A quick reference guide for the Pythonista in the process of becoming a Rustacean

py2rs

From Python into Rust

let x = Rust::from("Python");

A quick reference guide for the Pythonista in process of becoming a Rustacean.

Monty Python - Season 3 - Episode 49

The sketch

Mrs. Jalin: George.
Mr. Jalin: Yes, Gladys.
Mrs. Jalin: There's a man at the door with a moustache.
Mr. Jalin: Tell him I've already got one. (Mrs. Jalin hits him hard with a newspaper) 
          All right, all right. What's he want then?
Mrs. Jalin: He says do we want a documentary on crustaceans.
Mr. Jalin: Crustaceans!
Mrs. Jalin: Yes.
Mr. Jalin: What's he mean, crustaceans?
Mrs. Jalin: CRUSTACEANS!! GASTROPODS! LAMELLIBRANCHS! CEPHALOPODS!
...

Ok... watch it later... let's learn some Rust now...

TOC

• Getting Started with Rust
• Where to exercice
• Where to be informed on news and updates
• Interacting with Rustacean Communities
• Additional learning Resources
• Curious Facts
• py2rs: Glossary of terms
• py2rs: General fact comparison
• py2rs: Environment Tools
• py2rs: Libraries and Frameworks
• py2rs: Applications
• py2rs: Useful Crates
• py2rs: Code comparison Python X Rust implementations
• Credits

Getting Started with Rust

Assuming you already know what is Rust and already decided to start learning it. Here are some steps for you to follow:

1. Take a tour of Rust Syntax and Coding Style
   https://learnxinyminutes.com/docs/rust/
2. Watch some screencasts to get basics of Ownership &Borrowing concept
   http://intorust.com/
3. Follow this set of runnable examples to understand how everything fit together
   https://rustbyexample.com
4. Now it is time to read your first book, you can pick:

   • Rust Essentials

     A good introduction to Rust language in a more superficial approach which results in a very pleasant and easy reading, recommended even for those who are not experienced with low level systems languages.

     • Paparback and e-book available on Packt Publisher
       https://www.packtpub.com/application-development/rust-essentials-second-edition

   • TRPL (The Rust Programming language Book)

     A complete Guide to Rust Language
     https://doc.rust-lang.org/book/

     • Official Book
     • Free to read online
     • Available as papaerback or e-book (buy at Amazon)
5. Read some real examples
   • Rust Cookbook
     https://rust-lang-nursery.github.io/rust-cookbook/ This Rust Cookbook is a collection of simple examples that demonstrate good practices to accomplish common programming tasks, using the crates of the Rust ecosystem.
   • Anthology
     https://github.com/brson/rust-anthology/blob/master/master-list.md
6. Patterns and Good Practices
   • Rust Patterns https://github.com/rust-unofficial/patterns
   • API Guidelines https://rust-lang-nursery.github.io/api-guidelines/

Exercises

Time to put your new knowledge in action solving some exercises.

1. Exercism.io
   Register a new account on exercism.io (using github auth)
   Install exercism command line client on your computer
   Solve some exercises: http://www.exercism.io/languages/rust/about

2. Rust Playground
   Run Live Rust Code in the browser with https://play.rust-lang.org/

Getting updated

Now I assume you are addicted to Rust and you want to be updated about everything around it, here are some good links to follow.

1. This Week in Rust Newsletter
   https://this-week-in-rust.org/
   https://twitter.com/thisweekinrust
2. Awesome Rust Newsletter
   https://rust.libhunt.com/
3. Reddit
   http://reddit.com/r/rust (serious sub-reddit)
   http://reddit.com/r/rustjerk (almost memes only)
4. Official Twitter
   https://twitter.com/rustlang

Interact with other Rustaceans

Don't be afraid, the Rustaceans are a very receptive species and are cozy with the Pythonistas.

Main Community links

https://www.rust-lang.org/en-US/community.html

Local Communities

• Brazil

  • General
    • Youtube : http://bit.ly/canalrustbr
    • Telegram: https://t.me/rustlangbr
  • Rust BH
    • https://t.me/rustbh

• Indonesia

  • General
    • FB Groups (Rustaceans Indonesia) : https://fb.com/groups/RustaceansID
    • FB Groups (Rust ID) : https://fb.com/groups/rustindo
    • Telegram (Rust Indonesia) : https://t.me/rustindonesia

• Add your country/city here, send a Pull Request.

