Add the ability to compare a timer to another value.

[janfreyberg]

This allows checking whether the last measured time is greater
or less than some 'reference' value.

• Timer class now has a reference to the last-measured value; initially this is nan
• comparison operators are defined for Timer objects.

This is useful if you want to display messages if some operation
has taken too long in the past.

For example:

from codetiming import Timer
import time

image_display_timer = Timer()

def _display_hold_message():
    print('loading image...')

@image_display_timer
def display_image():
    if image_display_timer > 0.2:
        _display_hold_message()
    time.sleep(0.5)
    print('here is your image')

This results in a message being displayed when the function is used for the
second time:

>>> display_image()
here is your image
Elapsed time: 0.5051 seconds

>>> display_image()
loading image...
here is your image
Elapsed time: 0.5052 seconds

[janfreyberg]

I should note that I already use a pattern like this in a GUI application I have;
so I was happy to see this project!

[gahjelle]

@janfreyberg Thanks for the PR. This is an interesting use case.

A couple of suggestions:

• The ._value can potentially be interesting in itself, so we can promote it to be a variable without an underscore
• ._value is not really descriptive. How about something like .elapsed_time, .last_elapsed_time, or simply .last instead?
• Timer is a dataclass, so we don't need to manually implement comparison operators. We can rather add (order=True) to the decorator and make sure ._value is the first instance variable. See https://realpython.com/python-data-classes/#comparing-cards for an example.

Thanks for the idea.

[gahjelle]

Hmm ... reusing the dataclass comparison operators may not immediately give us comparisons to numbers. I'll do some more investigations.

[janfreyberg]

Sounds good!

elapsed_time sounds good, but I think then it may also be worth re-setting it to nan when calling start again, to avoid confusion. What do you think? If it's called last_elapsed_time, that doesn't seem so important.

I didn't know about this dataclass feature. I initially tried to save some code by using the functools.total_ordering decorator on the class, but it doesn't actually work when the value is nan, as it assumes that if a > b is false and a == b is false then a < b has to be true, which is not the case for nan (all will be false).

[gahjelle]

Hi, I had a look at how the comparison operators are implemented in data classes, and I don't think my suggestion will work, because they will only compare to other Timer objects, which is not what we want.

In the spirit of keeping this as simple as possible, I suggest the following:

• Expose an attribute called .last which is initialized to math.nan and hidden from init and repr.

• Update .last to be equal to the current elapsed_time when a timer ends. I don't think we can reset it to math.nan when a timer starts, because then your example above would not work 😊

• While it's a minor time penalty, I might suggest just do a search and replace elapsed_time with self.last inside stop(). Keeps the code very simple.

• Then we don't implement any comparison at all. Instead, the users can use the .last attribute explicitly. In your example, the relevant lines would then be:

  if image_display_timer.last > 0.2:
      _display_hold_message()
  

  This is both easier to implement and more explicit about what's happening

What do you think?

[janfreyberg]

Sounds like a good plan to me; all very good points :)

I'll do that now.

[gahjelle]

This looks great! I have two tiny comments on the test file. Otherwise, this should be ready to go.

I'll add a changelog (#15 ) and a list of contributors (#14 ) to the repo as well (hopefully tomorrow) so that you'll get proper credit. Thanks for your efforts!

[gahjelle]

Brilliant, thank you so much!

I'll add the changelog and list of contributors later today, and then make a new release on PyPI.

[janfreyberg]

Awesome, thank you 😃 will update my GUI projects as soon as the new release is out.

[gahjelle]

codetiming v1.1.0 has been released 🚀 🎉