withstopwatch 0.3.0

Stopwatch as a context manager.

# >>> from withstopwatch import Stopwatch

Basic usage:
>>> with Stopwatch():
...     print('<some activity to be measured>')
<some activity to be measured>
0 ms

Fields:
>>> with Stopwatch() as s:
...     pass
0 ms
>>> assert isinstance(s.label, str) and s.label == '0 ms'
>>> assert isinstance(s.ms, int) and s.ms == 0
>>> assert isinstance(s.s, int) and s.s == 0
>>> assert isinstance(s.seconds, float) and s.seconds > 0
>>> assert isinstance(s.timedelta, datetime.timedelta)
>>> assert isinstance(s.start, datetime.datetime)
>>> assert isinstance(s.stop, datetime.datetime)
>>> assert s.stop - s.start == s.timedelta

`str` and `repr`:
>>> assert str(s) == s.label
>>> repr(s)  # doctest: +ELLIPSIS
'<Stopwatch: datetime.timedelta(...)>'

Silencing:
>>> with Stopwatch(template=None) as s:
...     pass
>>> assert s.label is None
>>> with Stopwatch(print=None) as s:
...     pass
>>> assert s.label == '0 ms'

Special print:
>>> with Stopwatch(print=lambda line: print('DEBUG:', line)) as s:
...     pass
DEBUG: 0 ms

Templates:
>>> with Stopwatch(template='passing'):
...     pass
0 ms: passing
>>> with Stopwatch('passing'):
...     pass
0 ms: passing
>>> with Stopwatch('{ms} ms'):
...     pass
0 ms
>>> with Stopwatch('{s} s'):
...     pass
0 s
>>> with Stopwatch('{:.03f} (i.e. {seconds:.03f})'):
...     pass
0.000 (i.e. 0.000)
>>> with Stopwatch('{timedelta}'):
...     pass   # doctest: +ELLIPSIS
0:00:00...
>>> with Stopwatch('from {start!r} to {stop!r}') as s:
...     pass   # doctest: +ELLIPSIS
from datetime.datetime(...) to datetime.datetime(...)

With an exception (note: due to limitations of `doctest`, we can't check
easily both that something is printed and that an exception is raised):
>>> with Stopwatch(print=None):
...     raise Exception()
Traceback (most recent call last):
Exception
>>> try:
...     with Stopwatch() as s:
...        raise Exception()
... except Exception as exc:
...     print(repr(s))  # doctest: +ELLIPSIS
0 ms (failed)
<Stopwatch: datetime.timedelta(...)>
>>> try:
...     with Stopwatch('abc') as s:
...        raise Exception()
... except Exception as exc:
...     print(repr(s))  # doctest: +ELLIPSIS
0 ms: abc (failed)
<Stopwatch: datetime.timedelta(...)>

Testing with `time.sleep` (note: the tests may fail during a slower run):
>>> import time
>>> with Stopwatch() as s:
...     time.sleep(0.1)
100 ms
>>> assert 0.1 < s.seconds < 0.2

Embedded stopwatches:
>>> with Stopwatch('outer'):
...     with Stopwatch('inner'):
...         pass
0 ms: inner
0 ms: outer

Measuring the overhead of Stopwatch using Stopwatch itself
(note: the tests may fail during a slower run):
>>> with Stopwatch(print=None) as s1:
...     with Stopwatch('inner') as s2:
...         pass
0 ms: inner
>>> with Stopwatch(print=None) as s3:
...     pass
>>> overhead = s1.seconds - s3.seconds
>>> assert 0 <= overhead < 0.0001
... # ~20 us on i5@2.60GHz, Python 3.6.0, Linux