Timer

The code in this notebook helps with measuring time.

Prerequisites

• This notebook needs some understanding on advanced concepts in Python, notably
  • classes
  • the Python with statement
  • measuring time

Synopsis

To use the code provided in this chapter, write

>>> from debuggingbook.Timer import <identifier>

and then make use of the following features.

The Timer class allows you to measure elapsed real time (in fractional seconds). Its typical usage is in conjunction with a with clause:

>>> with Timer() as t:
>>>     some_long_running_function()
>>> t.elapsed_time()
0.025446416984777898

Measuring Time

The class Timer allows measuring the elapsed time during some code execution.

# ignore
from typing import Type, Any

def clock() -> float:
    """
    Return the number of fractional seconds elapsed since some point of reference.
    """
    return time.perf_counter()

class Timer:
    def __init__(self) -> None:
        """Constructor"""
        self.start_time = clock()
        self.end_time = None

    def __enter__(self) -> Any:
        """Begin of `with` block"""
        self.start_time = clock()
        self.end_time = None
        return self

    def __exit__(self, exc_type: Type, exc_value: BaseException,
                 tb: TracebackType) -> None:
        """End of `with` block"""
        self.end_time = clock()  # type: ignore

    def elapsed_time(self) -> float:
        """Return elapsed time in seconds"""
        if self.end_time is None:
            # still running
            return clock() - self.start_time
        else:
            return self.end_time - self.start_time  # type: ignore

Here's an example:

def some_long_running_function() -> None:
    i = 1000000
    while i > 0:
        i -= 1

print("Stopping total time:")
with Timer() as t:
    some_long_running_function()
print(t.elapsed_time())

Stopping total time:
0.024596250033937395

print("Stopping time in between:")
with Timer() as t:
    for i in range(10):
        some_long_running_function()
        print(t.elapsed_time())

Stopping time in between:
0.02577041694894433
0.050405749992933124
0.0758031249861233
0.10154120897641405
0.12715233396738768
0.1522330419975333
0.17718604195397347
0.20261654199566692
0.22783324995543808
0.25300645898096263

That's it, folks – enjoy!

Synopsis

The Timer class allows you to measure elapsed real time (in fractional seconds). Its typical usage is in conjunction with a with clause:

with Timer() as t:
    some_long_running_function()
t.elapsed_time()

0.025446416984777898

Lessons Learned

• With the Timer class, it is very easy to measure elapsed time.