Python 相对导入报错：用 -m、包入口和 Linux 启动脚本修复

python3 --version
python3 --help
mkdir relative-import-demo
cd relative-import-demo
demo_root="$PWD"
mkdir triage_demo data
: > triage_demo/__init__.py
printf 'alpha\nbeta\ngamma\n' > data/items.txt

from pathlib import Path


def count_lines(filename):
    with Path(filename).open(encoding="utf-8") as source:
        return sum(1 for _ in source)

import argparse
import sys

from .helpers import count_lines


def main():
    parser = argparse.ArgumentParser(description="Count UTF-8 text lines.")
    parser.add_argument("input", help="text file to read")
    args = parser.parse_args()
    try:
        lines = count_lines(args.input)
    except (OSError, UnicodeError) as exc:
        print(f"ERROR: {exc}", file=sys.stderr)
        return 1
    print(f"lines={lines}")
    return 0


if __name__ == "__main__":
    raise SystemExit(main())

if python3 triage_demo/cli.py data/items.txt; then
  printf 'Unexpected success: inspect the package and environment\n'
else
  printf 'Expected failure: direct file execution lost package context\n'
fi

ImportError: attempted relative import with no known parent package

python3 -m triage_demo.cli --help
python3 -m triage_demo.cli data/items.txt

python3 -c 'import triage_demo.cli as m; print(m.__name__); print(m.__package__)'

from .cli import main

if __name__ == "__main__":
    raise SystemExit(main())

python3 -m triage_demo data/items.txt

#!/bin/sh
set -eu
project_dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
cd -- "$project_dir"
exec "${PYTHON:-python3}" -m triage_demo "$@"

chmod u+x launch.sh
(
  cd /
  sh "$demo_root/launch.sh" data/items.txt
)

from pathlib import Path
import os
import subprocess
import sys
import tempfile

root = Path(__file__).resolve().parent
env = os.environ.copy()
for key in list(env):
    if key.startswith("PYTHON"):
        del env[key]
env["PYTHON"] = sys.executable


def run(args, cwd):
    return subprocess.run(
        args, cwd=cwd, env=env, capture_output=True,
        text=True, timeout=10, check=False,
    )


with tempfile.TemporaryDirectory(prefix="module-entry-test-") as tmp:
    outside = Path(tmp)
    source = outside / "input with spaces.txt"
    source.write_text("alpha\n\ngamma\n", encoding="utf-8")
    path = str(source)

    direct = run([sys.executable, "triage_demo/cli.py", path], root)
    assert direct.returncode == 1 and not direct.stdout, direct
    assert "attempted relative import" in direct.stderr, direct

    for module in ["triage_demo.cli", "triage_demo"]:
        good = run([sys.executable, "-m", module, path], root)
        assert (good.returncode, good.stdout, good.stderr) == (0, "lines=3\n", ""), good

    foreign = run([sys.executable, "-m", "triage_demo", path], outside)
    assert foreign.returncode != 0 and "No module named triage_demo" in foreign.stderr, foreign

    wrapped = run(["sh", str(root / "launch.sh"), path], outside)
    assert (wrapped.returncode, wrapped.stdout, wrapped.stderr) == (0, "lines=3\n", ""), wrapped

    help_result = run([sys.executable, "-m", "triage_demo", "--help"], root)
    assert help_result.returncode == 0 and "Count UTF-8 text lines." in help_result.stdout, help_result
    no_arg = run([sys.executable, "-m", "triage_demo"], root)
    assert no_arg.returncode == 2 and "required" in no_arg.stderr, no_arg
    missing = run([sys.executable, "-m", "triage_demo", str(outside / "missing.txt")], root)
    assert missing.returncode == 1 and missing.stderr.startswith("ERROR:"), missing
    bad = outside / "bad.txt"
    bad.write_bytes(b"\xff")
    encoding = run([sys.executable, "-m", "triage_demo", str(bad)], root)
    assert encoding.returncode == 1 and "ERROR:" in encoding.stderr, encoding
    imported = run([sys.executable, "-c", "import triage_demo.cli; import triage_demo.__main__; print('import OK')"], root)
    assert (imported.returncode, imported.stdout, imported.stderr) == (0, "import OK\n", ""), imported

print("OK: direct failure, module entry, package entry, foreign cwd, launcher, help, errors, safe import")

python3 verify_demo.py

OK: direct failure, module entry, package entry, foreign cwd, launcher, help, errors, safe import