Writing text file in Python produces empty file

Question

I'm working on a project where I have to keep track of model performance across different version releases. I'm trying to create and write a text file that contains some lines of text that signal turbulences in the model performance. This is the function I wrote (it contains some auxiliary functions but these are not relevant for my question):

def alarm(cell_line, conc, full_model_id, metric, treshold):
    v_model_results = get_model_across_versions(cell_line, conc, full_model_id)
    v_model_results2 = v_model_results.reset_index()[metric]
    percentages_list = calculate_percentages(v_model_results2)
    length = len(percentages_list)
    res = []
    with open('results.txt', 'w') as f:
        for i in range(length): if (percentages_list[i] < -treshold):
                f.write("The percentage treshold between the versions v" + str(i+13) + " and v" + str(i+14)+ " is exceeded for the metric " + metric +". There is a drop of " + str(-percentages_list[i]) + " percent." + "\n")
                print("The percentage treshold between the versions v" + str(i+13) + " and v" + str(i+14)+ " is exceeded for the metric " + metric +". There is a drop of " + str(-percentages_list[i]) + " percent.")
            else:
                print("No significant turbulence in performance between the versions v" + str(i+13) + " and v" + str(i+14)+ " for the metric " + metric + ".")
        f.close()

When I apply the above function to an example all the messages are printed correctly and it indeed generates a text file results.txt , but this file is empty. What am I doing wrong here?

Answer 1

open('results.txt', 'w') will open the file and overwrite any data in it. This could be causing your problem.

Try open('results.txt', 'a') . To append new text instead of overwritting.

Also, you don't need to include f.close() . The with statement handles that all for you.