pandas 确定熊猫数据框中的列值何时发生变化
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Determining when a column value changes in pandas dataframe
提问by badrobit
I am looking to write a quick script that will run through a csv file with two columns and provide me the rows in which the values in column B switch from one value to another:
我希望编写一个快速脚本，该脚本将运行包含两列的 csv 文件，并为我提供 B 列中的值从一个值切换到另一个值的行：
eg:
例如：
dataframe:
数据框：
# | A | B
--+-----+-----
1 | 2 | 3
2 | 3 | 3
3 | 4 | 4
4 | 5 | 4
5 | 5 | 4
would tell me that the change happened between row 2 and row 3. I know how to get these values using for loops but I was hoping there was a more pythonic way of approaching this problem.
会告诉我变化发生在第 2 行和第 3 行之间。我知道如何使用 for 循环获取这些值，但我希望有一种更 Pythonic 的方法来解决这个问题。
回答by Kathirmani Sukumar
You can create a new column for the difference
您可以为差异创建一个新列
> df['C'] = df['B'].diff()
> print df
# A B C
0 1 2 3 NaN
1 2 3 3 0
2 3 4 4 1
3 4 5 4 0
4 5 5 4 0
> df_filtered = df[df['C'] != 0]
> print df_filtered
# A B C
2 3 4 4 1
This will your required rows
这将是您所需的行
