运行pytest时，使用PyO3和rustcpython生成的Rust库不会导入

Question

在遵循各种有关编译锈库以便从Python进一步导入的教程（我尝试了PyO3和rust-cpython）的同时，我已经能够构建一个简单的库，并成功地从我的main.py和交互式Python shell导入它

然而，当尝试测试和基准测试纯Python与我的Rust库时，我始终会遇到导入错误：

_____________________________________________ ERROR collecting main.py _____________________________________________
ImportError while importing test module '/Users/xxx/pyo3/sumlib/main.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/Users/xxx/.pyenv/versions/3.8.2/lib/python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
main.py:1: in <module>
    import sumlib
E   ModuleNotFoundError: No module named 'sumlib'

同样，该库从主python文件和交互式shell（如IPython）导入的效果很好

我在macOS Big Sur上，Python 3.8是使用pyenv安装的。这是我的Cargo.toml：

[package]
name = "sumlib"
version = "0.1.0"
edition = "2018"

[lib]
name = "sumlib"
# "cdylib" is necessary to produce a shared library for Python to import from.
#
# Downstream Rust code (including code in `bin/`, `examples/`, and `tests/`) will not be able
# to `use string_sum;` unless the "rlib" or "lib" crate type is also included, e.g.:
# crate-type = ["cdylib", "rlib"]
crate-type = ["cdylib", "rlib"]

[dependencies.pyo3]
version = "0.14.2"
features = ["extension-module"]

从PyO3和rust-cpython到相同的结果，其他一切都非常琐碎

Answer 1

tl/dr：使用python -m pytest而不是pytest调用测试

---

听起来您好像还没有安装Python扩展模块（例如，使用pip install），而是依赖于它位于您的工作目录中。这将允许您使用解释器或通过python -m启动的main.py导入它

$ tree .
.
├── bin
│   ├── __init__.py
│   └── sumlib.py
└── examples
    └── main.py

2 directories, 3 files
$ ipython  no-banner

In [1]: from bin import sumlib

In [2]: exit()

$ python -m examples.main
Successfully imported sumlib!

但不使用pytest examples/main.py或python examples/main.py

$ pytest examples/main.py
======================================================= test session starts =======================================================
platform darwin   Python 3.8.3, pytest-6.2.4, py-1.10.0, pluggy-0.13.1
rootdir: ...
plugins: typeguard-2.10.0
collected 0 items / 1 error

============================================================= ERRORS ==============================================================
________________________________________________ ERROR collecting examples/main.py ________________________________________________
ImportError while importing test module '.../examples/main.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
.../python3.8/importlib/__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
examples/main.py:5: in <module>
    from bin import sumlib
E   ModuleNotFoundError: No module named 'bin'
...
$ python examples/main.py
Traceback (most recent call last):
  File "examples/main.py", line 5, in <module>
    from bin import sumlib
ModuleNotFoundError: No module named 'bin'

这是因为ipython和python -m都将包含扩展模块的当前目录添加到Python的sys.path，但是pytest examples/main.py和python examples/main.py没有。（请参阅pytest docs。）您可以通过安装扩展模块或使用python -m pytest而不是pytest运行测试来解决此问题