# Copyright 2014 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.
# Preamble to mimick book environment
import logging
from pprint import pprint
from sys import stdout as STDOUT
# Example 1
from datetime import datetime, timedelta
class Bucket(object):
def __init__(self, period):
self.period_delta = timedelta(seconds=period)
self.reset_time = datetime.now()
self.quota = 0
def __repr__(self):
return 'Bucket(quota=%d)' % self.quota
bucket = Bucket(60)
print(bucket)
Bucket(quota=0)
# 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
if bucket.quota - amount < 0:
return False
bucket.quota -= amount
return True
# Example 4
bucket = Bucket(60)
fill(bucket, 100)
print(bucket)
Bucket(quota=100)
# Example 5
if deduct(bucket, 99):
print('Had 99 quota')
else:
print('Not enough for 99 quota')
print(bucket)
Had 99 quota Bucket(quota=1)
# Example 6
if deduct(bucket, 3):
print('Had 3 quota')
else:
print('Not enough for 3 quota')
print(bucket)
Not enough for 3 quota Bucket(quota=1)
# Example 7
class Bucket(object):
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 ('Bucket(max_quota=%d, quota_consumed=%d)' %
(self.max_quota, 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 = Bucket(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)
Initial Bucket(max_quota=0, quota_consumed=0) Filled Bucket(max_quota=100, quota_consumed=0) Had 99 quota Now Bucket(max_quota=100, quota_consumed=99) Not enough for 3 quota Still Bucket(max_quota=100, quota_consumed=99)