🐍➡️ FakePy Transpiler

A Python-to-JavaScript transpiler written in Node.js. It converts a subset of Python syntax into runnable JavaScript, executing it directly in the terminal.

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📋 Table of Contents

• Overview
• Features
• Project Structure
• How It Works
• Getting Started
• Supported Syntax
• Examples
• Running Tests
• Limitations

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Overview

FakePy Transpiler takes Python source code (written in fakepy.txt), tokenizes it, parses it into an AST, and generates equivalent JavaScript code that is then executed at runtime. It supports a meaningful subset of Python including variables, control flow, functions, lists, and more.

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✨ Features

• ✅ Variables (assignment and reassignment)
• ✅ Arithmetic and comparison operators
• ✅ print() with optional end= argument
• ✅ input() with async support
• ✅ if / else conditionals
• ✅ for loops with range() (start, stop, step)
• ✅ while loops
• ✅ break and continue
• ✅ Function definitions (def) and calls
• ✅ return statements
• ✅ Lists with index access
• ✅ List methods: append, pop, reverse, sort, index, copy, extend, insert, remove, count
• ✅ Built-ins: len(), int(), float(), str()
• ✅ Boolean literals: True / False
• ✅ Logical operators: and, or
• ✅ String concatenation via +
• ✅ Comments with #

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📁 Project Structure

transpiler/
│
├── index.js        # Entry point — CLI interface, runs txt file or test suite
├── lexer.js        # Tokenizer — converts raw source code into a token list
├── parser.js       # Parser — builds an AST from the token list
├── ast.js          # AST node class definitions
├── codegen.js      # Code generator — converts AST into JavaScript source
├── runetime.js     # Runtime helper — executes generated JS via eval
├── tests.js        # Test cases and expected outputs
├── fakepy.txt      # Sample Python-like source file to transpile and run
└── package.json    # Project metadata (ES modules)

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⚙️ How It Works

The transpiler follows the classic compiler pipeline:

Source Code (fakepy.txt)
        │
        ▼
   [ Lexer ]          → Tokenizes the raw text into a stream of tokens
        │
        ▼
   [ Parser ]         → Builds an Abstract Syntax Tree (AST)
        │
        ▼
  [ Code Generator ]  → Traverses the AST and emits JavaScript code
        │
        ▼
   [ Runtime ]        → Executes the generated JS using eval()

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🚀 Getting Started

Prerequisites

• Node.js v16 or higher (ES modules support required)

Installation

git clone https://github.com/your-username/fakepy-transpiler.git
cd fakepy-transpiler

No dependencies to install — the project uses only Node.js built-ins.

Run

node index.js

You'll be prompted to choose between:

1. Run fakepy.txt — transpiles and executes the sample Python file
2. Run tests — runs the built-in test suite and shows pass/fail results

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📝 Supported Syntax

Variables

x = 10
name = "Filippo"
x += 5

Conditionals

if x > 5:
    print("grande")
else:
    print("piccolo")

Loops

for i in range(10):
    print(i)

for i in range(0, 10, 2):
    print(i)

while x > 0:
    x -= 1

Functions

def somma(a, b):
    return a + b

risultato = somma(3, 7)
print(risultato)

Lists

a = [1, 2, 3]
a.append(4)
a.reverse()
print(a[0])
print(len(a))

Input

nome = input("Come ti chiami? ")
print(nome)

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🧪 Running Tests

When you launch the program and select option 2, it runs 16 automated tests covering:

• Function definitions and calls
• Nested functions
• List manipulation
• Loops and conditionals
• Return values
• List methods (append, pop, reverse, sort, index, copy)

Results are printed as ✅ (pass) or ❌ (fail) with expected vs actual output.

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⚠️ Limitations

• Only for i in range(...) loops are supported — no for x in list iteration
• No classes or object-oriented features
• No elif chains (only if / else)
• No multi-line strings or f-strings
• No exception handling (try / except)
• Indentation must use spaces (tabs not supported)
• No module imports within the fake Python source

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👤 Author

Filippo Chiarolla