pandas DataFrame output end of csv

Question

I wonder how to add new DataFrame data onto the end of an existing csv file? The to_csv doesn't mention such functionality.

Answer 1

You can append using to_csv by passing a file which is open in append mode:

with open(file_name, 'a') as f:     df.to_csv(f, header=False) 

Use header=None, so as not to append the column names.

In fact, pandas has a wrapper to do this in to_csv using the mode argument (see Joe's answer):

df.to_csv(f, mode='a', header=False) 

Answer 2

You can also pass the file mode as an argument to the to_csv method

df.to_csv(file_name, header=False, mode = 'a')