def assoc(d, key, val):
    d = d.copy()
    d[key] = val
    return d
Handle one request, without blocking.
dataset/ETHPy150Open sympy/sympy/sympy/unify/core.py/assoc--crossover with--dataset/ETHPy150Open AppScale/appscale/AppServer/lib/django-1.5/django/test/testcases.py/StoppableWSGIServer._handle_request_noblock