021-02-14           10.5      0.0                     0.0         0.0
45  2021-02-15           10.5      0.0                     0.0         0.0
46  2021-02-16           10.5      0.0                     0.0         0.0
47  2021-02-17           10.5      0.0                     0.0         0.0
48  2021-02-18           10.5      0.0                     0.0         0.0
49  2021-02-19           10.5      0.0                     0.0         0.0
50  2021-02-20           10.5      0.0                     0.0         0.0
51  2021-02-21           10.5      0.0                     0.0         0.0
52  2021-02-22           10.5      0.0                     0.0         0.0
53  2021-02-23           10.5      0.0                     0.0         0.0
54  2021-02-24           10.5      0.0                     0.0         0.0
55  2021-02-25           10.5      0.0                     0.0         0.0
56  2021-02-26           10.5      0.0                     0.0         0.0
57  2021-02-27           10.5      0.0                     0.0         0.0
58  2021-02-28           10.5      0.0                     0.0         0.0
59  2021-03-01           15.0    100.0                     7.0       105.0
60  2021-03-02           15.0      0.0                     0.0         0.0
61  2021-03-03           15.0      0.0                     0.0         0.0
62  2021-03-04           15.0      0.0                     0.0         0.0
63  2021-03-05           15.0      0.0                     0.0         0.0
64  2021-03-06           15.0      0.0                     0.0         0.0
65  2021-03-07           15.0      0.0                     0.0         0.0
66  2021-03-08           15.0      0.0                     0.0         0.0
67  2021-03-09           15.0      0.0                     0.0         0.0
68  2021-03-10           15.0      0.0                     0.0         0.0
69  2021-03-11           15.0      0.0                     0.0         0.0
70  2021-03-12           15.0      0.0                     0.0         0.0
71  2021-03-13           15.0      0.0                     0.0         0.0
72  2021-03-14           15.0      0.0                     0.0         0.0
73  2021-03-15           15.0      0.0                     0.0         0.0
74  2021-03-16           15.0      0.0                     0.0         0.0
75  2021-03-17           15.0      0.0                     0.0         0.0
76  2021-03-18           15.0      0.0                     0.0         0.0
77  2021-03-19           15.0      0.0                     0.0         0.0
78  2021-03-20           15.0      0.0                     0.0         0.0
79  2021-03-21           15.0      0.0                     0.0         0.0
80  2021-03-22           15.0      0.0                     0.0         0.0
81  2021-03-23           15.0      0.0                     0.0         0.0
82  2021-03-24           15.0      0.0                     0.0         0.0
83  2021-03-25           15.0      0.0                     0.0         0.0
84  2021-03-26           15.0      0.0                     0.0         0.0
85  2021-03-27           15.0      0.0                     0.0         0.0
86  2021-03-28           15.0      0.0                     0.0         0.0
87  2021-03-29           15.0      0.0                     0.0         0.0
88  2021-03-30           15.0      0.0                     0.0         0.0
89  2021-03-31           15.0      0.0                     0.0         0.0
90  2021-04-01           20.0    100.0                     5.0       100.0
91  2021-04-02           20.0      0.0                     0.0         0.0
92  2021-04-03           20.0      0.0                     0.0         0.0
93  2021-04-04           20.0      0.0                     0.0         0.0
94  2021-04-05           20.0      0.0                     0.0         0.0
95  2021-04-06           20.0      0.0                     0.0         0.0
96  2021-04-07           20.0      0.0                     0.0         0.0
97  2021-04-08           20.0      0.0                     0.0         0.0
98  2021-04-09           20.0      0.0                     0.0         0.0
99  2021-04-10           20.0      0.0                     0.0         0.0
100 2021-04-11           20.0      0.0                     0.0         0.0
101 2021-04-12           20.0      0.0                     0.0         0.0
102 2021-04-13           20.0      0.0                     0.0         0.0
103 2021-04-14           20.0      0.0                     0.0         0.0
104 2021-04-15           20.0      0.0                     0.0         0.0
105 2021-04-16           20.0      0.0                     0.0         0.0
106 2021-04-17           20.0      0.0                     0.0         0.0
107 2021-04-18           20.0      0.0                     0.0         0.0
108 2021-04-19           20.0      0.0                     0.0         0.0
109 2021-04-20           20.0      0.0                     0.0         0.0
110 2021-04-21           20.0      0.0                     0.0         0.0
111 2021-04-22           20.0      0.0                     0.0         0.0
112 2021-04-23           20.0      0.0                     0.0         0.0
113 2021-04-24           20.0      0.0                     0.0         0.0
114 2021-04-25           20.0      0.0                     0.0         0.0
115 2021-04-26           20.0      0.0                     0.0         0.0
116 2021-04-27           20.0      0.0                     0.0         0.0
117 2021-04-28           20.0      0.0                     0.0         0.0
118 2021-04-29           20.0      0.0                     0.0         0.0
119 2021-04-30           20.0      0.0                     0.0         0.0
1
Andrej Kesely 20 Май 2021 в 18:47