chatGPT prompt 2

answer.py

import csv
from datetime import datetime

# Open the input CSV file
with open('input.csv', 'r') as input_file:
    # Create a csv reader object
    reader = csv.reader(input_file)

    # Skip the header row
    next(reader)

    # Initialize a dictionary to store the data by date
    data = {}

    # Iterate over the rows in the input file
    for row in reader:
        # Extract the timestamp and convert it to a datetime object
        timestamp = datetime.strptime(row[0], '%Y-%m-%d %H:%M:%S')

        # Calculate the milliseconds since midnight
        milliseconds = int((timestamp - timestamp.replace(hour=0, minute=0, second=0, microsecond=0)).total_seconds() * 1000)

        # Extract the date from the timestamp
        date = timestamp.date()

        # If the date is not already in the dictionary, initialize a list for that date
        if date not in data:
            data[date] = []

        # Append the row data to the list for that date
        data[date].append([milliseconds] + row[1:])

    # Iterate over the data by date
    for date, rows in data.items():
        # Open a new CSV file with the date as the file name
        with open(f"{date}.csv", 'w') as output_file:
            # Create a csv writer object
            writer = csv.writer(output_file)

            # Write the rows to the output file
            writer.writerows(rows)

input.txt

could you rewrite that without using pandas, just use the standard CSV library