在Python中,有一种方法可以逐渐修改我正在复制的行中的值吗?

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英文:

In Python, is there a way to progressively modify a value in a row that I am duplicating?

问题

使用https://stackoverflow.com/questions/32792263/duplicate-row-based-on-value-in-different-column作为框架。

由于我正在基于“数量”列的值复制行,是否有一种方法可以修改复制行的值?例如,对于第一行,当行被复制时,我想将“价格”的值从20更改为21,如果您要复制该行3次,我想要“价格”值为23,依此类推。

英文:

Using https://stackoverflow.com/questions/32792263/duplicate-row-based-on-value-in-different-column as a framework.

As I am duplicating the rows based on the value of the Quantity column, is there a way to then modify the value of the duplicated row? As an example, for the first row, when the row is duplicated I want to change the value of the Price from 20 to 21 and if you were to duplicate the row 3 times, I would want the Price value to be 23, so on and so forth.

答案1

得分: 1

使用您提到的问题中的设置:

d = {
    '1': ['20', 'NYC', '2'],
    '2': ['30', 'NYC', '2'],
    '3': ['5', 'NYC', '2'],
    '4': ['300', 'LA', '2'],
    '5': ['30', 'LA', '2'],
    '6': ['100', 'LA', '2']
}

columns = ['Price', 'City', 'Quantity']

# 创建数据框并重命名列
df = pd.DataFrame.from_dict(
    data=d, orient='index'
)
df.columns = columns

使用来自该问题的最受欢迎的答案来复制行:

df = df.loc[df.index.repeat(df.Quantity)]

您可以通过按索引分组并使用 cumcount 来增加价格,如下所示:

df['Price Increase'] = df.groupby(df.index).cumcount() + 1

df['New Price'] = df['Price Increase'] + df['Price'].astype(float)

给出结果:

  Price City Quantity  Price Increase  New Price
1    20  NYC        2               1       21.0
1    20  NYC        2               2       22.0
2    30  NYC        2               1       31.0
2    30  NYC        2               2       32.0
3     5  NYC        2               1        6.0
3     5  NYC        2               2        7.0
4   300   LA        2               1      301.0
4   300   LA        2               2      302.0
5    30   LA        2               1       31.0
5    30   LA        2               2       32.0
6   100   LA        2               1      101.0
6   100   LA        2               2      102.0
  • 我为了清晰起见保留了一些额外的列,但如果您希望如此,您可以将价格替换为 New Price 并删除额外的列。
英文:

Using the Setup from the question you referred to:


d = {
    '1': ['20',  'NYC', '2'],
    '2': ['30',  'NYC', '2'],
    '3': ['5',   'NYC', '2'],
    '4': ['300', 'LA',  '2'],
    '5': ['30',  'LA',  '2'],
    '6': ['100', 'LA',  '2']
}

columns=['Price', 'City', 'Quantity']

# create dataframe and rename columns

df = pd.DataFrame.from_dict(
    data=d, orient='index'
)
df.columns = columns

Using the most upvoted answer from that question to duplicate the rows:

df = df.loc[df.index.repeat(df.Quantity)]

You can increase the price by grouping by the index and using cumcount as follows:

df['Price Increase'] = df.groupby(df.index).cumcount() + 1

df['New Price'] = df['Price Increase'] + df['Price'].astype(float)

Giving the result:

  Price City Quantity  Price Increase  New Price
1    20  NYC        2               1       21.0
1    20  NYC        2               2       22.0
2    30  NYC        2               1       31.0
2    30  NYC        2               2       32.0
3     5  NYC        2               1        6.0
3     5  NYC        2               2        7.0
4   300   LA        2               1      301.0
4   300   LA        2               2      302.0
5    30   LA        2               1       31.0
5    30   LA        2               2       32.0
6   100   LA        2               1      101.0
6   100   LA        2               2      102.0


*I left some extra columns for clarity, but you could just replace price with the New Price and remove the additional columns, if that is what you want.

答案2

得分: 0

假设您有像我的虚拟DataFrame上的Product列那样的唯一键我会这样做

```python
import pandas as pd
import numpy as np

# 创建虚拟DataFrame
df = pd.DataFrame(np.random.randint(low=0, high=10, size=(4, 2)), columns=["Quantity", "Price"])
df["Product"] = np.arange(4)
df = df[["Product", "Quantity", "Price"]]
print("原始DataFrame".center(30, '-'))
print(df)

print()
# 创建重复的列
df = df.loc[df.index.repeat(df['Quantity'])]

# 在新的DataFrame上更改价格
df["Price"] = df.groupby("Product", group_keys=False)["Price"].apply(lambda x: x + np.arange(x.shape[0]))
df.index = np.arange(df.shape[0])
print("更改后的DataFrame".center(30, '-'))
print(df)

<details>
<summary>英文:</summary>

Assuming you have a unique key like the &quot;Product&quot; column on my dummy DataFrame I&#39;d do something like this:

```python
import pandas as pd
import numpy as np


# Dummy DataFrame creation
df = pd.DataFrame(np.random.randint(low=0, high=10, size=(4, 2)), columns=[&quot;Quantity&quot;, &quot;Price&quot;])
df[&quot;Product&quot;] = np.arange(4)
df = df[[&quot;Product&quot;, &quot;Quantity&quot;, &quot;Price&quot;]]
print(&quot;Original DataFrame&quot;.center(30, &#39;-&#39;))
print(df)

print()
# Creating repeated columns
df = df.loc[df.index.repeat(df[&#39;Quantity&#39;])]

# Changing price on new df
df[&quot;Price&quot;] = df.groupby(&quot;Product&quot;, group_keys=False)[&quot;Price&quot;].apply(lambda x: x + np.arange(x.shape[0]))
df.index = np.arange(df.shape[0])
print(&quot;Changed DataFrame&quot;.center(30, &#39;-&#39;))
print(df)

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  • 本文由 发表于 2023年7月17日 21:43:21
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