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https://github.com/kennethreitz/heroku-buildpack-python.git
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Ed Morley
405c7651ea
`get-pip.py` is no longer used, since: - It uses `--force-reinstall`, which is unnecessary here and slows down repeat builds (given we call pip install every time now). Trying to work around this by using `get-pip.py` only for the initial install, and real pip for subsequent updates would mean we lose protection against cached broken installs, plus significantly increase the version combinations test matrix. - It means downloading pip twice (once embedded in `get-pip.py`, and again during the install, since `get-pip.py` can't install the embedded version directly). - We would still have to manage several versions of `get-pip.py`, to support older Pythons (once we upgrade to newer pip). We don't use `ensurepip` since: - not all of the previously generated Python runtimes on S3 include it. - we would still have to upgrade pip/setuptools afterwards. - the versions of pip/setuptools bundled with ensurepip differ greatly depending on Python version, and we could easily start using a CLI flag for the first pip install before upgrade that isn't supported on all versions, without even knowing it (unless we test against hundreds of Python archives). Instead we install pip using itself in wheel form. See: https://github.com/pypa/pip/issues/2351#issuecomment-69994524 The new pip wheel assets on S3 were generated using: ``` $ pip download --no-cache pip==19.1.1 Collecting pip==19.1.1 Downloading pip-19.1.1-py2.py3-none-any.whl (1.4 MB) Saved ./pip-19.1.1-py2.py3-none-any.whl Successfully downloaded pip $ pip download --no-cache pip==20.0.2 Collecting pip==20.0.2 Downloading pip-20.0.2-py2.py3-none-any.whl (1.4 MB) Saved ./pip-20.0.2-py2.py3-none-any.whl Successfully downloaded pip $ aws s3 sync . s3://lang-python/common/ --exclude "*" --include "*.whl" --acl public-read --dryrun (dryrun) upload: ./pip-19.1.1-py2.py3-none-any.whl to s3://lang-python/common/pip-19.1.1-py2.py3-none-any.whl (dryrun) upload: ./pip-20.0.2-py2.py3-none-any.whl to s3://lang-python/common/pip-20.0.2-py2.py3-none-any.whl $ aws s3 sync . s3://lang-python/common/ --exclude "*" --include "*.whl" --acl public-read upload: ./pip-19.1.1-py2.py3-none-any.whl to s3://lang-python/common/pip-19.1.1-py2.py3-none-any.whl upload: ./pip-20.0.2-py2.py3-none-any.whl to s3://lang-python/common/pip-20.0.2-py2.py3-none-any.whl ```
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Python Buildpack Install Steps
TODO: Add context on Python install steps, such as why symlinking vs copying
Installing Python packages using Pip
Convention: Use python process to invoke Pip
We don't use this convention (yet) but this is an upcoming change being considered.
This is a bigger concern on Windows than it is in Linux environments, but an emerging convention in the Python community is to invoke pip using:
python3 -m pip [options]
Invoking pip this way ensures correct location - python knows where these packages are stored because it put them there (defaults to Python's pathing info).
All normal command line options are available using this method.