Minify Python 2 source code

## Project description

a Python 2 minifier by Gareth Rees <http://garethrees.org/>

## Introduction

minipy is a minifier for Python 2. It rewrites Python 2 source code in a way that preserves the meaning of the code while reducing it in size. For example:

$cat fib.py cache = {0: 0, 1: 1, 2: 1, 3: 2} def fibonacci(n): """Return the nth Fibonacci number.""" if n not in cache: a = n // 2 r = n % 2 m = (r * 2) - 1 cache[n] = fibonacci(a + 1) ** 2 + m * fibonacci(a + r - 1) ** 2 return cache[n]$ minipy --rename --docstrings fib.py
b={0:0,1:1,2:1,3:2}
def c(a):
if a not in b:d=a//2;e=a%2;f=e*2-1;b[a]=c(d+1)**2+f*c(d+e-1)**2
return b[a]


## Command line

Usage: minipy [options] [-o OUTPUT] FILE

Options:
--version             show program's version number and exit
-h, --help            show this help message and exit
-o OUTPUT, --output=OUTPUT
output file (default: stdout)
-D, --docstrings      remove docstrings and other statements with no side
effects (implies --noselftest)
-R, --rename          aggressively rename non-preserved variables
-i INDENT, --indent=INDENT
number of spaces per indentation level
-p PRESERVE, --preserve=PRESERVE
preserve words from renaming (separate by commas)
--nojoinlines         put each statement on its own line
--noselftest          skip the self-test
--debug               dump the parse tree


## The self-test

Generating minified source code without accidentally changing the meaning is tricky: see the list of issues for many awkward cases that had to be fixed. Therefore, in its default operating mode, minipy performs a “self-test”: it takes the minified code, re-parses it, and asserts that the parse tree for the minified code is identical to the parse tree for the original code. If the self-test passes, then you can be highly confident that minipy has not changed the meaning of your code.

In order to pass the self-test, minipy must eschew a few changes to the code that result in harmless changes to the parse tree. These changes are:

• Replacing pass with 0.
• Replacing -(1) with -1.

You can use the --noselftest option to enable these changes, but by disabling the self-test you accept a small risk of a bug in minipy changing the meaning of your code.

The optional transformations --rename and --docstrings can’t be combined with the self-test, so these options imply --noselftest.

Please report all self-test failures, attaching the code that causes the failure.

## Renaming

Python’s use of introspection and duck typing means that it is not possible to change names in a program without risk of changing the meaning. The --rename option to minipy therefore makes a “best attempt” to discover names that need to be preserved, but does not guarantee anything. Use at your own risk!

The following names are preserved when renaming:

• Names specified on the command-line via the --preserve option (write --preserve=name1,name2,name3 to preserve more than one name).
• Built-in names (abs, all, any, apply, …).
• Any name used as an attribute (.join, .index, .copy, .sort, …).
• Any name starting and ending with two underscores.
• The names of all imported modules.
• Any name exported by a module in a from module import * statement.
• Any name in the list assigned to the __all__ global variable.