python

Recovering lost Python source code if it’s still resident in-memory

I read this on GitHub Gist the other day. I don’t know whether I will ever use it but I am still putting this on my blog for the sake of bookmarking it. Who knows? Someone from the audience might end up using it!

I screwed up using git (“git checkout –” on the wrong file) and managed to delete the code I had just written… but it was still running in a process in a docker container. Here’s how I got it back, using https://pypi.python.org/pypi/pyrasite/ and https://pypi.python.org/pypi/uncompyle6

Attach a shell to the docker container


Install GDB (needed by pyrasite)

apt-get update && apt-get install gdb

Install pyrasite – this will let you attach a Python shell to the still-running process

pip install pyrasite

Install uncompyle6, which will let you get Python source code back from in-memory code objects

pip install uncompyle6

Find the PID of the process that is still running

ps aux | grep python

Attach an interactive prompt using pyrasite

pyrasite-shell <PID>

Now you’re in an interactive prompt! Import the code you need to recover

>>> from my_package import my_module

Figure out which functions and classes you need to recover

>>> dir(my_module)
['MyClass', 'my_function']

Decompile the function into source code

>>> import uncompyle6
>>> import sys
>>> uncompyle6.main.uncompyle(
    2.7, my_module.my_function.func_code, sys.stdout
)
# uncompyle6 version 2.9.10
# Python bytecode 2.7
# Decompiled from: Python 2.7.12 (default, Nov 19 2016, 06:48:10) 
# [GCC 5.4.0 20160609]
# Embedded file name: /srv/my_package/my_module.py
function_body = "appears here"

For the class, you’ll need to decompile each method in turn

>>> uncompyle6.main.uncompyle(
    2.7, my_module.MyClass.my_method.im_func.func_code, sys.stdout
)
# uncompyle6 version 2.9.10
# Python bytecode 2.7
# Decompiled from: Python 2.7.12 (default, Nov 19 2016, 06:48:10) 
# [GCC 5.4.0 20160609]
# Embedded file name: /srv/my_package/my_module.py
class_method_body = "appears here"

I hope you guys like this post. Stay tuned for the next one in the upcoming days.

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One thought on “Recovering lost Python source code if it’s still resident in-memory

  1. phihag says:

    If you are using a good editor, that editor will also record states before the checkout (some even ask you which version you want). Try pressing Ctrl+Z multiple times. And don’t forget to commit regularly!

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