A Python function to format a float seconds value into a string representation for milliseconds, microseconds, nanoseconds, or picoseconds

format_seconds.py

def format_seconds(seconds):
    """
    Format a decimal number of seconds into the most appropriate unit
    (ms, μs, ns, ps) with engineering notation exponents (3, 6, 9, 12),
    truncated to 2 decimal places.

    Args:
        seconds (float): Time in seconds

    Returns:
        str: Formatted time string with appropriate unit

    Examples:
        format_seconds(0.125) => "125.00 ms"
        format_seconds(0.0000035) => "3.50 μs"
        format_seconds(0.0000000078) => "7.80 ns"
    """

    abs_seconds = abs(seconds)

    if abs_seconds >= 1:
        # seconds (10^0)
        return f"{seconds:.2f} s"
    if abs_seconds >= 0.001:
        # milliseconds (10^-3)
        return f"{seconds * 1000:.2f} ms"
    elif abs_seconds >= 0.000001:
        # microseconds (10^-6)
        return f"{seconds * 1000000:.2f} μs"
    elif abs_seconds >= 0.000000001:
        # nanoseconds (10^-9)
        return f"{seconds * 1000000000:.2f} ns"
    else:
        # picoseconds (10^-12)
        return f"{seconds * 1000000000000:.2f} ps"

def main():
    # Test cases
    test_values = [
        (1.0, "1.00 s"),
        (0.1, "100.00 ms"),
        (0.001, "1.00 ms"),
        (0.0005, "500.00 μs"),
        (0.0001, "100.00 μs"),
        (0.000001, "1.00 μs"),
        (0.0000005, "500.00 ns"),
        (0.0000001, "100.00 ns"),
        (0.000000001, "1.00 ns"),
        (0.0000000005, "500.00 ps"),
        (0.0000000001, "100.00 ps"),
        (0.00000000001, "10.00 ps"),
        (-0.0001, "-100.00 μs"),  # Test negative numbers
    ]

    print("Testing format_seconds function:")
    print("-" * 40)

    pass_count = 0
    fail_count = 0

    for value, expected in test_values:
        result = format_seconds(value)
        if result == expected:
            status = "PASS"
            pass_count = pass_count + 1
        else:
            status = "FAIL"
            fail_count = fail_count + 1

        print(f"Input: {value:.12f} seconds")
        print(f"Result: {result}")
        print(f"Expected: {expected}")
        print(f"Status: {status}")
        print("-" * 40)

    print(f"PASSED = {pass_count}")
    print(f"FAILED = {fail_count}")

if __name__ == "__main__":
    main()