Additional learning resources

• Rust Learning https://github.com/ctjhoa/rust-learning
• Rust Guidelines (WIP) https://aturon.github.io/
• Rust Design Patterns and Idioms https://github.com/rust-unofficial/patterns/
• Idiomatic Rust https://github.com/mre/idiomatic-rust
• GTK Rust Tutorial https://mmstick.github.io/gtkrs-tutorials/
• Effective use of iterators http://hermanradtke.com/2015/06/22/effectively-using-iterators-in-rust.html
• Red Hat Developers: Speed up Your Python with Rust https://developers.redhat.com/blog/2017/11/16/speed-python-using-rust/
• What's a reference in Rust? (The best article to understand 'lifetimes and &) https://jvns.ca/blog/2017/11/27/rust-ref/

Facts

• The language is named Rust because "rust is as close to the bare metal as you can get".,
  in metal theory rust is the chemical layer closest to bare metal.
  (also Wikipedia says that the name was possibly inspired by the name of a Fungi)
• The Rust trifecta is 1) Memory Safe, 2) Fast 3) Concurrent
• Rust can be used for web development http://www.arewewebyet.org/
• Rust can be used for Gaming Development http://arewegameyet.com/
• Rust can be used for Machine Learning http://www.arewelearningyet.com/
• Lots of IDEs and Editors supports Rust https://areweideyet.com/
  (VSCode is known to have the better support by now https://marketplace.visualstudio.com/items?itemName=kalitaalexey.vscode-rust)
• Rust packages are called Crates and are installed by Cargo explore them at http://crates.io
• In Rust there is no Class but Structs, Enums, Traits, functions and macros!
• Rust compiler was first writen in OCaml then rewritten in Rust! (Rust is writen Rust!!!)
• Rust type system is strongly inspired by Haskell
• Rust functional style is inspired by Erlang
• Rust type inference is inspired by Python and Ruby
• The main syntax style is inspired by C and C++
• There is no automated Garbage Collector so Rust frees memory based on Resource Aquisition RAII (a.k.a Ownership)
• Rust has Generic Types!!!
• As Rust is close to bare metal you can ship a program without the inclusion of Rust's runtime which makes easy to distribute programs (no need of dependencies and virtuelenvs management)
• There are Python code in Rust! Rust build is bootstrapped by Python
• Graydon Hoare (creator of Rust) is now working at Apple developing the Swift language
• Rust is the developers most loved language according to Stack Overflow Survey
• Rust is the most energy efficient language! and that is very important for environment, data center companies and maybe it can help saving your laptop and phone battery in near future.
• There is an Operating System written in Rust - https://www.redox-os.org/
• Mozilla released the fastest version of Firefox (quantum) having many parts written on Rust
• The Rust mascot (unofficial) is called Ferris and it is a crab http://www.rustacean.net/
  (There is no record of the official reason about being a crab, the reasonable history is that it was inspired by the Rusty Crab a common species of crab and also a name of a famous restaurant.)
• To compliment your fellow Rustaceans don't say cheers!. Say safe! (safe! is also said when toasting with champagne at Rust conferences)

More facts? and curiosities send a question here or send a Pull Request adding an interest fact to this list.

Glossary of terms

py2rs

From Python into Rust

let x = Rust::from("Python");

A quick reference guide for the Pythonista in process of becoming a Rustacean.

General

Environment Tools

Libraries and Frameworks

Applications

Useful crates

Add Pythonic features to Rust

Show me The code

From Python to Rust by examples

You can copy-paste and run the Rust examples in https://play.rust-lang.org/ and Python in https://repl.it/languages/python3

Creating a new project

Create a new project with basic files, entry points, module initializer, dependency and installation artifacts.

Python

$ mkdir {pyproject,pyproject/src}
$ touch {pyproject/src/{__init__.py,__main__.py,program.py},pyproject/{requirements.txt,setup.py}} 
$ echo "-e ." >> pyproject/requirements.txt
$ echo "from setuptools import setup" >> pyproject/setup.py
$ echo "setup(author=..., name=...)" >> pyproject/setup.py

Rust

$ cargo new my-rust-program

Installing new libraries/crates

Python

$ pip install foo 

Rust

$ cargo install foo

Running / Compiling

Python

$ python my_python_program.py 

Rust

$ cargo run

Hello World

Python

if __name__ == "__main__":
    print("Hello, World")

Rust

fn main() {
  println!("Hello, World");
}

Types and Declarations

Create new objects, values on basic primitive types and also data structures.

