Generate a Monthly Report CSV from Log Files in Python

import csv
from collections import defaultdict
from datetime import datetime

def generate_monthly_report(log_file: str, month: str, output_file: str) -> None:
    events_by_date = defaultdict(int)
    revenue_by_date = defaultdict(float)
    
    with open(log_file, 'r') as f:
        for line in f:
            date_str, _, revenue_str = line.strip().split(',')
            if date_str.startswith(month):
                events_by_date[date_str] += 1
                revenue_by_date[date_str] += float(revenue_str)
    
    with open(output_file, 'w', newline='') as f:
        writer = csv.writer(f)
        writer.writerow(['date', 'events', 'revenue'])
        for date in sorted(events_by_date):
            writer.writerow([date, events_by_date[date], round(revenue_by_date[date], 2)])

if __name__ == "__main__":
    sample_logs = "2024-03-01,login,10.50\n2024-03-01,purchase,25.00\n2024-03-02,purchase,12.75\n2024-04-01,login,5.00"
    with open("logs.txt", 'w') as f:
        f.write(sample_logs)
    
    generate_monthly_report("logs.txt", "2024-03", "march_report.csv")
    
    with open("march_report.csv") as f:
        print(f.read())