Abirdcfly

One-line Tree in Python

Using Python's built-in defaultdict we can easily define a tree data structure:

def tree(): return defaultdict(tree)

That's it!

Latency numbers every programmer should know

L1 cache reference ......................... 0.5 ns
Branch mispredict ............................ 5 ns
L2 cache reference ........................... 7 ns
Mutex lock/unlock ........................... 25 ns
Main memory reference ...................... 100 ns             
Compress 1K bytes with Zippy ............. 3,000 ns  =   3 µs
Send 2K bytes over 1 Gbps network ....... 20,000 ns  =  20 µs
SSD random read ........................ 150,000 ns  = 150 µs

Read 1 MB sequentially from memory ..... 250,000 ns = 250 µs

Routing tips for VPNs on OS X

When VPNs Just Work™, they're a fantastic way of allowing access to a private network from remote locations. When they don't work it can be an experience in frustration. I've had situations where I can connect to a VPN from my Mac, but various networking situations cause routing conflicts. Here are a couple of cases and how I've been able to get around them.

Specific cases

Case 1: conflicting additional routes.

In this example the VPN we are connecting to has a subnet that does not conflict with our local IP, but has additional routes that conflict in some way with our local network's routing. In my example the remote subnet is 10.0.x.0/24, my local subnet is 10.0.y.0/24, and the conflicting route is 10.0.0.0/8. Without the later route, I can't access all hosts on the VPN without manually adding the route after connecting to the VPN:

V2EX API Documents

Site

site/stats.json

URL: http://www.v2ex.com/api/site/stats.json

获取社区统计信息。

Installing SSHPASS

SSHPass is a tiny utility, which allows you to provide the ssh password without using the prompt. This will very helpful for scripting. SSHPass is not good to use in multi-user environment. If you use SSHPass on your development machine, it don't do anything evil.

Installing on Ubuntu

apt-get install sshpass

Installing on OS X

#参考资料

###下载单个文件，默认将输出打印到标准输出中(STDOUT)中

curl http://www.centos.org

	#! /usr/bin/env python2.7
	#encoding:utf-8
	#@description:一个python守护进程的例子
	#@tags:python,daemon
	import sys
	import os
	import time
	import atexit
	from signal import SIGTERM

	from flask import Flask
	from flask.ext.sqlalchemy import SQLAlchemy

	from flask.ext import admin, wtf
	from flask.ext.admin.contrib import sqlamodel

	app = Flask(__name__)
	app.config['SECRET_KEY'] = '123456790'
	app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.sqlite'
	db = SQLAlchemy(app)

	def fib(n):
	if n <= 2:
	return 1
	else:
	return fib(n-1) + fib(n-2)

	# --coding: utf-8 --
	import sys
	import os

	num = sys.argv[1] # num is the amount of *.ts files


	def add(x):
	"""'x' is the amount of *.ts
	This function should add all other .ts combined into '1.ts'