Convert a music .cue file into a label file. This module will accept an optional string attribute that specifies the input .cue file. If this file is not provided in the call then file-select box will be presented to the user. Output is a .txt file of labels that can be input into Audacity.

cue2labels.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""Convert a music .cue file into a label file.

This module will accept an optional string attribute that specifies the input
.cue file. If this file is not provided in the call then file-select box will
be presented to the user. Output is a .txt file of labels that can be input
into Audacity.

Examples:
        $ python cue2labels.py
        $ python cue2labels.py "InputFile.cue"

"""

def stringtime_to_millisec(stringtime):
    """

    Parameters
    ----------
    stringtime : STRING
        A string in the form of "HH:MM:SS:MS", where MS are millisecs.
        Hours(HH) and Minutes(MM) are optional.
        Seconds(SS) and Millisecs(MS) are mandatory.
        Example: 10:05:12 = 10hrs, 5mins, 12ms

    Returns
    -------
    FLOAT
        Returns a the input stringtime as decimal seconds

    """
    hours, minutes, seconds, milliseconds = (["00", "00"] + stringtime.split(":"))[-4:]
    hours = int(hours[-2:])*360
    minutes = int(minutes[-2:])*60 
    seconds = int(seconds[-2:])
    milliseconds = float(milliseconds[-2:])/60
    return hours + minutes + seconds + milliseconds


def parse_cue(cue_filename):
    """
    
    Parameters
    ----------
    cue_filename : STRING
        The name of the .cue file to be read and parsed.

    Returns
    -------
    track_times : LIST
        The time that the audio track starts, as given in the .cue file, 
        in decimal seconds
    titles : LIST
        The title of the track, as given in the .cue file.

    """
    from re import findall
    
    file = open(cue_filename, 'r') 
    track_times = [float(0)]
    titles = []
    
    while True: 
        # Get next line from file 
        line = file.readline() 
      
        # if line is empty end of file is reached 
        if not line: 
            break
        if line.strip()[:5] == 'INDEX 01':
            stringtime = stringtime_to_millisec(line.strip())
            if stringtime != float(0):
                track_times.append(stringtime)
        elif line.strip()[:5] == 'TITLE':
            track = findall(r'"([^"]*)"', line)
            titles.append(track)                

    # I've had trouble in the past         
    if not titles or track_times[-1]==float(0):
         warning_string = '''There is someting wrong with the .cue file, it\'s not formatted properly.
         Unable to continue processing!'''
         sys.exit(warning_string)     
    file.close() 
    return track_times, titles

    
def write_labels(label_filename, track_times, titles):
    """

    Parameters
    ----------
    label_filename : STRING
        The desired path/name of the output label file.
    track_times : LIST        
        The time that the audio track starts, as given in the .cue file, 
        in decimal seconds
    titles : LIST
        The title of the track, as given in the .cue file.

    Returns
    -------
    bool

    """
    # Due to the format of the .cue file, the first track title may be the album title
    if len(titles) > len(track_times):
        titles.pop(0)
        
    file = open(label_filename, "w")
    # Write out in tab delimited format
    for i in range(len(titles)):
        line = f"{track_times[i]:.5f}\t{track_times[i]:.5f}\t{titles[i][0]}"
        file.write(line)
        file.write("\n")
    
    file.close()
    return True


if __name__ == "__main__":
    import sys
    import os
    
    # Check if .cue file was given in the python call
    try:
        cue_filename = str(sys.argv[1])
    # If not, ask user to select        
    except:
        from tkinter.filedialog import askopenfilename
        cue_filename = askopenfilename(title="Select a cue file", filetypes=(("cue files",'*.cue'),))
        ## EXIT if user selects cancel
    
    # Read cue file and parse out the times and titles
    track_times, titles = parse_cue(cue_filename)
    # Make a label file name
    label_filename = os.path.splitext(cue_filename)[0]+'_labels.txt'
    # Write times and tracks to label file in proper format
    write_labels(label_filename, track_times, titles)
    print("File created")

I can't find a way to comment in your blog article, so I will leave one here.

The "millisecond" part (last two digits) in an index is actually frame count, which each second has 75 (reference). So it should be

milliseconds = float(milliseconds[-2:])/75

(Also there is an obvious typo in docstring: Example: 10:05:12 = 10hrs, 5mins, 12ms.)