James Benson JamesOBenson

Transforming Code into Beautiful, Idiomatic Python

Notes from Raymond Hettinger's talk at pycon US 2013 video, slides.

The code examples and direct quotes are all from Raymond's talk. I've reproduced them here for my own edification and the hopes that others will find them as handy as I have!

Looping over a range of numbers

for i in [0, 1, 2, 3, 4, 5]:

	#!/bin/bash
	MYDNS="8.8.8.8"
	DATE=$(date '+%Y-%m-%d')
	UBUNTU1_URL="http://cloud-images.ubuntu.com/xenial/current/xenial-server-cloudimg-amd64-disk1.img"
	UBUNTU2_URL="http://cloud-images.ubuntu.com/bionic/current/bionic-server-cloudimg-amd64.img"
	CIRROS_URL="http://download.cirros-cloud.net/0.4.0/cirros-0.4.0-x86_64-disk.img"
	CENTOS_URL="http://cloud.centos.org/centos/7/images/CentOS-7-x86_64-GenericCloud.qcow2c"
	VOLUME_SIZE=10
	NEW_VOLUME_SIZE=15
	VOLUME_NAME=$(cat /proc/sys/kernel/random/uuid)

	__author__ = 'Cody Giles'
	__license__ = "Creative Commons Attribution-ShareAlike 3.0 Unported License"
	__version__ = "1.0"
	__maintainer__ = "Cody Giles"
	__status__ = "Production"

	import subprocess
	import smtplib
	from email.mime.text import MIMEText
	import datetime

	# Python's list comprehensions are awesome.

	vals = [expression
	for value in collection
	if condition]

	# This is equivalent to:

	vals = []
	for value in collection:

	import json
	import yaml
	import boto3

	gg = boto3.client('greengrass')
	iot = boto3.client('iot')

	group = gg.create_group(Name="my_group")

	keys_cert = iot.create_keys_and_certificate(setAsActive=True)

	Input math equation and round to 3 decimals:
	printf %.3f $(echo "$exp" \| bc -l)

	Comparing 3 numbers to find equals/differences:
	read x
	read y
	read z
	if [[ "$x" -eq "$y" ]] && [[ "$x" -eq "$z" ]] ; then echo EQUILATERAL
	elif [[ "$x" -eq "$y" ]] \|\| [[ "$x" -eq "$z" ]] \|\| [[ "$y" -eq "$z" ]] ; then echo ISOSCELES
	else echo SCALENE

	#!/bin/bash

	# This script creates all necessary components to start booting VM's in openstack. This includes
	# - Project
	# - User
	# - Networking, subnets, router,
	# Security group allows
	# - 22 (SSH)
	# - IMPI (Ping test)
	# - 8443 & 8883 (Greengrass rules)

	#!/bin/bash
	source openrc

	timeout=10

	# pip install python-openstackclient
	# pip install python-novaclient
	# pip install python-glanceclient
	# This script will create and download all available images in an openstack cluster under a specific username.
	# This script has been tested against shellcheck and verified to the best of my abilities to work under any version of shell.

	# To deploy in Openstack ubuntu server LTS instance:
	sudo apt-add-repository ppa:ubuntu-lxc/stable -y

	# Using the backports will be supported after the end of 2017, snap is still being developed. As of Nov 28, 2017, backports and regular install are the same.
	sudo apt update && sudo apt install -y -t xenial-backports lxd lxd-client
	#sudo apt update && sudo apt install -y lxd lxd-client

	lxd init --auto
	# MTU of 1450 is needed for openstack VM.
	lxc network create lxdbr0 ipv4.address=auto ipv4.nat=true ipv6.address=none ipv6.nat=false bridge.mtu=1450

	#!/bin/sh

	# USE ON MASTER NODE as UBUNTU/root:

	export MASTER1="r2-710-01"
	export MASTER2="r2-710-03"
	export MASTER3="r2-710-05"
	export CLIENT_NODES="r2-710-07 r2-710-09 r2-710-11 r2-710-13"
	export ALL_NODES="r2-710-01 r2-710-03 r2-710-05 r2-710-07 r2-710-09 r2-710-11 r2-710-13"