update from Atlas

15-context-mngr/mirror.py

@@ -15,6 +15,8 @@ While active, the context manager reverses text output to
     YKCOWREBBAJ
     >>> what  # <4>
     'JABBERWOCKY'
+    >>> print('Back to normal.')  # <5>
+    Back to normal.
 
 # END MIRROR_DEMO_1
 

16-coroutine/coroaverager3.py

@@ -75,7 +75,7 @@ def main(data):  # <8>
         next(group)  # <10>
         for value in values:
             group.send(value)  # <11>
-        group.send(None)  # <12>
+        group.send(None)  # important! <12>
 
     # print(results)  # uncomment to debug
     report(results)

16-coroutine/yield_from_expansion_simplified.py

@@ -0,0 +1,32 @@
+# Code below is a very simplified expansion of the statement:
+#
+# RESULT = yield from EXPR
+#
+# This code assumes that the subgenerator will run to completion,
+# without the client ever calling ``.throw()`` or ``.close()``.
+# Also, this code makes no distinction between the client
+# calling ``next(subgen)`` or ``subgen.send(...)``
+#
+# The full expansion is in:
+# PEP 380 -- Syntax for Delegating to a Subgenerator
+#
+# https://www.python.org/dev/peps/pep-0380/#formal-semantics
+
+
+# BEGIN YIELD_FROM_EXPANSION_SIMPLIFIED
+_i = iter(EXPR)  # <1>
+try:
+    _y = next(_i)  # <2>
+except StopIteration as _e:
+    _r = _e.value  # <3>
+else:
+    while 1:  # <4>
+        _s = yield _y  # <5>
+        try:
+            _y = _i.send(_s)  # <6>
+        except StopIteration as _e:  # <7>
+            _r = _e.value
+            break
+
+RESULT = _r  # <8>
+# END YIELD_FROM_EXPANSION_SIMPLIFIED

control/referencias.txt

@@ -1,12 +0,0 @@
-What's New in Python 2.5 - PEP 342: New Generator Features
-http://docs.python.org/release/2.5/whatsnew/pep-342.html
-
-PEP 342 -- Coroutines via Enhanced Generators
-http://www.python.org/dev/peps/pep-0342/
-
-PEP 380 -- Syntax for Delegating to a Subgenerator
-http://www.python.org/dev/peps/pep-0380/
-
-Coroutines For the Working Python Developer
-http://sdiehl.github.io/coroutine-tutorial/
-

