GeezerVison

import os
import shelve
import tempfile
import timeit

def clearshelf(db):
    keys = list(db.keys())
    for k in keys:
        del db[k]

def test_clear(use_clear_method):
    with tempfile.TemporaryDirectory() as tempdir:
        filename = os.path.join(tempdir, "test-shelf")
        with shelve.open(filename) as db:
            items = {str(x):x for x in range(10000)}
            db.update(items)
            if use_clear_method:
                db.clear()
            else:
                clearshelf(db)
            assert len(db) == 0

test_with_clear = lambda: test_clear(True)
test_without_clear = lambda: test_clear(False)

if __name__ == "__main__":
    TRIALS = 5
    method_time = timeit.timeit(test_with_clear, number=TRIALS, globals=globals()) / TRIALS
    print(f"method:\t{method_time:.3}")
    func_time = timeit.timeit(test_without_clear, number=TRIALS, globals=globals()) / TRIALS
    print(f"func:\t{func_time:.3}")

james@iris cpython-build % ./python.exe ~/shelve-clear-test.py 
method:	0.596
func:	0.0272

[james@trina cpython-build]$ ./python ~/shelve-clear-test.py 
method: 0.0775
func:   0.0305

method: 13.5
func:   13.4