How to add header row to a pandas DataFrame

Question

I am reading a csv file into pandas. This csv file constists of four columns and some rows, but does not have a header row, which I want to add. I have been trying the following:

Cov = pd.read_csv("path/to/file.txt", sep='\t')
Frame=pd.DataFrame([Cov], columns = ["Sequence", "Start", "End", "Coverage"])
Frame.to_csv("path/to/file.txt", sep='\t')

But when I apply the code, I get the following Error:

ValueError: Shape of passed values is (1, 1), indices imply (4, 1)

What exactly does the error mean? And what would be a clean way in python to add a header row to my csv file/pandas df?

Here is a different interpretation of your question: Add another header to an existing Dataframe to create a MultiIndex. — cs95, May 24 '19 at 06:44

score 324 · Accepted Answer · edited May 24 '19 at 06:42

324

You can use names directly in the read_csv

names : array-like, default None List of column names to use. If file contains no header row, then you should explicitly pass header=None

Cov = pd.read_csv("path/to/file.txt", 
                  sep='\t', 
                  names=["Sequence", "Start", "End", "Coverage"])

edited May 24 '19 at 06:42

cs95

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answered Dec 04 '15 at 15:43

Leb

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11

You will laugh. I actually tried this, but was unaware of that you have to put the square brackets around the names. Which is logically in retrospect. Thank you! – sequence_hard Dec 04 '15 at 15:49
1

No worries, we've all done those silly mistakes. I'm guilty of them too. – Leb Dec 04 '15 at 15:50
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@Leb, I had exactly the same problem and I tried your solution. I got the headers for the table but the first row was also replaced by the same header names. What shold I do now? – 007mrviper Nov 13 '18 at 18:28
it adds more collumns to my data, all with `NaN` attributes. It was because my separator is a empty space. – SalahAdDin Jan 23 '20 at 13:32
Is there a reason why if you create a DataFrame the attribute is called one thing and you a csv file it is called something else. There are like 3 different names I believe for this header label attribute depending upon which function you are using. – demongolem Aug 31 '20 at 11:49

Anton Protopopov · Answer 2 · 2016-03-25T21:55:48.587

156

Alternatively you could read you csv with header=None and then add it with df.columns:

Cov = pd.read_csv("path/to/file.txt", sep='\t', header=None)
Cov.columns = ["Sequence", "Start", "End", "Coverage"]

edited Mar 25 '16 at 21:55

answered Dec 04 '15 at 17:27

Anton Protopopov

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This was very helpful and an easy way. Thanks @AntonProtopopov – Priya May 26 '21 at 07:16

score 19 · Answer 3 · edited Feb 05 '18 at 05:37

19

col_Names=["Sequence", "Start", "End", "Coverage"]
my_CSV_File= pd.read_csv("yourCSVFile.csv",names=col_Names)

having done this, just check it with[well obviously I know, u know that. But still...

my_CSV_File.head()

Hope it helps ... Cheers

edited Feb 05 '18 at 05:37

Amarth Gûl

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answered Jan 24 '18 at 03:08

Bhardwaj Joshi

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Please format your code with the `{}` button. Indentation matters. – Mr. T Jan 24 '18 at 03:38

score 11 · Answer 4 · answered Feb 05 '18 at 06:35

11

To fix your code you can simply change [Cov] to Cov.values, the first parameter of pd.DataFrame will become a multi-dimensional numpy array:

Cov = pd.read_csv("path/to/file.txt", sep='\t')
Frame=pd.DataFrame(Cov.values, columns = ["Sequence", "Start", "End", "Coverage"])
Frame.to_csv("path/to/file.txt", sep='\t')

But the smartest solution still is use pd.read_excel with header=None and names=columns_list.

answered Feb 05 '18 at 06:35

romulomadu

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When we give columns_list, can we add default values for selected columns? – YoungSheldon Jan 06 '20 at 18:14

How to add header row to a pandas DataFrame

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