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"""Implement https://www.python.org/dev/peps/pep-0514/ to discover interpreters - Windows only"""
from __future__ import annotations
import os
import re
import winreg
from logging import basicConfig, getLogger
LOGGER = getLogger(__name__)
def enum_keys(key):
at = 0
while True:
try:
yield winreg.EnumKey(key, at)
except OSError:
break
at += 1
def get_value(key, value_name):
try:
return winreg.QueryValueEx(key, value_name)[0]
except OSError:
return None
def discover_pythons():
for hive, hive_name, key, flags, default_arch in [
(winreg.HKEY_CURRENT_USER, "HKEY_CURRENT_USER", r"Software\Python", 0, 64),
(winreg.HKEY_LOCAL_MACHINE, "HKEY_LOCAL_MACHINE", r"Software\Python", winreg.KEY_WOW64_64KEY, 64),
(winreg.HKEY_LOCAL_MACHINE, "HKEY_LOCAL_MACHINE", r"Software\Python", winreg.KEY_WOW64_32KEY, 32),
]:
yield from process_set(hive, hive_name, key, flags, default_arch)
def process_set(hive, hive_name, key, flags, default_arch):
try:
with winreg.OpenKeyEx(hive, key, 0, winreg.KEY_READ | flags) as root_key:
for company in enum_keys(root_key):
if company == "PyLauncher": # reserved
continue
yield from process_company(hive_name, company, root_key, default_arch)
except OSError:
pass
def process_company(hive_name, company, root_key, default_arch):
with winreg.OpenKeyEx(root_key, company) as company_key:
for tag in enum_keys(company_key):
spec = process_tag(hive_name, company, company_key, tag, default_arch)
if spec is not None:
yield spec
def process_tag(hive_name, company, company_key, tag, default_arch):
with winreg.OpenKeyEx(company_key, tag) as tag_key:
version = load_version_data(hive_name, company, tag, tag_key)
if version is not None: # if failed to get version bail
major, minor, _ = version
arch = load_arch_data(hive_name, company, tag, tag_key, default_arch)
if arch is not None:
exe_data = load_exe(hive_name, company, company_key, tag)
if exe_data is not None:
exe, args = exe_data
return company, major, minor, arch, exe, args
def load_exe(hive_name, company, company_key, tag):
key_path = f"{hive_name}/{company}/{tag}"
try:
with winreg.OpenKeyEx(company_key, rf"{tag}\InstallPath") as ip_key:
with ip_key:
exe = get_value(ip_key, "ExecutablePath")
if exe is None:
ip = get_value(ip_key, None)
if ip is None:
msg(key_path, "no ExecutablePath or default for it")
else:
exe = os.path.join(ip, "python.exe")
if exe is not None and os.path.exists(exe):
args = get_value(ip_key, "ExecutableArguments")
return exe, args
else:
msg(key_path, f"could not load exe with value {exe}")
except OSError:
msg(f"{key_path}/InstallPath", "missing")
return None
def load_arch_data(hive_name, company, tag, tag_key, default_arch):
arch_str = get_value(tag_key, "SysArchitecture")
if arch_str is not None:
key_path = f"{hive_name}/{company}/{tag}/SysArchitecture"
try:
return parse_arch(arch_str)
except ValueError as sys_arch:
msg(key_path, sys_arch)
return default_arch
def parse_arch(arch_str):
if isinstance(arch_str, str):
match = re.match(r"^(\d+)bit$", arch_str)
if match:
return int(next(iter(match.groups())))
error = f"invalid format {arch_str}"
else:
error = f"arch is not string: {repr(arch_str)}"
raise ValueError(error)
def load_version_data(hive_name, company, tag, tag_key):
for candidate, key_path in [
(get_value(tag_key, "SysVersion"), f"{hive_name}/{company}/{tag}/SysVersion"),
(tag, f"{hive_name}/{company}/{tag}"),
]:
if candidate is not None:
try:
return parse_version(candidate)
except ValueError as sys_version:
msg(key_path, sys_version)
return None
def parse_version(version_str):
if isinstance(version_str, str):
match = re.match(r"^(\d+)(?:\.(\d+))?(?:\.(\d+))?$", version_str)
if match:
return tuple(int(i) if i is not None else None for i in match.groups())
error = f"invalid format {version_str}"
else:
error = f"version is not string: {version_str!r}"
raise ValueError(error)
def msg(path, what):
LOGGER.warning(f"PEP-514 violation in Windows Registry at {path} error: {what}")
def _run():
basicConfig()
interpreters = []
for spec in discover_pythons():
interpreters.append(repr(spec))
print("\n".join(sorted(interpreters)))
if __name__ == "__main__":
_run()
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