Kyle Conroy

Proposed Python Standard Library Removals Will Break 1 in 30 PyPI Packages

PEP 594 outlines the plan to deprecate and remove packages from the Python standard library. If accepted in its current form, PEP 594 will break 3.8% of all Python 3 packages on PyPI.

As of May 2019 there are 3,604 Python 3 packages on PyPI (out of 94,680) that import packages deprecated by PEP 594.

  total packages: 181225
  valid packages: 178642
python3 packages: 94680
scanned packages: 92779
 broken packages: 3604

The majority of these packages import the parser or imp package. If those two packages were removed from PEP 594, the number of broken packages drops to 828.

Is 3,600 broken packages enough to block adoption of the PEP? I don't know. I just wanted to make sure that the impact the PEP was known before a final decision.

Reproduce the Results

Before you begin, you'll need Python >= 3.6 and a recent version of Go to run the code. All commands should be run inside a cloned checkout of the dead-batteries repository. First, build the binary.

git clone https://github.com/kyleconroy/dead-batteries.git
cd dead-batteries
go build

Next, you'll download the metadata for every package on PyPI, which will take up about ~500MB of space.

./dead-battery mirror
  • simple.html: contains a list of all known packages on PyPI
  • meta/*.json: contains package metadata for each package
  • python3-packages.json: contains a list of packages that support Python3

With a complete mirror, you're now ready to scan packages for imports of deprecated packages. Open up a new shell to install and run the Python service.

python3 -m venv venv
venv/bin/pip install flask
venv/bin/pip install gunicorn
venv/bin/pip install gunicorn[gevent]
venv/bin/gunicorn -k gevent -w 10 -b 127.0.0.1:4000 imports:app

The service exposes a HTTP/JSON interface to the ast package. It parses a given file and returns any deprecated imports as well as parsing errors.

// INPUT
{
  "path": "/path/to/python/file"
}

// OUTPUT
{ 
  "imports": {
    "imp": 2
  },
  "errors": {
    "syntax-error": 2
  }
}

With that running, you can now start the scan. On my laptop, the scan took about an hour to complete. The output is continually saved to results.json.

./dead-battery scan

Once the search process is complete, generate the package statistics.

./dead-battery stats

Two new files have been created: import.csv and packages.json. The CSV file contains the total number of imports for each deprecated standard library package. The JSON file contains a list of every package that imports one of these deprecated packages, along with a link to the package on PyPI.

A quick jump into the Python interpreter gives us the total number of packages affected by PEP 594.

>>> import json
>>> len(json.load(open('packages.json')))
3604

Methodology

Since PEP 594 only affects Python 3, I needed to filter out packages that don't support Python 3. For each package, I first looked for any classifiers with the prefix Programming Language :: Python :: 3. Next, I checked the python_version of the latest release. It's a bit messy, but the code to do so can be found here.

{
    "info": {
        "classifiers": [
            "Programming Language :: Python :: 2.7",
            "Programming Language :: Python :: 3"
        ],
        "version": "2.22.0"
    },
    "releases": {
        "2.22.0": [
            {
                "packagetype": "bdist_wheel",
                "python_version": "py2.py3",
                "url": "https://files.pythonhosted.org/.../requests-2.22.0-py2.py3-none-any.whl"
            }
        ]
    }
}

If you know a better way to check for Python 3 compatibility, please reach out