This repository was archived by the owner on Oct 4, 2020. It is now read-only.
forked from bslatkin/effectivepython
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathitem_58.py
More file actions
executable file
·413 lines (332 loc) · 10 KB
/
item_58.py
File metadata and controls
executable file
·413 lines (332 loc) · 10 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
#!/usr/bin/env PYTHONHASHSEED=1234 python3
# Copyright 2014-2019 Brett Slatkin, Pearson Education Inc.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
# Reproduce book environment
import random
random.seed(1234)
import logging
from pprint import pprint
from sys import stdout as STDOUT
# Write all output to a temporary directory
import atexit
import gc
import io
import os
import tempfile
TEST_DIR = tempfile.TemporaryDirectory()
atexit.register(TEST_DIR.cleanup)
# Make sure Windows processes exit cleanly
OLD_CWD = os.getcwd()
atexit.register(lambda: os.chdir(OLD_CWD))
os.chdir(TEST_DIR.name)
def close_open_files():
everything = gc.get_objects()
for obj in everything:
if isinstance(obj, io.IOBase):
obj.close()
atexit.register(close_open_files)
# Example 1
from queue import Queue
class ClosableQueue(Queue):
SENTINEL = object()
def close(self):
self.put(self.SENTINEL)
def __iter__(self):
while True:
item = self.get()
try:
if item is self.SENTINEL:
return # Cause the thread to exit
yield item
finally:
self.task_done()
in_queue = ClosableQueue()
out_queue = ClosableQueue()
# Example 2
from threading import Thread
class StoppableWorker(Thread):
def __init__(self, func, in_queue, out_queue, **kwargs):
super().__init__(**kwargs)
self.func = func
self.in_queue = in_queue
self.out_queue = out_queue
def run(self):
for item in self.in_queue:
result = self.func(item)
self.out_queue.put(result)
def game_logic(state, neighbors):
# Do some blocking input/output in here:
data = my_socket.recv(100)
def game_logic(state, neighbors):
if state == ALIVE:
if neighbors < 2:
return EMPTY # Die: Too few
elif neighbors > 3:
return EMPTY # Die: Too many
else:
if neighbors == 3:
return ALIVE # Regenerate
return state
def game_logic_thread(item):
y, x, state, neighbors = item
try:
next_state = game_logic(state, neighbors)
except Exception as e:
next_state = e
return (y, x, next_state)
# Start the threads upfront
threads = []
for _ in range(5):
thread = StoppableWorker(
game_logic_thread, in_queue, out_queue)
thread.start()
threads.append(thread)
# Example 3
ALIVE = '*'
EMPTY = '-'
class SimulationError(Exception):
pass
class Grid:
def __init__(self, height, width):
self.height = height
self.width = width
self.rows = []
for _ in range(self.height):
self.rows.append([EMPTY] * self.width)
def get(self, y, x):
return self.rows[y % self.height][x % self.width]
def set(self, y, x, state):
self.rows[y % self.height][x % self.width] = state
def __str__(self):
output = ''
for row in self.rows:
for cell in row:
output += cell
output += '\n'
return output
def count_neighbors(y, x, get):
n_ = get(y - 1, x + 0) # North
ne = get(y - 1, x + 1) # Northeast
e_ = get(y + 0, x + 1) # East
se = get(y + 1, x + 1) # Southeast
s_ = get(y + 1, x + 0) # South
sw = get(y + 1, x - 1) # Southwest
w_ = get(y + 0, x - 1) # West
nw = get(y - 1, x - 1) # Northwest
neighbor_states = [n_, ne, e_, se, s_, sw, w_, nw]
count = 0
for state in neighbor_states:
if state == ALIVE:
count += 1
return count
def simulate_pipeline(grid, in_queue, out_queue):
for y in range(grid.height):
for x in range(grid.width):
state = grid.get(y, x)
neighbors = count_neighbors(y, x, grid.get)
in_queue.put((y, x, state, neighbors)) # Fan out
in_queue.join()
out_queue.close()
next_grid = Grid(grid.height, grid.width)
for item in out_queue: # Fan in
y, x, next_state = item
if isinstance(next_state, Exception):
raise SimulationError(y, x) from next_state
next_grid.set(y, x, next_state)
return next_grid
# Example 4
try:
def game_logic(state, neighbors):
raise OSError('Problem with I/O in game_logic')
simulate_pipeline(Grid(1, 1), in_queue, out_queue)
except:
logging.exception('Expected')
else:
assert False
# Example 5
# Restore the working version of this function
def game_logic(state, neighbors):
if state == ALIVE:
if neighbors < 2:
