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');

External links

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Alternative Python implementations:
* Jython
* Transcrypt

Table Of Contents
2 Filter
3 List
7 Loops
22 Reduce
27 Classes
31 Set
42 Tuple
45 Enum
62 Sockets
89 urllib
92 Idioms
104 Stack
105 Profiling
109 Logging
111 os module
118 Mixins
120 ArcPy
126 Arrays
129 Alternative Python implementations
132 2to3 tool
135 Unicode
138 Neo4j
140 Curses
141 Templates
145 heapq
146 tkinter
154 Audio
155 pyglet
157 ijson
160 Flask
161 Groupby
163 pygame
165 hashlib
166 Gzip
167 ctypes
185 pyaudio
186 shelve