Support running with the Windows embeddable Python distribution

docs/changelog.md

@@ -19,6 +19,7 @@ dev
 - [bugfix] Requiring userpath v1.4.1 or later so ensure Windows bug is fixed for `ensurepath` (#437)
 - [feature] log pipx version (#423)
 - [feature] `--suffix` option for `install` to allow multiple versions of same tool to be installed (#445)
+- [feature] pipx can now be used with the Windows embeddable Python distribution
 
 0.15.4.0
 

src/pipx/constants.py

@@ -3,7 +3,6 @@
 from pathlib import Path
 from textwrap import dedent
 
-DEFAULT_PYTHON = sys.executable
 DEFAULT_PIPX_HOME = Path.home() / ".local/pipx"
 DEFAULT_PIPX_BIN_DIR = Path.home() / ".local/bin"
 PIPX_HOME = Path(os.environ.get("PIPX_HOME", DEFAULT_PIPX_HOME)).resolve()

src/pipx/interpreter.py

@@ -0,0 +1,60 @@
+import shutil
+import subprocess
+import sys
+
+from pipx.constants import WINDOWS
+from pipx.util import PipxError
+
+
+def has_venv() -> bool:
+    try:
+        import venv  # noqa
+
+        return True
+    except ImportError:
+        return False
+
+
+# If we are running under the Windows embeddable distribution,
+# venv isn't available (and we probably don't want to use the
+# embeddable distribution as our applications' base Python anyway)
+# so we try to locate the system Python and use that instead.
+
+# This code was copied from https://github.com/uranusjr/pipx-standalone
+# which uses this technique to build a completely standalone pipx
+# distribution
+
+
+def _find_default_windows_python() -> str:
+
+    if has_venv():
+        return sys.executable
+
+    py = shutil.which("py")
+    if py:
+        return py
+    python = shutil.which("python")
+    if python is None:
+        raise PipxError("no suitable Python found")
+
+    if "WindowsApps" not in python:
+        return python
+    # Special treatment to detect Windows Store stub.
+    # https://twitter.com/zooba/status/1212454929379581952
+
+    proc = subprocess.run(
+        [python, "-V"], stdout=subprocess.PIPE, stderr=subprocess.DEVNULL,
+    )
+    if proc.returncode != 0:
+        # Cover the 9009 return code pre-emptively.
+        raise PipxError("no suitable Python found")
+    if not proc.stdout.strip():
+        # A real Python should print version, Windows Store stub won't.
+        raise PipxError("no suitable Python found")
+    return python  # This executable seems to work.
+
+
+if WINDOWS:
+    DEFAULT_PYTHON = _find_default_windows_python()
+else:
+    DEFAULT_PYTHON = sys.executable

src/pipx/main.py

@@ -17,6 +17,7 @@
 from . import commands, constants
 from .animate import hide_cursor, show_cursor
 from .colors import bold, green
+from .interpreter import DEFAULT_PYTHON
 from .util import PipxError, mkdir
 from .venv import VenvContainer
 from .version import __version__
@@ -266,7 +267,7 @@ def _add_install(subparsers):
     )
     p.add_argument(
         "--python",
-        default=constants.DEFAULT_PYTHON,
+        default=DEFAULT_PYTHON,
         help=(
             "The Python executable used to create the Virtual Environment and run the "
             "associated app/apps. Must be v3.5+."
@@ -379,7 +380,7 @@ def _add_reinstall_all(subparsers):
     )
     p.add_argument(
         "--python",
-        default=constants.DEFAULT_PYTHON,
+        default=DEFAULT_PYTHON,
         help=(
             "The Python executable used to recreate the Virtual Environment "
             "and run the associated app/apps. Must be v3.5+."
@@ -448,7 +449,7 @@ def _add_run(subparsers):
     p.add_argument("--verbose", action="store_true")
     p.add_argument(
         "--python",
-        default=constants.DEFAULT_PYTHON,
+        default=DEFAULT_PYTHON,
         help="The Python version to run package's CLI app with. Must be v3.5+.",
     )
     add_pip_venv_args(p)

src/pipx/shared_libs.py

@@ -5,7 +5,8 @@
 import datetime
 
 from pipx.animate import animate
-from pipx.constants import DEFAULT_PYTHON, PIPX_SHARED_LIBS, WINDOWS
+from pipx.constants import PIPX_SHARED_LIBS, WINDOWS
+from pipx.interpreter import DEFAULT_PYTHON
 from pipx.util import get_site_packages, get_venv_paths, run
 
