pip freeze

-r, --requirement <file>    Install from the given requirements file. This option can be used multiple times.

-c, --constraint <file>     Constrain versions using the given constraints file. This option can be used multiple times.

#!/usr/bin/env bash
# <https://www.pantsbuild.org/docs/python-third-party-dependencies#tip-set-up-a-virtual-environment-optional>
# this script was modified to use `virtualenv` instead of `venv`
# this script was modified to check if `jq` is installed
set -euo pipefail
set -x

if ! command -v jq &> /dev/null
then
    echo "jq could not be found"
    exit
fi

# You can change these constants.
PYTHON_BIN=python3
VIRTUALENV=build-support/.venv
REQUIREMENTS_FILE=requirements.txt
CONSTRAINTS_FILE=constraints.txt

"${PYTHON_BIN}" -m virtualenv --version || "${PYTHON_BIN}" -m pip install virtualenv
"${PYTHON_BIN}" -m virtualenv "${VIRTUALENV}"
. "${VIRTUALENV}"/bin/activate
pip install --upgrade pip

# Install all our requirements.txt, and also any 3rdparty
# dependencies specified outside requirements.txt, e.g. via a
# handwritten python_requirement_library target.
pip install \
  -r "${REQUIREMENTS_FILE}" \
  -r <(./pants dependencies :: |
    xargs ./pants filter --target-type=python_requirement |
    xargs ./pants peek |
    jq -r '.[]["requirements"][]')
echo "# Generated by build-support/generate_constraints.sh on $(date)" > "${CONSTRAINTS_FILE}"
pip freeze --all >> "${CONSTRAINTS_FILE}"