TypeError: list indices must be integers or slices, not str

Question

I've got two lists that I want to merge into a single array and finally put it in a csv file. I'm a newbie with Python arrays and I don't understand how I can avoid this error :

def fill_csv(self, array_urls, array_dates, csv_file_path):
    result_array = []
    array_length = str(len(array_dates))

    # We fill the CSV file
    file = open(csv_file_path, "w")
    csv_file = csv.writer(file, delimiter=';', lineterminator='\n')

    # We merge the two arrays in one

    for i in array_length:
        result_array[i][0].append(array_urls[i])
        result_array[i][1].append(array_dates[i])
        i += 1

    csv_file.writerows(result_array)

And got :

  File "C:\Users\--\gcscan.py", line 63, in fill_csv
    result_array[i][0].append(array_urls[i])
TypeError: list indices must be integers or slices, not str

How can my count work ?

Answer 1

First, array_length should be an integer and not a string:

array_length = len(array_dates)

Second, your for loop should be constructed using range:

for i in range(array_length):  # Use `xrange` for python 2.

Third, i will increment automatically, so delete the following line:

i += 1

---

Note, one could also just zip the two lists given that they have the same length:

import csv

dates = ['2020-01-01', '2020-01-02', '2020-01-03']
urls = ['www.abc.com', 'www.cnn.com', 'www.nbc.com']

csv_file_patch = '/path/to/filename.csv'

with open(csv_file_patch, 'w') as fout:
    csv_file = csv.writer(fout, delimiter=';', lineterminator='\n')
    result_array = zip(dates, urls)
    csv_file.writerows(result_array)