return EMPTY # Die: Too few
elif neighbors > 3:
return EMPTY # Die: Too many
else:
if neighbors == 3:
return ALIVE # Regenerate
return state
class ColumnPrinter:
def __init__(self):
self.columns = []
def append(self, data):
self.columns.append(data)
def __str__(self):
row_count = 1
for data in self.columns:
row_count = max(
row_count, len(data.splitlines()) + 1)
rows = [''] * row_count
for j in range(row_count):
for i, data in enumerate(self.columns):
line = data.splitlines()[max(0, j - 1)]
if j == 0:
padding = ' ' * (len(line) // 2)
rows[j] += padding + str(i) + padding
else:
rows[j] += line
if (i + 1) < len(self.columns):
rows[j] += ' | '
return '\n'.join(rows)
grid = Grid(5, 9)
grid.set(0, 3, ALIVE)
grid.set(1, 4, ALIVE)
grid.set(2, 2, ALIVE)
grid.set(2, 3, ALIVE)
grid.set(2, 4, ALIVE)
columns = ColumnPrinter()
for i in range(5):
columns.append(str(grid))
grid = simulate_pipeline(grid, in_queue, out_queue)
print(columns)
for thread in threads:
in_queue.close()
for thread in threads:
thread.join()
# Example 6
def count_neighbors(y, x, get):
# Do some blocking input/output in here:
data = my_socket.recv(100)
# Example 7
def count_neighbors(y, x, get):
n_ = get(y - 1, x + 0) # North
ne = get(y - 1, x + 1) # Northeast
e_ = get(y + 0, x + 1) # East
se = get(y + 1, x + 1) # Southeast
s_ = get(y + 1, x + 0) # South
sw = get(y + 1, x - 1) # Southwest
w_ = get(y + 0, x - 1) # West
nw = get(y - 1, x - 1) # Northwest
neighbor_states = [n_, ne, e_, se, s_, sw, w_, nw]
count = 0
for state in neighbor_states:
if state == ALIVE:
count += 1
return count
def count_neighbors_thread(item):
y, x, state, get = item
try:
neighbors = count_neighbors(y, x, get)
except Exception as e:
neighbors = e
return (y, x, state, neighbors)
def game_logic_thread(item):
y, x, state, neighbors = item
if isinstance(neighbors, Exception):
next_state = neighbors
else:
try:
next_state = game_logic(state, neighbors)
except Exception as e:
next_state = e
return (y, x, next_state)
from threading import Lock
class LockingGrid(Grid):
def __init__(self, height, width):
super().__init__(height, width)
self.lock = Lock()
def __str__(self):
with self.lock:
return super().__str__()
def get(self, y, x):
with self.lock:
return super().get(y, x)
def set(self, y, x, state):
with self.lock:
return super().set(y, x, state)
# Example 8
in_queue = ClosableQueue()
logic_queue = ClosableQueue()
out_queue = ClosableQueue()
threads = []
for _ in range(5):
thread = StoppableWorker(
count_neighbors_thread, in_queue, logic_queue)
thread.start()
threads.append(thread)
for _ in range(5):
thread = StoppableWorker(
game_logic_thread, logic_queue, out_queue)
thread.start()
threads.append(thread)
# Example 9
def simulate_phased_pipeline(
grid, in_queue, logic_queue, out_queue):
for y in range(grid.height):
for x in range(grid.width):
state = grid.get(y, x)
item = (y, x, state, grid.get)
in_queue.put(item) # Fan out
in_queue.join()
logic_queue.join() # Pipeline sequencing
out_queue.close()
next_grid = LockingGrid(grid.height, grid.width)
for item in out_queue: # Fan in
y, x, next_state = item
if isinstance(next_state, Exception):
raise SimulationError(y, x) from next_state
next_grid.set(y, x, next_state)
return next_grid
# Example 10
grid = LockingGrid(5, 9)
grid.set(0, 3, ALIVE)
grid.set(1, 4, ALIVE)
grid.set(2, 2, ALIVE)
grid.set(2, 3, ALIVE)
grid.set(2, 4, ALIVE)
columns = ColumnPrinter()
for i in range(5):
columns.append(str(grid))
grid = simulate_phased_pipeline(
grid, in_queue, logic_queue, out_queue)
print(columns)
for thread in threads:
in_queue.close()
for thread in threads:
logic_queue.close()
for thread in threads:
thread.join()
# Example 11
# Make sure exception propagation works as expected
def count_neighbors(*args):
raise OSError('Problem with I/O in count_neighbors')
in_queue = ClosableQueue()
logic_queue = ClosableQueue()
out_queue = ClosableQueue()
threads = [
StoppableWorker(
count_neighbors_thread, in_queue, logic_queue,
daemon=True),
StoppableWorker(
game_logic_thread, logic_queue, out_queue,
daemon=True),
]
for thread in threads:
thread.start()
try:
simulate_phased_pipeline(
grid, in_queue, logic_queue, out_queue)
except SimulationError:
pass # Expected
else:
assert False