当我在 Rust 中使用 pyo3 构建 python 库时出现错误“根目录中没有 py”

Question

我的环境

• Ubuntu 18.04
• Rust 1.39.0-nightly
• Python 3.7.3

我想做什么和问题

我想为 python 编写一个库。作为我的实践，我尝试了文档中的代码。

Cargo.toml

[package]
name = "example"
version = "0.1.0"
authors = ["Yudai Hayashi"]
edition = "2018"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
[lib]
name = "example"
crate-type = ["cdylib"]

[dependencies]

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

src/lib.rs

#![feature(proc_macro, specialization)]

extern crate pyo3;
use pyo3::{py, PyResult, Python, PyModule};

use pyo3::py::modinit as pymodinit;

// add bindings to the generated python module
// N.B: names: "librust2py" must be the name of the `.so` or `.pyd` file
/// This module is implemented in Rust.
#[pymodinit(rust2py)]
fn init_mod(py: Python, m: &PyModule) -> PyResult<()> {

    #[pyfn(m, "sum_as_string")]
    // pyo3 aware function. All of our python interface could be declared in a separate module.
    // Note that the `#[pyfn()]` annotation automatically converts the arguments from
    // Python objects to Rust values; and the Rust return value back into a Python object.
    fn sum_as_string_py(_: Python, a:i64, b:i64) -> PyResult<String> {
       let out = sum_as_string(a, b);
       Ok(out)
    }

    Ok(())
}

// logic implemented as a normal Rust function
fn sum_as_string(a:i64, b:i64) -> String {
    format!("{}", a + b).to_string()
}

当我构建这个程序时，我遇到了一些错误。

error[E0432]: unresolved import `pyo3::py`
 --> src/lib.rs:4:12
  |
4 | use pyo3::{py, PyResult, Python, PyModule};
  |            ^^
  |            |
  |            no `py` in the root
  |            help: a similar name exists in the module: `Py`

error[E0432]: unresolved import `pyo3::py`
 --> src/lib.rs:6:11
  |
6 | use pyo3::py::modinit as pymodinit;
  |           ^^ could not find `py` in `pyo3`

error: cannot determine resolution for the attribute macro `pymodinit`
  --> src/lib.rs:11:3
   |
11 | #[pymodinit(rust2py)]
   |   ^^^^^^^^^
   |
   = note: import resolution is stuck, try simplifying macro imports

error: cannot find attribute macro `pyfn` in this scope
  --> src/lib.rs:14:7
   |
14 |     #[pyfn(m, "sum_as_string")]
   |       ^^^^

error: aborting due to 4 previous errors

For more information about this error, try `rustc --explain E0432`.
error: Could not compile `example`.

此错误消息表明 pyo3 模块中没有“py”。我查找了此错误消息，但找不到类似的错误。

如何处理这个问题？

Answer 1

pyo3的最新版本中有no mod called py。您已经获得了与旧版本库相关的文档或示例。具有此 mod 的最后一个版本是 0.2.7。

如果您除了运行代码之外没有兴趣，请将您需要的 pyo3 版本在您的 Cargo.toml 依赖项中设置为 0.2.7，它应该可以立即编译（粗略一瞥确认所有符号似乎存在于该版本中）。

如果您想真正研究较新的版本，the new documentation 有最新的示例。