Example direnv .envrc for Python projects that manages a local virtualenv that updates automatically when requirements.txt changes

.envrc

#!/bin/bash
set -euo pipefail

VIRTUAL_ENV=".venv"
REQUIREMENTS_HASH_FILE="$VIRTUAL_ENV/requirements.shasum"
REQUIREMENTS_HASH_FUNC="shasum"
REQUIREMENTS_HASH_VAL=$($REQUIREMENTS_HASH_FUNC requirements.txt | cut -d ' ' -f 1)

function reset_venv() {
    if ! has uv; then
        echo 'error: `uv` command not found. install with `brew install uv`'
        exit 1
    fi

    rm -rf "$VIRTUAL_ENV"
    uv venv
    uv pip install -r requirements.txt
    printf '%s' "$REQUIREMENTS_HASH_VAL" >"$REQUIREMENTS_HASH_FILE"
}

if [ ! -f "$REQUIREMENTS_HASH_FILE" ]; then
    echo "setting up new python virtualenv in $VIRTUAL_ENV ..."
    reset_venv
elif [ "$(cat $REQUIREMENTS_HASH_FILE)" != "$REQUIREMENTS_HASH_VAL" ]; then
    echo "python requirements changed, rebuilding virtualenv in $VIRTUAL_ENV ..."
    echo "(found hash $(cat $REQUIREMENTS_HASH_FILE), want hash $REQUIREMENTS_HASH_VAL)"
    reset_venv
fi

PATH_add "$VIRTUAL_ENV/bin"