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I have a pandas dataframe and only want to sort the first three columns in my dataframe in a specific order. The order of the rest of the columns does not matter. I have 40 columns in total.

This thread had a solution but it doesn't seem to work for me: how to sort only some of the columns in a data frame in pandas?

The solution in the link above recommends tackling this problem in three steps by using reindex in the following way:

preordered = list('xyz')
new_order = preordered + list(df.columns - preordered)
df.reindex(columns=new_order)

In my case, the name of the three columns I want as first, second and third column are the following: in_Code, in_Name, and Code - in that specific order.

Since list() can only take on one argument, I used preordered=list(['in_Code','in_Name','Code']) for the first step.

Yet the second step, new_order=preordered + list(df.columns - preordered) gives me a TypeError: cannot perform __sub__ with this index type: Index.

Any help?

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2 Answers 2

Reset to default
2

IIUC,

df = pd.DataFrame(np.random.randint(0,100,(10,6)), columns=[*'ABWXYZ'])

orderedCols = ['Z','Y','W']
nonOrderedCols = [i for i in df.columns if i not in orderedCols]

nonOrderedCols
# ['A', 'B', 'X']

orderedCols
# ['Z', 'Y', 'W']

df.reindex(orderedCols + nonOrderedCols, axis=1)

Output:

    Z   Y   W   A   B   X
0  29  61  65  17  95  59
1  87   2  98   4  79  85
2  53  45   2  77  49  81
3  72  47  58  53  22  24
4  74  66  50  93  29  71
5  23  94  70  38  11  94
6  54  60   7  29   3  33
7  31   1  67  80  68  57
8  99  50  79  28  49  52
9  73  46  77  17  47  93

Note: You can also use nonOrderedCols = df.columns[~df.columns.isin(orderedCols)]

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1 Comment

This looks promising but the 'or' in your post is confusing.
2

If I understand your question correctly, you would use

 df.sort_values(by=['in_Code','in_Name','Code'])
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1 Comment

This didn't work for me. I get an error 'Check for Duplicates'. Is this sorting the values in the three columns, rather than the columns themselves? I would like the columns sorted, don't really care about the values.

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