keenhenry

PyCon 2012 Digest

from DevOps team {rduplain,mattd,teebes}, to mobile developers at WillowTree Apps

Pronunciation

keenhenry

While attempting to explain JavaScript's reduce method on arrays, conceptually, I came up with the following - hopefully it's helpful; happy to tweak it if anyone has suggestions.

Intro

JavaScript Arrays have lots of built in methods on their prototype. Some of them mutate - ie, they change the underlying array in-place. Luckily, most of them do not - they instead return an entirely distinct array. Since arrays are conceptually a contiguous list of items, it helps code clarity and maintainability a lot to be able to operate on them in a "functional" way. (I'll also insist on referring to an array as a "list" - although in some languages, List is a native data type, in JS and this post, I'm referring to the concept. Everywhere I use the word "list" you can assume I'm talking about a JS Array) This means, to perform a single operation on the list as a whole ("atomically"), and to return a new list - thus making it much simpler to think about both the old list and the new one, what they contain, and

keenhenry

PROCESS STATE CODES
       Here are the different values that the s, stat and state output specifiers (header "STAT" or "S") will display to describe the state of a process:

               D    uninterruptible sleep (usually IO)
               R    running or runnable (on run queue)
               S    interruptible sleep (waiting for an event to complete)
               T    stopped, either by a job control signal or because it is being traced
               W    paging (not valid since the 2.6.xx kernel)
               X    dead (should never be seen)
               Z    defunct ("zombie") process, terminated but not reaped by its parent

keenhenry

// --- Compiling ---
$ wget http://download.redis.io/releases/redis-2.8.3.tar.gz
$ tar xzvf redis-2.8.3.tar.gz
$ cd redis-2.8.3
$ make
$ make install

// --- or using yum ---
$ rpm -Uvh http://download.fedoraproject.org/pub/epel/6/x86_64/epel-release-6-8.noarch.rpm
$ rpm -Uvh http://rpms.famillecollet.com/enterprise/remi-release-6.rpm

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

import sys

def inner():
    d = {'b': 1}
    try:
        d['a']
    except:

keenhenry

=== What is the best branching strategy for your team:

• Github flow - http://scottchacon.com/2011/08/31/github-flow.html

=== How to create pull request:

• git request-pull - https://git-scm.com/docs/git-request-pull
• And a better pull request by Atlasian - https://developer.atlassian.com/blog/2015/01/a-better-pull-request/

=== Good Practices using Git:

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#!/usr/bin/env python
# -*- coding: utf-8 -*-

from __future__ import print_function

import errno
import os

def mkdir_p(path):
    try:

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#!/bin/bash

export FOO=100

python - <<END

import os
print "foo:", os.environ['FOO']

END

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#!/usr/bin/env python

# name binding always creates a name in the local scope
ng = 'a global'
def f():
    # without the following commented out line, UnboundLocalError will throw
    # global ng
    nl = 2
    print ng, nl
    ng = 3

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Latency Comparison Numbers
--------------------------
L1 cache reference                           0.5 ns
Branch mispredict                            5   ns
L2 cache reference                           7   ns                      14x L1 cache
Mutex lock/unlock                           25   ns
Main memory reference                      100   ns                      20x L2 cache, 200x L1 cache
Compress 1K bytes with Zippy             3,000   ns        3 us
Send 1K bytes over 1 Gbps network       10,000   ns       10 us
Read 4K randomly from SSD*             150,000   ns      150 us          ~1GB/sec SSD