Transcrypt

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Transcrypt is a tool to precompile a fairly extensive subset of Python into compact, readable Javascript. It has the following characteristics:

Code size and speed

Experience has shown that 650 kB of Python sourcecode roughly translates in the same amount of JavaScript source code. The speed matches the speed of handwritten JavaScript and can surpass it if call memoizing is switched on.

Integration with HTML

<script src="__javascript__/hello.js"></script>
<h2>Hello demo</h2>

<p>
<div id = "greet">...</div>
<button onclick="hello.solarSystem.greet ()">Click me repeatedly!</button>

<p>
<div id = "explain">...</div>
<button onclick="hello.solarSystem.explain ()">And click me repeatedly too!</button>

Integration with JavaScript and DOM

from itertools import chain

class SolarSystem:
    planets = [list (chain (planet, (index + 1,))) for index, planet in enumerate ((
        ('Mercury', 'hot', 2240),
        ('Venus', 'sulphurous', 6052),
        ('Earth', 'fertile', 6378),
        ('Mars', 'reddish', 3397),
        ('Jupiter', 'stormy', 71492),
        ('Saturn', 'ringed', 60268),
        ('Uranus', 'cold', 25559),
        ('Neptune', 'very cold', 24766) 
    ))]
    
    lines = (
        '{} is a {} planet',
        'The radius of {} is {} km',
        '{} is planet nr. {} counting from the sun'
    )
    
    def __init__ (self):
        self.lineIndex = 0
    
    def greet (self):
        self.planet = self.planets [int (Math.random () * len (self.planets))]
        document.getElementById ('greet') .innerHTML = 'Hello {}'.format (self.planet [0])
        self.explain ()
        
    def explain (self):
        document.getElementById ('explain').innerHTML = (
            self.lines [self.lineIndex] .format (self.planet [0], self.planet [self.lineIndex + 1])
        )
        self.lineIndex = (self.lineIndex + 1) % 3
         solarSystem = SolarSystem ()

Integration with other JavaScript libraries

Transcrypt can be used in combination with any JavaScript library without special measures or syntax. In the documentation examples are given for a.o. react.js, riot.js, fabric.js and node.js.

Relation between Python and JavaScript code

Python

class A:
    def __init__ (self, x):
        self.x = x

    def show (self, label):
        print ('A.show', label, self.x)
    
class B:
    def __init__ (self, y):
        alert ('In B constructor')
        self.y = y
        
    def show (self, label):
        print ('B.show', label, self.y)
        
class C (A, B):
    def __init__ (self, x, y):
        alert ('In C constructor')
        A.__init__ (self, x)
        B.__init__ (self, y)
        self.show ('constructor')
        
    def show (self, label):
        B.show (self, label)
        print ('C.show', label, self.x, self.y)
    
a = A (1001)
a.show ('america')

b = B (2002)
b.show ('russia')

c = C (3003, 4004)
c.show ('netherlands')

show2 = c.show
show2 ('copy')

JavaScript

var A = __class__ ('A', [object], {
    get __init__ () {return __get__ (this, function (self, x) {
        self.x = x;
    });},
    get show () {return __get__ (this, function (self, label) {
        print ('A.show', label, self.x);
    });}
});
var B = __class__ ('B', [object], {
    get __init__ () {return __get__ (this, function (self, y) {
        alert ('In B constructor');
        self.y = y;
    });},
    get show () {return __get__ (this, function (self, label) {
        print ('B.show', label, self.y);
    });}
});
var C = __class__ ('C', [A, B], {
    get __init__ () {return __get__ (this, function (self, x, y) {
        alert ('In C constructor');
        A.__init__ (self, x);
        B.__init__ (self, y);
        self.show ('constructor');
    });},
    get show () {return __get__ (this, function (self, label) {
        B.show (self, label);
        print ('C.show', label, self.x, self.y);
    });}
});
var a = A (1001);
a.show ('america');
var b = B (2002);
b.show ('russia');
var c = C (3003, 4004);
c.show ('netherlands');
var show2 = c.show;
show2 ('copy');

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