 SHARED_LIBS_MAX_AGE_SEC = datetime.timedelta(days=30).total_seconds()

src/pipx/venv.py

@@ -5,7 +5,8 @@
 from typing import Dict, Generator, List, NamedTuple, Set
 
 from pipx.animate import animate
-from pipx.constants import DEFAULT_PYTHON, PIPX_SHARED_PTH
+from pipx.constants import PIPX_SHARED_PTH
+from pipx.interpreter import DEFAULT_PYTHON
 from pipx.package_specifier import (
     parse_specifier_for_install,
     parse_specifier_for_metadata,

tests/test_interpreter.py

@@ -0,0 +1,81 @@
+import shutil
+import subprocess
+import sys
+import pytest  # type: ignore
+import pipx.interpreter
+from pipx.interpreter import _find_default_windows_python
+from pipx.util import PipxError
+
+
+def test_windows_python_venv_present(monkeypatch):
+    monkeypatch.setattr(pipx.interpreter, "has_venv", lambda: True)
+    assert _find_default_windows_python() == sys.executable
+
+
+def test_windows_python_no_venv_py_present(monkeypatch):
+    def which(name):
+        if name == "py":
+            return "py"
+
+    monkeypatch.setattr(pipx.interpreter, "has_venv", lambda: False)
+    monkeypatch.setattr(shutil, "which", which)
+    assert _find_default_windows_python() == "py"
+
+
+def test_windows_python_no_venv_python_present(monkeypatch):
+    def which(name):
+        if name == "python":
+            return "python"
+        # Note: returns False for "py"
+
+    monkeypatch.setattr(pipx.interpreter, "has_venv", lambda: False)
+    monkeypatch.setattr(shutil, "which", which)
+    assert _find_default_windows_python() == "python"
+
+
+def test_windows_python_no_venv_no_python(monkeypatch):
+    def which(name):
+        return None
+
+    monkeypatch.setattr(pipx.interpreter, "has_venv", lambda: False)
+    monkeypatch.setattr(shutil, "which", which)
+    with pytest.raises(PipxError):
+        _find_default_windows_python()
+
+
+# Test the checks for the store Python.
+def test_windows_python_no_venv_store_python(monkeypatch):
+    def which(name):
+        if name == "python":
+            return "WindowsApps"
+
+    class dummy_runner:
+        def __init__(self, rc, out):
+            self.rc = rc
+            self.out = out
+
+        def __call__(self, *args, **kw):
+            class Ret:
+                pass
+
+            ret = Ret()
+            ret.returncode = self.rc
+            ret.stdout = self.out
+            return ret
+
+    monkeypatch.setattr(pipx.interpreter, "has_venv", lambda: False)
+    monkeypatch.setattr(shutil, "which", which)
+
+    # Store version stub gives return code 9009
+    monkeypatch.setattr(subprocess, "run", dummy_runner(9009, ""))
+    with pytest.raises(PipxError):
+        _find_default_windows_python()
+
+    # Even if it doesn't, it returns no output
+    monkeypatch.setattr(subprocess, "run", dummy_runner(0, ""))
+    with pytest.raises(PipxError):
+        _find_default_windows_python()
+
+    # If it *does* pass the tests, we use it as it's not the stub
+    monkeypatch.setattr(subprocess, "run", dummy_runner(0, "3.8"))
+    assert _find_default_windows_python() == "WindowsApps"