control/taxi_sim3.py

@@ -0,0 +1,281 @@
+"""
+Taxi simulator
+
+Sample run with two cars, random seed 10. This is a valid doctest.
+
+    >>> main(num_taxis=2, seed=10)
+    taxi: 0  Event(time=0, proc=0, action='leave garage')
+    taxi: 0  Event(time=4, proc=0, action='pick up passenger')
+    taxi: 1     Event(time=5, proc=1, action='leave garage')
+    taxi: 1     Event(time=9, proc=1, action='pick up passenger')
+    taxi: 0  Event(time=10, proc=0, action='drop off passenger')
+    taxi: 1     Event(time=12, proc=1, action='drop off passenger')
+    taxi: 0  Event(time=17, proc=0, action='pick up passenger')
+    taxi: 1     Event(time=19, proc=1, action='pick up passenger')
+    taxi: 1     Event(time=21, proc=1, action='drop off passenger')
+    taxi: 1     Event(time=24, proc=1, action='pick up passenger')
+    taxi: 0  Event(time=28, proc=0, action='drop off passenger')
+    taxi: 1     Event(time=28, proc=1, action='drop off passenger')
+    taxi: 0  Event(time=29, proc=0, action='going home')
+    taxi: 1     Event(time=30, proc=1, action='pick up passenger')
+    taxi: 1     Event(time=61, proc=1, action='drop off passenger')
+    taxi: 1     Event(time=62, proc=1, action='going home')
+    *** end of events ***
+
+See explanation and longer sample run at the end of this module.
+
+"""
+
+import random
+import collections
+import queue
+import argparse
+import time
+
+DEFAULT_NUMBER_OF_TAXIS = 3
+DEFAULT_END_TIME = 180
+SEARCH_DURATION = 5
+TRIP_DURATION = 20
+DEPARTURE_INTERVAL = 5
+
+Event = collections.namedtuple('Event', 'time proc action')
+
+Actitivy = collections.namedtuple('Actitivy', 'name distr_param')
+
+START = Actitivy('start shift', TRIP_DURATION)
+SEARCH_PAX = Actitivy('searching for passenger', SEARCH_DURATION)
+DRIVE_PAX = Actitivy('driving passenger', TRIP_DURATION)
+
+TRANSITIONS = {
+    START : SEARCH_PAX;
+    SEARCH_PAX : DRIVE_PAX;
+}
+
+def compute_duration(previous_action):
+    """Compute action duration using exponential distribution"""
+    if previous_action in ['leave garage', 'drop off passenger']:
+        # state is prowling
+        interval = SEARCH_DURATION
+    elif previous_action == 'pick up passenger':
+        # state is trip
+        interval = TRIP_DURATION
+    elif previous_action == 'going home':
+        interval = 1
+    else:
+        assert False
+    return int(random.expovariate(1/interval)) + 1
+
+
+# BEGIN TAXI_PROCESS
+def taxi_process(ident, trips, start_time=0):  # <1>
+    """Yield to simulator issuing event at each state change"""
+    time = yield Event(start_time, ident, 'leave garage')  # <2>
+    for i in range(trips):  # <3>
+        time = yield Event(time, ident, 'pick up passenger')  # <4>
+        time = yield Event(time, ident, 'drop off passenger')  # <5>
+
+    yield Event(time, ident, 'going home')  # <6>
+    # end of taxi process # <7>
+# END TAXI_PROCESS
+
+
+# BEGIN TAXI_SIMULATOR
+class Simulator:
+
+    def __init__(self, procs_map):
+        self.events = queue.PriorityQueue()
+        self.procs = dict(procs_map)
+
+    def run(self, end_time, delay=False):  # <1>
+        """Schedule and display events until time is up"""
+        # schedule the first event for each cab
+        for _, proc in sorted(self.procs.items()):  # <2>
+            first_event = next(proc)  # <3>
+            self.events.put(first_event)  # <4>
+
+        # main loop of the simulation
+        sim_time = 0  # <5>
+        while sim_time < end_time:  # <6>
+            if self.events.empty():  # <7>
+                print('*** end of events ***')
+                break
+
+            # get and display current event
+            current_event = self.events.get()  # <8>
+            if delay:
+                time.sleep((current_event.time - sim_time) / 2)
+            # update the simulation time
+            sim_time, proc_id, previous_action = current_event
+            print('taxi:', proc_id, proc_id * '   ', current_event)
+            active_proc = self.procs[proc_id]
+            # schedule next action for current proc
+            next_time = sim_time + compute_duration(previous_action)
+            try:
+                next_event = active_proc.send(next_time)  # <12>
+            except StopIteration:
+                del self.procs[proc_id]  # <13>
+            else:
+                self.events.put(next_event)  # <14>
+        else:  # <15>
+            msg = '*** end of simulation time: {} events pending ***'
+            print(msg.format(self.events.qsize()))
+# END TAXI_SIMULATOR
+
+
+
+
+def main(end_time=DEFAULT_END_TIME, num_taxis=DEFAULT_NUMBER_OF_TAXIS,
+         seed=None, delay=False):
+    """Initialize random generator, build procs and run simulation"""
+    if seed is not None:
+        random.seed(seed)  # get reproducible results
+
+    taxis = {i: taxi_process(i, (i+1)*2, i*DEPARTURE_INTERVAL)
+             for i in range(num_taxis)}
+    sim = Simulator(taxis)
+    sim.run(end_time, delay)
+
+
+if __name__ == '__main__':
+
+    parser = argparse.ArgumentParser(
+                        description='Taxi fleet simulator.')
+    parser.add_argument('-e', '--end-time', type=int,
+                        default=DEFAULT_END_TIME,
+                        help='simulation end time; default = %s'
+                        % DEFAULT_END_TIME)
+    parser.add_argument('-t', '--taxis', type=int,
+                        default=DEFAULT_NUMBER_OF_TAXIS,
+                        help='number of taxis running; default = %s'
+                        % DEFAULT_NUMBER_OF_TAXIS)
+    parser.add_argument('-s', '--seed', type=int, default=None,
