pip_python_consistency.py

import sys
import os
import os.path
import subprocess
import json

# entry point for 'python -m pip'
def python_m_pip_main():
    do_pip(sys.argv)

# entry point for 'pip ...'
def pip_main():
    check_pip_python_consistency()
    do_pip(sys.argv)

# assumes POSIX for now
# needs to do something else on windows, but I don't know what :-)
def check_pip_python_consistency():
    pip_path = sys.argv[0]
    dirname, basename = os.path.split(pip_path)
    if not basename.startswith("pip"):
        # WTF?
        # I guess we continue and hope for the best...
        return
    python_basename = "python" + basename[len("pip"):]
    python_path = os.path.join(dirname, python_basename)
    # There's no reliable way to map from python executable path to environment
    # except by running it. This also lets us skip trying to implement our own
    # $PATH lookup...
    try:
        # mumble mumble do something about str/bytes here
        result = subprocess.check_output(
            [python_path, "-c", "import sys, json; json.dump([sys.prefix, sys.exec_prefix], sys.stdout)"])
    except subprocess.CalledProcessError:
        # Something is horribly wrong
        # But we have no idea what, so I guess we continue and hope for the best?
        return
    if json.loads(result) != [sys.prefix, sys.exec_prefix]:
        sys.stderr.write(
            "Mismatch detected between 'pip' and 'python' commands.\n"
            "This usually indicates some sort of installation problem.\n"
            "You ran:\n"
            "   {pip_path}\n"
            "which executed using the python interpreter at:\n"
            "   {pip_python_path}\n"
            "and we found a *different* python interpreter at:\n"
            "   {python_path}\n"
            "If you wanted to manage the {python_path} environment, try running:\n"
            "   {python_path} -m pip <arguments>\n"
            "If you really did want to manage the {pip_python_path} environment,\n"
            "adding --force-no-interpreter-check to your command-line will disable\n"
            "this check.\n"
            .format(pip_path=pip_path,
                    pip_python_path=sys.executable,
                    python_path=python_path))
            sys.exit(1)