ccextractor/vardbg

A simple Python debugger and profiler that generates animated visualizations of program flow, useful for algorithm learning.

vardbg

A simple Python debugger and profiler that generates animated visualizations of program flow. It is meant to help with learning algorithms by allowing you to visualize what the algorithms are doing.

Python 3.6 or newer is required due to the use of f-strings.

This project was created during Google Code-in 2019 for CCExtractor Development.

Demo

Features

• Tracking the history of each variable and its contents
• Tracking elements within containers (lists, sets, dicts, etc.)
• Ignoring specific variables
• Profiling the execution of each line
• Summarizing all variables and execution times after execution
• Passing arguments to debugged programs
• Exporting execution history in JSON format and replaying (including program output)
• Creating videos that show program flow, execution times, variables (with relationships), and output
• Writing videos in MP4, GIF, and WebP formats

Installation

The latest tagged version can be obtained from PyPI:

pip install vardbg

Alternatively, one can clone this repository and run it directly after installing dependencies:

git clone https://github.com/CCExtractor/vardbg
cd vardbg
python3 -m venv venv
source venv/bin/activate
pip install poetry
poetry install .
./debug.py

It can also be installed from the repository:

pip install .

The above instructions assume the use of a virtual environment to avoid interfering with the system install of Python.

Usage

All of the debugger's subcommands and options are documented in the usage help, which is readily available on the command line.

For example, this command will debug the function quick_sort from the file sort.py with the arguments 9 3 5 1 and record the session to a JSON file named sort1.json:

vardbg run sort.py quick_sort -o qsort.json -a 9 -a 3 -a 5 -a 1

A video can then be generated from the above recording:

vardbg replay qsort.json -v sort_vis.mp4

It is possible to generate videos live while running the debugged program, but this is discouraged because the overhead of video creation inflates execution times greatly and thus ruins profiler results. However, if profiling is not important to you, it is a valid use case.

Configuration

The video generator has many options: resolution, speed, fonts, and sizes. These options can be modified using a TOML config file. The default config documents the available options, which can be customized in an minimal overlay config without having to duplicate the entire config. The config can then be used by passing the -c argument on the command line.

An example of a simple overlay is the config used to generate official demo videos for embedding in READMEs. This simple config increases the speed (FPS) slightly and adds an intro screen at the beginning of the video.

Behavior Control

Special comments can be added to lines of code that define variables to control how vardbg handles said variable:

• # vardbg: ignore — do not display this variable or track its values
• # vardbg: ref lst[i] — treat variable i as the index/key of an element in container lst (only shown in videos)

Specifying the name of the variable may appear to be redundant, but there are two reasons behind this: reliably parsing all code that defines variables is very hard (there are more possible methods than one might think — loops, unpacking, direct assignments, exec calls, etc.), and more than one variable can be declared on a line. For example, tuple unpacking and function arguments are common occurrences of multiple variables being added on a single line. Thus, specifying the variable name in references is mandatory to prevent ambiguity.

Contributing

Feel free to contribute to this project! You can add features, fix bugs, or make any other improvements you see fit. We just ask that you follow the code style guidelines to keep the code consistent and coherent. These guidelines can easily be enforced before pushing with the pre-commit framework, which can install Git pre-commit hooks with the pre-commit install command.

Once your contribution meets the guidelines, open a pull request to make things official.

vardbg's Issues

`time_ns` not in Python 3.6

The main README says that Python 3.6 or later is required, but the code requires time.time_ns(). AFAIK this was introduced in 3.7.

Dependabot couldn't authenticate with https://pypi.python.org/simple/

Dependabot couldn't authenticate with https://pypi.python.org/simple/.

You can provide authentication details in your Dependabot dashboard by clicking into the account menu (in the top right) and selecting 'Config variables'.

View the update logs.

ocr

i get the error messge ####parameter ocr not understood#### my pc is a gpu windows 10 professional. is this a bug?
thanks for all the hard work you are putting into this project

james raftree

how to run this interesting project

hi, I want to know how can I type correct comman to get video
I run the (debug.py) with terminal

No time.time_ns() in python 3.6

Hello,
In ReadMe you say that Python 3.6 or newer is required to launch vardbg, but it makes use of time_ns() function in the time module, which was introduced in Python 3.7

Thank you for this nice project.

The executing line highlighting should animate the scroll to line

It's jarring and confusing, particularly when the next line is many lines away from the current line.

For example, in the animation in the README, when it scrolls to the insertion_sort function implementation, it's not immediately clear what happened.

A possibly better implementation would have some sort of animation showing the scroll to that point and the movement of the highlight to that point.

Add support for custom color themes

Dependabot can't resolve your Python dependency files

Dependabot can't resolve your Python dependency files.

As a result, Dependabot couldn't update your dependencies.

The error Dependabot encountered was:

Creating virtualenv vardbg-mx-TPUc0-py3.8 in /home/dependabot/.cache/pypoetry/virtualenvs
Updating dependencies
Resolving dependencies...

[PackageNotFound]
Package sortedcontainers (2.1.0) not found.

If you think the above is an error on Dependabot's side please don't hesitate to get in touch - we'll do whatever we can to fix it.

View the update logs.