item_20.py

#!/usr/bin/env python3

# 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 time import sleep
from datetime import datetime

def log(message, when=datetime.now()):
    print('%s: %s' % (when, message))

log('Hi there!')
sleep(0.1)
log('Hi again!')


# Example 2
def log(message, when=None):
    """Log a message with a timestamp.

    Args:
        message: Message to print.
        when: datetime of when the message occurred.
            Defaults to the present time.
    """
    when = datetime.now() if when is None else when
    print('%s: %s' % (when, message))


# Example 3
log('Hi there!')
sleep(0.1)
log('Hi again!')


# Example 4
import json

def decode(data, default={}):
    try:
        return json.loads(data)
    except ValueError:
        return default


# Example 5
foo = decode('bad data')
foo['stuff'] = 5
bar = decode('also bad')
bar['meep'] = 1
print('Foo:', foo)
print('Bar:', bar)


# Example 6
assert foo is bar


# Example 7
def decode(data, default=None):
    """Load JSON data from a string.

    Args:
        data: JSON data to decode.
        default: Value to return if decoding fails.
            Defaults to an empty dictionary.
    """
    if default is None:
        default = {}
    try:
        return json.loads(data)
    except ValueError:
        return default


# Example 8
foo = decode('bad data')
foo['stuff'] = 5
bar = decode('also bad')
bar['meep'] = 1
print('Foo:', foo)
print('Bar:', bar)