Python

age = 80
name = 'daffy'
weight = 62.3
loons = ['bugs', 'daffy', 'taz']
ages = {  # Ages for 2017
    'daffy': 80,
    'bugs': 79,
    'taz': 63,
}

Rust

use std::collections::HashMap;

fn main() {
    let age = 80;
    let name = "daffy";
    let weight = 62.3;
    let mut loons = vec!["bugs", "daffy", "taz"];

    let mut ages = HashMap::new();  // Ages for 2017
    ages.insert("daffy", 80);
    ages.insert("bugs", 79);
    ages.insert("taz", 63);
}

Define a function

Defining a function that takes 2 integer arguments and returns its sum.

Python

def add(a, b):
    """Adds a to b"""
    return a + b

Python with typing annotations

It looks more similar to Rust.

def add(a: int, b: int) -> int:
    """Adds a to b"""
    return a + b

Rust

// Adds a to b
fn add(a: i32, b: i32) -> i32 {
  a + b
}

List/Slice

Creating a list, adding new elements, gettings its length, slicing by index, itarating using for loop and iterating with enumerator.

Python

names = ['bugs', 'taz', 'tweety']
print(names[0])  # bugs
names.append('elmer')
print(len(names))  # 4
print(names[2:])  # ['tweety', 'elmer']

for name in names:
    print(name)

for i, name in enumerate(names):
    print('{} at {}'.format(name, i))

Rust

fn main() {
    let mut names = vec!["bugs", "taz", "tweety"];
    println!("{}", names[0]);  // bugs
    names.push("elmer");
    println!("{}", names.len());  // 4
    println!("{:?}", &names[2..]);  // ["tweety", "elmer"]

    for name in &names {
        println!("{}", name);
    }

    for (i, name) in names.iter().enumerate() {
        println!("{} at {}", i, name);
    }
}

Dict/Map

Create new dictionaries (hash maps), adding new keys and values, changing values, getting by key, checking if a key is containing, etc.

Python

# Creating a new dict and populating it
ages = {}
ages['daffy'] = 80
ages['bugs'] = 79
ages['taz'] = 63

# or doing the same using a for loop
ages = {}
for name, age in [("daffy", 80), ("bugs", 79), ("taz", 63)]:
    ages[name] = age

# or initializing from a list
ages = dict([("daffy", 80), ("bugs", 79), ("taz", 63)])

# or passing key values on creation
ages = {  # Ages for 2017
    'daffy': 80,
    'bugs': 79,
    'taz': 63,
}

ages['elmer'] = 80
print(ages['bugs'])  # 79
print('bugs' in ages)  # True

del ages['taz']

for name in ages:  # Keys
    print(name)

for name, age in ages.items():  # Keys & values
    print('{} is {} years old'.format(name, age))

Rust

use std::iter::FromIterator;
use std::collections::HashMap;

fn main() {

    // Creating a new HashMap and populating it
    let mut ages = HashMap::new();  // Ages for 2017
    ages.insert("daffy", 80);
    ages.insert("bugs", 79);
    ages.insert("taz", 63);

    // or doing the same using a loop
    let mut ages = HashMap::new();
    for &(name, age) in [("daffy", 80), ("bugs", 79), ("taz", 63)].iter() {
        // For non-Copy data, remove & and use iter().clone()
        ages.insert(name, age);
    }

    // or initializing from Array
    let mut ages: HashMap<&str, i32> =  // Ages for 2017
        [("daffy", 80), 
         ("bugs", 79), 
         ("taz", 63)]
        .iter().cloned().collect();

    // or initializing from Vec (Iterator)
    let mut ages: HashMap<&str, i32> =  // Ages for 2017
        HashMap::from_iter(
            vec![
               ("daffy", 80),
               ("bugs", 79),
               ("taz", 63)
            ]
        );

    ages.insert("elmer", 80);
    println!("{}", ages["bugs"]);  // 79
    println!("{}", ages.contains_key("bugs")); // true
    ages.remove("taz");


    for name in ages.keys() {  // Keys
      println!("{}", name);
    }

    for (name, age) in &ages {  // Keys & values
      println!("{} is {} years old", name, age);
    }

}

Pythonic alternative to dict/map in Rust

You can use the maplit crate to load hashmap! macro to have an efficient sugared (a.k.a Pythonic) syntax!

