[Solved] Python script for reformatting a text file into a csv using Python

Question

This could be done easily using a regular expression but I am guessing you do not wish to use that.

Instead the problem can be solved by reading the file in a line at a time and deciding if the line starts with a number followed by a .. If it does, start you start building up a list of lines until you find the next number.

Using Python’s int() function will attempt to convert a string into a number. The find('.') function attempts to locate the end of the number.

If the returned string is not a number, it causes a ValueError exception to be raised. In this case, add the line to the list of lines.

If there was a number, first write any existing entry to the csv file, and then start a new entry.

At the end, there will not be a final number line to trigger the next write, so add another call to write the final row to the csv.

For example:

import csv        

with open('text.txt') as f_input, open('output.csv', 'wb') as f_output:
    csv_output = csv.writer(f_output)
    entry = []

    for line in f_input:
        line = line.strip()    # Remove the trailing newline

        if len(line):          # Does the line containing anything?
            try:
                number = int(line[:line.find('.')])

                if len(entry):
                    csv_output.writerow(entry)
                entry = [number]
            except ValueError:
                entry.append(line)

    csv_output.writerow(entry)

Python’s csv library is used to take a list and automatically add the necessary commas between entries when writing to the csv output file. If an entry contains a comma, it will automatically add quotes.

Accepted Answer