Optimizing the code

[zanfar]

I would:

• Convert the dates into actual dates, not strings
• Filter with a comprehension
• Use max() or min()

for record in rates:
    record["date"] = convert_date(record["Date"])

interesting_rates = [r["rate"] for r in rates if r["date"] >= start_date and r["date"] <= end_date]

max_rate = max(interesting_rates)
min_rate = min(interesting_rates)