# Cargo.toml
[dependencies]
maplit = "*"

then

#[macro_use] extern crate maplit;

let map = hashmap!{
    "daffy" => 80,
    "bugs" => 79,
    "taz" => 63,
};

set / HashSet

Create a set (a hash of unique keys), add new keys and compute intersection, difference and union

Python

# creating and populating
colors = set()
colors.add("red")
colors.add("green")
colors.add("blue")
colors.add("blue")

# using literal syntax
colors = {'red', 'green', 'blue', 'blue'}

# from an iterator
colors = set(['red', 'green', 'blue', 'blue'])


# deduplication
print(colors)  # {"blue", "green", "red"}

# operations
colors = {'red', 'green', 'blue', 'blue'}
flag_colors = {"red", "black"}

# difference
colors.difference(flag_colors)  # {'blue', 'green'}

# symmetric difference
colors.symmetric_difference(flag_colors)  # {'black', 'blue', 'green'}

# intersection
colors.intersection(flag_colors)  # {'red'}

# unioin
colors.intersection(flag_colors)  # {'black', 'blue', 'green', 'red'}

Rust

use std::collections::HashSet;
use std::iter::FromIterator;

fn main() {

    // creating and populating - type inference
    let mut colors = HashSet::new();
    colors.insert("red");
    colors.insert("green");
    colors.insert("blue");
    colors.insert("blue");

    // from an iterator - explicit type
    let mut colors: HashSet<&str> = HashSet::from_iter(vec!["red", "green", "blue", "blue"]);

    // deduplication
    println!("{:?}", colors); // {"blue", "green", "red"}

    // Operations
    let mut colors: HashSet<&str> = HashSet::from_iter(vec!["red", "green", "blue", "blue"]);
    let mut flag_colors: HashSet<&str> = HashSet::from_iter(vec!["red", "black"]);

    // difference
    colors.difference(&flag_colors); // ["green", "blue"]

    // symmetric difference
    colors.symmetric_difference(&flag_colors); // ["blue", "green", "black"]

    // intersection
    colors.intersection(&flag_colors); // ["red"]

    // union
    colors.union(&flag_colors); // ["red", "blue", "green", "black"]
}

or syntax sugared using maplit crate

#[macro_use] extern crate maplit;

let colors = hashset!{"red", "green", "blue", "blue"};

while and for loops

Looping until a condition is met or over an iterable object.

Python

# While loop

counter = 0
while counter < 10:
    print(counter)
    counter += 1

# infinite while loop
while True:
    print("loop Forever!")

# infinite ehile loop with break
counter = 0
while True:
    print(counter)
    counter += 1
    if counter >= 10:
        break


# while loop with continue
counter = 0
while True:
    counter += 1
    if counter == 5:
        continue
    print(counter)
    if counter >= 10:
        break

# For loop over a list
for color in ["red", "green", "blue"]:
    print(color)

# Enumerating indexes
for  i, color in enumerate(["red", "green", "blue"]):
    print(f"{color} at index {i}")

# For in a range
for number in range(0, 100):
    print(number)  # from 0 to 99

Rust

fn main() {

    // While loop
    let mut counter = 0;
    while counter < 10 {
        println!("{}", counter);
        counter += 1;
    }

    // infinite while loop
    loop {
        println!("Loop forever!");
    }

    // infinite while loop with break
    let mut counter = 0;
    loop {
        println!("{}", counter);
        counter += 1;
        if counter >= 10 { break; }
    }

    // infinite while loop with continue
    let mut counter = 0;
    loop {
        counter += 1;
        if counter == 5 { continue; }
        println!("{}", counter);
        if counter >= 10 { break; }
    }

    // for loop over a list
    for color in ["red", "green", "blue"].iter() {
        println!("{}", color);
    }

    // Enumerating indexes
    for (i, color) in ["red", "green", "blue"].iter().enumerate() {
        println!("{} at index {}", color, i);
    }

    // for in a range
    for number in 0..100 {
        println!("{}", number);  // from 0 to 99
    }
}

Loop Labels

Rust has a looping feature which is not present on Python: Loop labels

'outer: for x in 0..10 {
    'inner: for y in 0..10 {
        if x % 2 == 0 { continue 'outer; } // continues the loop over x
        if y % 2 == 0 { continue 'inner; } // continues the loop over y
        println!("x: {}, y: {}", x, y);
    }
}

Files

Read a text file and iterate its lines printing the content, properly close the file at the end.

