item_34.py

#!/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
import math

def wave(amplitude, steps):
    step_size = 2 * math.pi / steps
    for step in range(steps):
        radians = step * step_size
        fraction = math.sin(radians)
        output = amplitude * fraction
        yield output


# Example 2
def transmit(output):
    if output is None:
        print(f'Output is None')
    else:
        print(f'Output: {output:>5.1f}')

def run(it):
    for output in it:
        transmit(output)

run(wave(3.0, 8))


# Example 3
def my_generator():
    received = yield 1
    print(f'received = {received}')

it = my_generator()
output = next(it)       # Get first generator output
print(f'output = {output}')

try:
    next(it)            # Run generator until it exits
except StopIteration:
    pass
else:
    assert False


# Example 4
it = my_generator()
output = it.send(None)  # Get first generator output
print(f'output = {output}')

try:
    it.send('hello!')   # Send value into the generator
except StopIteration:
    pass
else:
    assert False


# Example 5
def wave_modulating(steps):
    step_size = 2 * math.pi / steps
    amplitude = yield             # Receive initial amplitude
    for step in range(steps):
        radians = step * step_size
        fraction = math.sin(radians)
        output = amplitude * fraction
        amplitude = yield output  # Receive next amplitude


# Example 6
def run_modulating(it):
    amplitudes = [
        None, 7, 7, 7, 2, 2, 2, 2, 10, 10, 10, 10, 10]
    for amplitude in amplitudes:
        output = it.send(amplitude)
        transmit(output)

run_modulating(wave_modulating(12))


# Example 7
def complex_wave():
    yield from wave(7.0, 3)
    yield from wave(2.0, 4)
    yield from wave(10.0, 5)

run(complex_wave())


# Example 8
def complex_wave_modulating():
    yield from wave_modulating(3)
    yield from wave_modulating(4)
    yield from wave_modulating(5)

run_modulating(complex_wave_modulating())


# Example 9
def wave_cascading(amplitude_it, steps):
    step_size = 2 * math.pi / steps
    for step in range(steps):
        radians = step * step_size
        fraction = math.sin(radians)
        amplitude = next(amplitude_it)  # Get next input
        output = amplitude * fraction
        yield output


# Example 10
def complex_wave_cascading(amplitude_it):
    yield from wave_cascading(amplitude_it, 3)
    yield from wave_cascading(amplitude_it, 4)
    yield from wave_cascading(amplitude_it, 5)


# Example 11
def run_cascading():
    amplitudes = [7, 7, 7, 2, 2, 2, 2, 10, 10, 10, 10, 10]
    it = complex_wave_cascading(iter(amplitudes))
    for amplitude in amplitudes:
        output = next(it)
        transmit(output)

run_cascading()