+                        help='random generator seed (for testing)')
+    parser.add_argument('-d', '--delay', action='store_true',
+                        help='introduce delay proportional to simulation time')
+
+    args = parser.parse_args()
+    main(args.end_time, args.taxis, args.seed, args.delay)
+
+
+"""
+Notes for the ``taxi_process`` coroutine::
+
+<1> `taxi_process` will be called once per taxi, creating a generator
+    object to represent its operations. `ident` is the number of the taxi
+    (eg. 0, 1, 2 in the sample run); `trips` is the number of trips this
+    taxi will make before going home; `start_time` is when the taxi
+    leaves the garage.
+
+<2> The first `Event` yielded is `'leave garage'`. This suspends the
+    coroutine, and lets the simulation main loop proceed to the next
+    scheduled event. When it's time to reactivate this process, the main
+    loop will `send` the current simulation time, which is assigned to
+    `time`.
+
+<3> This block will be repeated once for each trip.
+
+<4> The ending time of the search for a passenger is computed.
+
+<5> An `Event` signaling passenger pick up is yielded. The coroutine
+    pauses here. When the time comes to reactivate this coroutine,
+    the main loop will again `send` the current time.
+
+<6> The ending time of the trip is computed, taking into account the
+    current `time`.
+
+<7> An `Event` signaling passenger drop off is yielded. Coroutine
+    suspended again, waiting for the main loop to send the time of when
+    it's time to continue.
+
+<8> The `for` loop ends after the given number of trips, and a final
+    `'going home'` event is yielded, to happen 1 minute after the current
+    time. The coroutine will suspend for the last time. When reactivated,
+    it will be sent the time from the simulation main loop, but here I
+    don't assign it to any variable because it will not be useful.
+
+<9> When the coroutine falls off the end, the coroutine object raises
+    `StopIteration`.
+
+
+Notes for the ``Simulator.run`` method::
+
+<1> The simulation `end_time` is the only required argument for `run`.
+
+<2> Use `sorted` to retrieve the `self.procs` items ordered by the
+    integer key; we don't care about the key, so assign it to `_`.
+
+<3> `next(proc)` primes each coroutine by advancing it to the first
+    yield, so it's ready to be sent data. An `Event` is yielded.
+
+<4> Add each event to the `self.events` `PriorityQueue`. The first
+    event for each taxi is `'leave garage'`, as seen in the sample run
+    (ex_taxi_process>>).
+
+<5> Main loop of the simulation: run until the current `time` equals
+    or exceeds the `end_time`.
+
+<6> The main loop may also exit if there are no pending events in the
+    queue.
+
+<7> Get `Event` with the smallest `time` in the queue; this is the
+    `current_event`.
+
+<8> Display the `Event`, identifying the taxi and adding indentation
+    according to the taxi id.
+
+<9> Update the simulation time with the time of the `current_event`.
+
+<10> Retrieve the coroutine for this taxi from the `self.procs`
+     dictionary.
+
+<11> Send the `time` to the coroutine. The coroutine will yield the
+     `next_event` or raise `StopIteration` it's finished.
+
+<12> If `StopIteration` was raised, delete the coroutine from the
+     `self.procs` dictionary.
+
+<13> Otherwise, put the `next_event` in the queue.
+
+<14> If the loop exits because the simulation time passed, display the
+     number of events pending (which may be zero by coincidence,
+     sometimes).
+
+
+Sample run from the command line, seed=24, total elapsed time=160::
+
+# BEGIN TAXI_SAMPLE_RUN
+$ python3 taxi_sim.py -s 24 -e 160
+taxi: 0  Event(time=0, proc=0, action='leave garage')
+taxi: 0  Event(time=5, proc=0, action='pick up passenger')
+taxi: 1     Event(time=5, proc=1, action='leave garage')
+taxi: 1     Event(time=6, proc=1, action='pick up passenger')
+taxi: 2        Event(time=10, proc=2, action='leave garage')
+taxi: 2        Event(time=11, proc=2, action='pick up passenger')
+taxi: 2        Event(time=23, proc=2, action='drop off passenger')
+taxi: 0  Event(time=24, proc=0, action='drop off passenger')
+taxi: 2        Event(time=24, proc=2, action='pick up passenger')
+taxi: 2        Event(time=26, proc=2, action='drop off passenger')
+taxi: 0  Event(time=30, proc=0, action='pick up passenger')
+taxi: 2        Event(time=31, proc=2, action='pick up passenger')
+taxi: 0  Event(time=43, proc=0, action='drop off passenger')
+taxi: 0  Event(time=44, proc=0, action='going home')
+taxi: 2        Event(time=46, proc=2, action='drop off passenger')
+taxi: 2        Event(time=49, proc=2, action='pick up passenger')
+taxi: 1     Event(time=70, proc=1, action='drop off passenger')
+taxi: 2        Event(time=70, proc=2, action='drop off passenger')
+taxi: 2        Event(time=71, proc=2, action='pick up passenger')
+taxi: 2        Event(time=79, proc=2, action='drop off passenger')
+taxi: 1     Event(time=88, proc=1, action='pick up passenger')
+taxi: 2        Event(time=92, proc=2, action='pick up passenger')
+taxi: 2        Event(time=98, proc=2, action='drop off passenger')
+taxi: 2        Event(time=99, proc=2, action='going home')
+taxi: 1     Event(time=102, proc=1, action='drop off passenger')
+taxi: 1     Event(time=104, proc=1, action='pick up passenger')
+taxi: 1     Event(time=135, proc=1, action='drop off passenger')
+taxi: 1     Event(time=136, proc=1, action='pick up passenger')
+taxi: 1     Event(time=151, proc=1, action='drop off passenger')
+taxi: 1     Event(time=152, proc=1, action='going home')
+*** end of events ***
+# END TAXI_SAMPLE_RUN
+
+"""