将列作为副本添加到 Pandas DataFrame
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Adding a column to a Pandas DataFrame as a copy
提问by Roger
I have a pandas DataFrame called originaland I would like to add a new column to it and save the resultant DataFrame in a variable called modified. How do I do that?
我有一个名为original 的Pandas DataFrame ，我想向其中添加一个新列，并将生成的 DataFrame 保存在名为modified的变量中。我怎么做？
import pandas as pd
import numpy as np
original = pd.DataFrame(np.random.randn(5, 2), columns=['a', 'b'])
The solution given in the very similarly named questions here is to do something like:
此处名称非常相似的问题中给出的解决方案是执行以下操作：
original['c'] = original['b'].abs()
This does not work for me because it modifies the originalDataFrame. A potential solution is to use join, but that does not allow me to name it nor does it allow it be filled with a scalar values:
这对我不起作用，因为它修改了原始DataFrame。一个潜在的解决方案是使用 join，但这不允许我命名它，也不允许它填充标量值：
modified = original.join(original['b'].abs(),rsuffix='_abs')
The aim is to able to add the column in a single line without temp variables to achieve the following effect:
目的是能够在没有临时变量的情况下将列添加到一行中，以实现以下效果：
modified = original.some_op() \
.a_different_op() \
.add_a_column() \ # <- the step I can't figure out
.another_op() \
.final_op()
回答by wirrbel
Use pandas.DataFrame.assignmethod it is described here http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.assign.html
pandas.DataFrame.assign这里描述的使用方法http://pandas.pydata.org/pandas-docs/stable/generated/pandas.DataFrame.assign.html
