James Wang j-wang

3 hidden Python tips 🐍

Hidden from beginner tutorials and seldom found in books.

1. You can multiply a string to repeated it:

>>> "HOOLI-"*2
'HOOLI-HOOLI-'

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

	/**
	* Making promises
	*/
	let okPromise = Js.Promise.make((~resolve, ~reject as _) => [@bs] resolve("ok"));

	/* Simpler promise creation for static values */
	Js.Promise.resolve("easy");

	Js.Promise.reject(Invalid_argument("too easy"));

	import (
	"crypto/md5"
	"encoding/hex"
	)

	func GetMD5Hash(text string) string {
	hasher := md5.New()
	hasher.Write([]byte(text))
	return hex.EncodeToString(hasher.Sum(nil))
	}

	################################################################################
	# showdata.py
	#
	# Display analog data from Arduino using Python (matplotlib)
	#
	# electronut.in
	#
	################################################################################

	import sys, serial