python - Write comments in CSV file with pandas

Question

I would like to write some comments in my CSV file created with pandas. I haven't found any option for this in DataFrame.to_csv (even though read_csv can skip comments) neither in the standard csv module. I can open the file, write the comments (line starting with #) and then pass it to to_csv. Does any body have a better option?

Answer 1

df.to_csv accepts a file object. So you can open a file in a mode, write you comments and pass it to the dataframe to_csv function.

For example:

In [36]: df = pd.DataFrame({'a':[1,2,3], 'b':[1,2,3]})

In [37]: f = open('foo', 'a')

In [38]: f.write('# My awesome comment
')

In [39]: f.write('# Here is another one
')

In [40]: df.to_csv(f)

In [41]: f.close()

In [42]: more foo
# My awesome comment
# Here is another one
,a,b
0,1,1
1,2,2
2,3,3