Python stopwatch context manager to measure the time of operations

stopwatch.py

import time
from contextlib import ContextDecorator

class Stopwatch(ContextDecorator):
    """
    Context manager to time the duration of operations.

    Example:
        >>> import time
        >>> with Stopwatch(timer='wall') as sw:
        ...        time.sleep(1)
        >>> print(f'Took {sw.elapsed:.0f}s')
        Took 1s
    """

    def __init__(self, timer='wall'):
        """
        The timer type can be any of:
         - wall (default): real-word clock time
         - cpu: CPU performance counter (e.g. taking into account clock speed variations)
         - process: Similar to cpu, but only counting our process (incl. system)
        """
        if timer == 'cpu':
            self.timer = time.perf_counter
        elif timer == 'wall':
            self.timer = time.time
        elif timer == 'process':
            self.timer = time.process_time
        else:
            raise ValueError(f'Timer type "{timer}" is invalid.')
        self.elapsed = 0

    def __enter__(self):
        self.time = self.timer()
        return self

    def __exit__(self, type, value, traceback):
        elapsed = self.timer() - self.time
        self.elapsed = elapsed