pandas 熊猫如何交换或重新排序列
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pandas how to swap or reorder columns
提问by Yun Tae Hwang
I know that there are ways to swap the column order in python pandas. Let say I have this example dataset:
我知道有一些方法可以在 python pandas 中交换列顺序。假设我有这个示例数据集：
import pandas as pd
employee = {'EmployeeID' : [0,1,2],
'FirstName' : ['a','b','c'],
'LastName' : ['a','b','c'],
'MiddleName' : ['a','b', None],
'Contact' : ['(M) 133-245-3123', '(F)[email protected]', '(F)312-533-2442 [email protected]']}
df = pd.DataFrame(employee)
The one basic way to do would be:
一种基本的方法是：
neworder = ['EmployeeID','FirstName','MiddleName','LastName','Contact']
df=df.reindex(columns=neworder)
However, as you can see, I only want to swap two columns. It was doable just because there are only 4 column, but what if I have like 100 columns? what would be an effective way to swap or reorder columns?
但是，如您所见，我只想交换两列。这是可行的，因为只有 4 列，但是如果我有 100 列呢？交换或重新排序列的有效方法是什么？
There might be 2 cases:
可能有2种情况：
- when you just want 2 columns swapped.
- when you want 3 columns reordered. (I am pretty sure that this case can be applied to more than 3 columns.)
- 当您只想交换 2 列时。
- 当您想要重新排序 3 列时。（我很确定这种情况可以应用于 3 列以上。）
Thank you guys.
谢谢你们。
回答by sanster9292
Say your current order of column is [b,c,d,a] and you want to order it into [a,b,c,d], you could do it this way:
假设您当前的列顺序是 [b,c,d,a] 并且您想将其排序为 [a,b,c,d]，您可以这样做：
new_df = old_df[['a', 'b', 'c', 'd']]
回答by Vivek Kalyanarangan
Two column Swapping
两列交换
cols = list(df.columns)
a, b = cols.index('LastName'), cols.index('MiddleName')
cols[b], cols[a] = cols[a], cols[b]
df = df[cols]
Reorder column Swapping (2 swaps)
重新排序列交换（2 次交换）
cols = list(df.columns)
a, b, c, d = cols.index('LastName'), cols.index('MiddleName'), cols.index('Contact'), cols.index('EmployeeID')
cols[a], cols[b], cols[c], cols[d] = cols[b], cols[a], cols[d], cols[c]
df = df[cols]
Swapping Multiple
交换多个
Now it comes down to how you can play with list slices -
现在归结为如何使用列表切片 -
cols = list(df.columns)
cols = cols[1::2] + cols[::2]
df = df[cols]
