effectivepython/example_code/item_57.py at master · sharc007/effectivepython · GitHub

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#!/usr/bin/env PYTHONHASHSEED=1234 python3

# 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 threading import Lock

ALIVE = '*'

EMPTY = '-'

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

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 2

from threading import Thread

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 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 step_cell(y, x, get, set):

state = get(y, x)

neighbors = count_neighbors(y, x, get)

next_state = game_logic(state, neighbors)

set(y, x, next_state)

def simulate_threaded(grid):

next_grid = LockingGrid(grid.height, grid.width)

threads = []

for y in range(grid.height):

for x in range(grid.width):

args = (y, x, grid.get, next_grid.set)

thread = Thread(target=step_cell, args=args)

thread.start() # Fan out

threads.append(thread)

for thread in threads:

thread.join() # Fan in

return next_grid

# Example 3

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 = LockingGrid(5, 9) # Changed

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_threaded(grid) # Changed

print(columns)

# Example 4

def game_logic(state, neighbors):

raise OSError('Problem with I/O')

# Example 5

import contextlib

import io

fake_stderr = io.StringIO()

with contextlib.redirect_stderr(fake_stderr):

thread = Thread(target=game_logic, args=(ALIVE, 3))

thread.start()

thread.join()

print(fake_stderr.getvalue())

effectivepython/example_code/item_57.py at master · sharc007/effectivepython · GitHub

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