import sys

print(sys.version_info >= (3, 10))          # True
print(type(sys.argv).__name__)               # list   ← ["script.py", "arg1", ...]
print(isinstance(sys.path, list))            # True   ← where imports are searched
print(sys.maxsize == 2**63 - 1)              # True   ← on 64-bit builds
print(sys.getrecursionlimit())               # 1000

import os

os.environ["APP_MODE"] = "test"                     # visible to child processes too
print(os.environ.get("APP_MODE"))                   # test
print(os.environ.get("NOT_SET_ANYWHERE", "default"))  # default
print(os.getenv("NOT_SET_ANYWHERE") is None)        # True
print(os.path.join("data", "2026", "report.csv"))   # data/2026/report.csv
print(os.path.splitext("photo.tar.gz"))             # ('photo.tar', '.gz')
print(os.sep, os.cpu_count() > 0)                   # / True
del os.environ["APP_MODE"]

import os, tempfile

root = tempfile.mkdtemp()
for rel in ["src/app.py", "src/util.py", "docs/index.md", "README.md"]:
    path = os.path.join(root, rel)
    os.makedirs(os.path.dirname(path), exist_ok=True)
    open(path, "w").close()

print(sorted(os.listdir(root)))                      # ['README.md', 'docs', 'src']
with os.scandir(root) as entries:                    # faster: file type info included
    print(sorted(e.name for e in entries if e.is_dir()))   # ['docs', 'src']

found = []
for dirpath, dirnames, filenames in os.walk(root):
    found += [f for f in filenames if f.endswith(".py")]
print(sorted(found))                                 # ['app.py', 'util.py']

import shutil, tempfile
from pathlib import Path

base = Path(tempfile.mkdtemp())
(base / "src").mkdir()
(base / "src" / "a.txt").write_text("hello")

shutil.copy(base / "src" / "a.txt", base / "b.txt")        # copy one file
shutil.copytree(base / "src", base / "backup")             # copy a whole tree
shutil.move(base / "b.txt", base / "c.txt")                # move / rename
shutil.rmtree(base / "src")                                # delete a tree — careful!
print(sorted(p.name for p in base.iterdir()))              # ['backup', 'c.txt']
print(shutil.which("definitely-not-a-real-cmd"))           # None
archive = shutil.make_archive(str(base / "bundle"), "zip", base / "backup")
print(Path(archive).name)                                  # bundle.zip

import subprocess, sys

result = subprocess.run(
    [sys.executable, "-c", "print('hello from a child process')"],
    capture_output=True, text=True,
)
print(result.returncode, result.stdout.strip())   # 0 hello from a child process

try:
    subprocess.run([sys.executable, "-c", "raise SystemExit(2)"], check=True)
except subprocess.CalledProcessError as e:
    print("failed with", e.returncode)            # failed with 2

out = subprocess.run([sys.executable, "-c", "import sys; print(sys.stdin.read().upper())"],
                     input="piped text", capture_output=True, text=True, timeout=10)
print(out.stdout.strip())                          # PIPED TEXT