处理ValueError的简便方法:无法从重复的轴重新索引 [英] Convenient way to deal with ValueError: cannot reindex from a duplicate axis

问题描述

我能够搜索显示此错误消息原因"的建议，但无法解决该问题-

I am able to search suggestions that show the 'cause' of this error message, but not how to address it -

每次我尝试通过在2个现有列中串联字符串值来向pandas数据帧添加新列时遇到此问题.

I encounter this problem every time I try to add a new column to a pandas dataframe by concatenating string values in 2 existing columns.

例如:

wind['timestamp'] = wind['DATE (MM/DD/YYYY)'] + ' ' + temp['stamp']

如果第一个项目和第二个项目与''合并为单独的数据帧/系列，则可以使用

It works if the first item and the second merged with ' ' are each separate dataframe/series.

这些尝试是为了使日期&时间合并到同一列中，以便熊猫图书馆将它们识别为日期时间戳.

These attempts are to have date & time merged into the same column so that they get recognized as datetime stamps by pandas library.

我不确定我是错误使用命令还是熊猫库功能在内部受到限制，因为它会不断返回 duplicate axis 错误msg.我知道后者极不可能哈哈哈...

I am not certain if I am wrongly using the command or if it is the pandas library features are internally limited, as it keeps returning the duplicate axis error msg. I understand the latter is highly unlikely hahaha ...

我能听到一些快速简便的解决方案吗?

Could I hear some quick and easy solution out of this?

我的意思是，我认为数据帧中列值之间的加/减以及所有这些运算将非常容易.在表上也可以看到它应该不难吗?

I mean, I thought sum/subtract and all these operations between column values in a dataframe would be quite easy. Shouldn't be too hard to have it visible on the table either right?

推荐答案

系列之间的操作需要无重复的索引，否则Pandas不知道如何在计算中对齐值.当前您的数据不是这种情况.

Operations between series require non-duplicated indices, otherwise Pandas doesn't know how to align values in calculations. This isn't the case with your data currently.

如果确定序列按位置对齐 ，则可以在每个数据帧上调用 reset_index :

If you are certain that your series are aligned by position, you can call reset_index on each dataframe:

wind = pd.DataFrame({'DATE (MM/DD/YYYY)': ['2018-01-01', '2018-02-01', '2018-03-01']})
temp = pd.DataFrame({'stamp': ['1', '2', '3']}, index=[0, 1, 1])

# ATTEMPT 1: FAIL
wind['timestamp'] = wind['DATE (MM/DD/YYYY)'] + ' ' + temp['stamp']
# ValueError: cannot reindex from a duplicate axis

# ATTEMPT 2: SUCCESS
wind = wind.reset_index(drop=True)
temp = temp.reset_index(drop=True)
wind['timestamp'] = wind['DATE (MM/DD/YYYY)'] + ' ' + temp['stamp']

print(wind)

  DATE (MM/DD/YYYY)     timestamp
0        2018-01-01  2018-01-01 1
1        2018-02-01  2018-02-01 2
2        2018-03-01  2018-03-01 3

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