Elapsed time context manager with checkpoints

gistfile1.py

from __future__ import print_function
import time
import contextlib

def format_checkpoints(cps):
    pairs = [cps[i:i+2] for i in range(len(cps)-1)]
    fmts = ["{0[0]} to {1[0]} in {2:.04f}s".format(start, end, end[1] - start[1])
            for start, end in pairs]
    return ", ".join(fmts)

@contextlib.contextmanager
def elapsed(name, logger=print):
    checkpoints = []
    def _checkpoint(cp):
        checkpoints.append((str(cp), time.time()))

    _checkpoint("start")
    yield _checkpoint
    _checkpoint("end")

    elapsed = checkpoints[-1][1] - checkpoints[0][1]
    logger(format_checkpoints(checkpoints))
    logger("Total elapsed time {:.04f}s".format(elapsed))

# Example:
# with elapsed("foobar") as cp:
#     time.sleep(1)
#     cp("foobaz")
#     time.sleep(1)
#     cp("foobar")
#     time.sleep(1)
#
# Output:
# start to foobaz in 1.0012s, foobaz to foobar in 1.0010s, foobar to end in 1.0012s
# Total elapsed time 3.0034s
#
# with elapsed("other thing", logging.info) as cp:
#     time.sleep(1)