Python

from pathlib import Path

with open(Path("/tmp/song.txt")) as fp:
    #  Iterate over lines
    for line in fp:
        print(line.strip())

Rust

use std::io::{BufReader, BufRead};
use std::fs::File;
use std::path::Path;


fn main () {
    let fp = File::open(Path::new("/tmp/song.txt")).unwrap();
    let file = BufReader::new(&fp);
    for line in file.lines() {
        //  Iterate over lines
        println!("{}", line.unwrap());
    }
}

Exceptions/Return Error

Expecting for exceptions and identifying errors.

Python

def div(a, b):
    if b == 0:
        raise ValueError("b can't be 0")
    return a / b

# ...

try:
    div(1, 0)
except ValueError:
    print('OK')

Rust

Concurrency

Python

thr = Thread(target=add, args=(1, 2), daemon=True)
thr.start()

Rust

Communicating between threads

Managing data context between threads.

Python

from queue import Queue
queue = Queue()
# ...
# Send message from a thread
queue.put(353)


# ...
# Get message to a thread
val = queue.get()

Rust

Sorting

Sorting lists, reversing and using a key.

Python

names = ['taz', 'bugs', 'daffy']

# Lexicographical order
names.sort()

# Reversed lexicographical order
names.sort(reverse=True)

# Sort by length
names.sort(key=len)

Rust

Web app with Flask / Rocket

Python

from flask import Flask

app = Flask(__name__)


@app.route('/')
def index():
    return 'Hello Python'


if __name__ == '__main__':
    app.run(port=8080)

Rust

#![feature(plugin)]
#![plugin(rocket_codegen)]

extern crate rocket;

#[get("/")]
fn index() -> &'static str {
    "Hello Rust"
}

fn main() {
    rocket::ignite().mount("/", routes![index]).launch();
}

HTTP Request with error handling

Python

import json
from urlib2 import urlopen

url = 'https://httpbin.org/ip'
try:
    fp = urlopen(url)
except HTTPError as err:
    msg = 'error: cannot get {!r} - {}'.format(url, err)
    raise SystemExit(msg)

try:
    reply = json.load(fp)
except ValueError as err:
    msg = 'error: cannot decode reply - {}'.format(err)
    raise SystemExit(msg)

print(reply['origin'])

Rust

Encode and Decode JSON

Python

data = '''{
    "name": "bugs",
    "age": 76
}'''
obj = json.loads(data)

json.dump(obj, stdout)

Rust

Object Orientation

Python

playground

class Cat:
    def __init__(self, name):
        self.name = name

    def greet(self, other):
        print("Meow {}, I'm {}".format(other, self.name))

# ...

grumy = Cat('Grumpy')
grumy.greet('Garfield')  # Meow Garfield, I'm Grumpy

Rust

playground

struct Cat {
    name: String
}

impl Cat {

    pub fn new<S>(name: S) -> Cat where S: Into<String> {
        Cat { name: name.into() }
    }
    
    pub fn greet<S: Into<String>>(&self, other:S) {
        println!("Meow {}, I'm {}", other.into(), self.name);
    }     
    
}

fn main() {
    let grumpy = Cat::new("Grumpy");
    grumpy.greet("Garfield");  // Meow Garfield, I'm Grumpy
}

NOTE: In Rust, it is best to avoid stringly types APIs so in the above example it would be better if we do let garfield = Cat::new("Garfield") and then make greet to accept an instance of Cat as other argument. If you are interested watch this.

Print Object for Debug/Log

Print formatted object debug information

Python

class Actor:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __repr__(self):
      return str(self.__dict__)

daffy = Actor(
    name='Daffy',
    age=80,
)

print('{!r}'.format(daffy))  # {'name': 'Daffy', 'age': 80}

Rust

#[derive(Debug)]
struct Actor {
    name: String,
    age: i32
}

fn main() {
    let daffy = Actor {name: "Daffy".into(), age: 80};
    println!("{:#?}", daffy);   // Actor {name: "Daffy", age: 80 }
}

Template for new examples

Explanation comes here.

Python

playground

# python code goes here

Rust

playground

// rust code goes here

Credits

Created by Bruno Rocha @rochacbruno inspired by https://www.353.solutions/py2go/index.html

First published in BrunoRocha.org

With contributions by:

• Send a PR and include your name and links