effectivepython/example_code/item_45.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 datetime import datetime, timedelta

class Bucket:

def __init__(self, period):

self.period_delta = timedelta(seconds=period)

self.reset_time = datetime.now()

self.quota = 0

def __repr__(self):

return f'Bucket(quota={self.quota})'

bucket = Bucket(60)

print(bucket)

# Example 2

def fill(bucket, amount):

now = datetime.now()

if (now - bucket.reset_time) > bucket.period_delta:

bucket.quota = 0

bucket.reset_time = now

bucket.quota += amount

# Example 3

def deduct(bucket, amount):

now = datetime.now()

if (now - bucket.reset_time) > bucket.period_delta:

return False # Bucket hasn't been filled this period

if bucket.quota - amount < 0:

return False # Bucket was filled, but not enough

bucket.quota -= amount

return True # Bucket had enough, quota consumed

# Example 4

bucket = Bucket(60)

fill(bucket, 100)

print(bucket)

# Example 5

if deduct(bucket, 99):

print('Had 99 quota')

else:

print('Not enough for 99 quota')

print(bucket)

# Example 6

if deduct(bucket, 3):

print('Had 3 quota')

else:

print('Not enough for 3 quota')

print(bucket)

# Example 7

class NewBucket:

def __init__(self, period):

self.period_delta = timedelta(seconds=period)

self.reset_time = datetime.now()

self.max_quota = 0

self.quota_consumed = 0

def __repr__(self):

return (f'NewBucket(max_quota={self.max_quota}, '

f'quota_consumed={self.quota_consumed})')

# Example 8

@property

def quota(self):

return self.max_quota - self.quota_consumed

# Example 9

@quota.setter

def quota(self, amount):

delta = self.max_quota - amount

if amount == 0:

# Quota being reset for a new period

self.quota_consumed = 0

self.max_quota = 0

elif delta < 0:

# Quota being filled for the new period

assert self.quota_consumed == 0

self.max_quota = amount

else:

# Quota being consumed during the period

assert self.max_quota >= self.quota_consumed

self.quota_consumed += delta

# Example 10

bucket = NewBucket(60)

print('Initial', bucket)

fill(bucket, 100)

print('Filled', bucket)

if deduct(bucket, 99):

print('Had 99 quota')

else:

print('Not enough for 99 quota')

print('Now', bucket)

if deduct(bucket, 3):

print('Had 3 quota')

else:

print('Not enough for 3 quota')

print('Still', bucket)

effectivepython/example_code/item_45.py at master · sharc007/effectivepython · GitHub

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