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import string
import random


# The random module also provides the SystemRandom class which uses the system function
# os.urandom() to generate random numbers from sources provided by the operating system.
os_random = random.SystemRandom()
default_characters = string.ascii_letters + string.digits  # 62 characters

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System Design

Summary

A strong process is crucial to successfully solving system design questions. We broke it down into four steps:

• Scope the problem: Don't make assumptions; Ask questions; Understand the constraints and use cases.
• Sketch up an abstract design that illustrates the basic components of the system and the relationships between them.
• Think about the bottlenecks these components face when the system scales.
• Address these bottlenecks by using the fundamentals principles of scalable system design.

The fallacies of distributed systems

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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

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## Consistency?
### Weak
- After a write, reads may or may not see it
- Best effort only
- Memcached
- VoIP, live online video
- Online multiplayer games

### Eventual
- After a write, reads will eventually see it

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nvm install node --reinstall-packages-from=node

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#include "mainwindow.h"
#include <QApplication>
#include <QCoreApplication>

int main(int argc, char *argv[])
{
	QApplication a(argc, argv);
    QCoreApplication::setAttribute(Qt::AA_DontUseNativeMenuBar, true);
	MainWindow w;
	w.show();

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(def IPaddress "XX.XX.XX.XX")
(def port 1234)

(def socket (Socket. IPaddress port))
(println "Connected:" (.isConnected socket))
(def in (DataInputStream. (BufferedInputStream. (.getInputStream socket))))
(def out (DataOutputStream. (BufferedOutputStream. (.getOutputStream socket))))
(def command "Some string")
(println "Input:" command)
(.writeUTF out command)

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class Shark:
	shark_type = "White Shark" 		# class variable
	
	def __init__(self, name): 
    	print("I am being constructed!")
		self.name = name 		# instance variable

	def swim(self):
    	print("The shark is swimming.")

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age = 31.67

"Renzo ist ein {0} {1}, der in {country:*^20} wohnt. Er ist {2:.1f} Jahre alt.".format("sympatischer", "Mensch", age, country="Chile")
=> 'Renzo ist ein sympathischer Mann, der in *******Chile******** wohnt. Er ist 31.7 Jahre alt.'

for i in range(3,13):
    print("{:6d} {:6d} {:6d}".format(i, i*i, i*i*i))

=>
     3      9     27

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// @flow
import React from 'react';
import styled from 'styled-components';

type GlobalCssValues = 'initial' | 'inherit' | 'unset';

type WrapValue = 'nowrap' | 'wrap' | 'wrap-reverse' | GlobalCssValues;

type JustifyValue =
  | 'center'