Profile a code block

profile.py

import cProfile
import contextlib
import io
import pstats


@contextlib.contextmanager
def profile(max_results=-1, pattern="*"):
    """
    Profile a code block

    :param max_results max number of results to show. -1 means no limit
    :param pattern filename pattern to profile. Eg. "module_name"
    
    :see https://docs.python.org/2/library/profile.html

    Example:
        with profiled():
            Session.query(FooClass).filter(FooClass.somevalue==8).all()
    Output:
        13726 function calls (13042 primitive calls) in 0.014 seconds

        Ordered by: cumulative time

        ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        222/21    0.001    0.000    0.011    0.001 lib/sqlalchemy/orm/loading.py:26(instances)
        220/20    0.002    0.000    0.010    0.001 lib/sqlalchemy/orm/loading.py:327(_instance)
           20    0.000    0.000    0.010    0.000 lib/sqlalchemy/orm/strategies.py:987(load_collection_from_subq)
            1    0.000    0.000    0.009    0.009 lib/sqlalchemy/orm/strategies.py:940(_load)
        ...
    """
    pr = cProfile.Profile()
    pr.enable()
    yield
    pr.disable()
    s = io.StringIO()
    ps = pstats.Stats(pr, stream=s).sort_stats("cumulative")
    ps.print_stats(max_results, pattern)
    print(s.getvalue())