Merge pull request #150 from ClementPinard/master

Add `--python` option

README.md

@@ -11,6 +11,7 @@ Dump the software license list of Python packages installed with pip.
 * [Usage](#usage)
 * [Command\-Line Options](#command-line-options)
     * [Common options](#common-options)
+        * [Option: python](#option-python)
         * [Option: from](#option-from)
         * [Option: order](#option-order)
         * [Option: format](#option-format)
@@ -97,6 +98,21 @@ Execute the command with your venv (or virtualenv) environment.
 
 ### Common options
 
+#### Option: python
+
+By default, this tools finds the packages from the environment pip-licenses is launched from, by searching in current python's `sys.path` folders. In the case you want to search for packages in an other environment (e.g. if you want to run pip-licenses from its own isolated environment), you can specify a path to a python executable. The packages will be searched for in the given python's `sys.path`, free of pip-licenses dependencies.
+
+```bash
+(venv) $ pip-licenses --with-system | grep pip
+ pip                       22.3.1       MIT License
+ pip-licenses              4.1.0        MIT License
+```
+
+```bash
+(venv) $ pip-licenses --python=</path/to/other/env>/bin/python --with-system | grep pip
+ pip                       23.0.1       MIT License 
+```
+
 #### Option: from
 
 By default, this tool finds the license from [Trove Classifiers](https://pypi.org/classifiers/) or package Metadata. Some Python packages declare their license only in Trove Classifiers.

piplicenses.py

@@ -30,7 +30,9 @@
 
 import argparse
 import codecs
+import os
 import re
+import subprocess
 import sys
 from collections import Counter
 from enum import Enum, auto
@@ -194,7 +196,21 @@ def filter_string(item: str) -> str:
 
         return pkg_info
 
-    pkgs = importlib_metadata.distributions()
+    def get_python_sys_path(executable: str) -> list[str]:
+        script = "import sys; print(' '.join(filter(bool, sys.path)))"
+        output = subprocess.run(
+            [executable, "-c", script],
+            capture_output=True,
+            env={**os.environ, "PYTHONPATH": "", "VIRTUAL_ENV": ""},
+        )
+        return output.stdout.decode().strip().split()
+
+    if args.python == sys.executable:
+        search_paths = sys.path
+    else:
+        search_paths = get_python_sys_path(args.python)
+
+    pkgs = importlib_metadata.distributions(path=search_paths)
     ignore_pkgs_as_lower = [pkg.lower() for pkg in args.ignore_packages]
     pkgs_as_lower = [pkg.lower() for pkg in args.packages]
 
@@ -785,6 +801,17 @@ def create_parser() -> CompatibleArgumentParser:
         "-v", "--version", action="version", version="%(prog)s " + __version__
     )
 
+    common_options.add_argument(
+        "--python",
+        type=str,
+        default=sys.executable,
+        metavar="PYTHON_EXEC",
+        help="R| path to python executable to search distributions from\n"
+        "Package will be searched in the selected python's sys.path\n"
+        "By default, will search packages for current env executable\n"
+        "(default: sys.executable)",
+    )
+
     common_options.add_argument(
         "--from",
         dest="from_",

test_piplicenses.py

@@ -4,11 +4,14 @@
 
 import copy
 import email
+import json
 import re
 import sys
 import unittest
+import venv
 from enum import Enum, auto
 from importlib.metadata import Distribution
+from types import SimpleNamespace
 from typing import TYPE_CHECKING, Any, List
 
 import docutils.frontend
@@ -39,6 +42,7 @@
     factory_styled_table_with_args,
     find_license_from_classifier,
     get_output_fields,
+    get_packages,
     get_sortby,
     output_colored,
     save_if_needs,
@@ -780,6 +784,26 @@ def test_allow_only(monkeypatch) -> None:
     )
 
 
+def test_different_python() -> None:
+    import tempfile
+
+    class TempEnvBuild(venv.EnvBuilder):
+        def post_setup(self, context: SimpleNamespace) -> None:
+            self.context = context
+
+    with tempfile.TemporaryDirectory() as target_dir_path:
+        venv_builder = TempEnvBuild(with_pip=True)
+        venv_builder.create(str(target_dir_path))
+        python_exec = venv_builder.context.env_exe
+        python_arg = f"--python={python_exec}"
+        args = create_parser().parse_args([python_arg, "-s", "-f=json"])
+        pkgs = get_packages(args)
+        package_names = sorted(p["name"] for p in pkgs)
+        print(package_names)
+
+    assert package_names == ["pip", "setuptools"]
+
+
 def test_fail_on(monkeypatch) -> None:
     licenses = ("MIT license",)
     allow_only_args = ["--fail-on={}".format(";".join(licenses))]