How to write to csv a dataframe with config line before headers

Question

I’m using a pyhton script to manage different logfiles from an acquisition system, boards ecc.
I’m building a big dataframe which is the merge of other dfs and at the end i’m putting it to a csv file, below last line:

dF_COMP.to_csv(path1 + nomefile, sep=';', decimal= ',' , columns=columns)

I want to add in the first line of the csv a row with configuration parameters.

I can build the csv with the dataframe, then open it again and then add the line but I think is not the best idea as I expect to build even big files…
Any better idea?

Asked By: Federico Zanetta

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Answer 1

I can build the csv with the dataframe, then open it again and then add the line but I think is not the best idea as I expect to build even big files…

Do the opposite:

with open(path1 + nomefile, 'w') as csvfile:
    csvfile.write(f'# Config blah blahn')  # note the '#' as comment character
    df.to_csv(csvfile, sep=';', decimal= ',', columns=columns)

To read the file again with pd.read_csv:

pd.read_csv(path1 + nomefile, comment='#')  # to skip lines begin with '#'

# OR

pd.read_csv(path1 + nomefile, skiprows=1)  # to skip the first line

Answered By: Corralien

How to write to csv a dataframe with config line before headers

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