pyo3/types/
traceback.rs

1use crate::err::{error_on_minusone, PyResult};
2use crate::types::{any::PyAnyMethods, string::PyStringMethods, PyString};
3use crate::{ffi, Bound, PyAny};
4
5/// Represents a Python traceback.
6///
7/// Values of this type are accessed via PyO3's smart pointers, e.g. as
8/// [`Py<PyTraceback>`][crate::Py] or [`Bound<'py, PyTraceback>`][Bound].
9///
10/// For APIs available on traceback objects, see the [`PyTracebackMethods`] trait which is implemented for
11/// [`Bound<'py, PyTraceback>`][Bound].
12#[repr(transparent)]
13pub struct PyTraceback(PyAny);
14
15pyobject_native_type_core!(
16    PyTraceback,
17    pyobject_native_static_type_object!(ffi::PyTraceBack_Type),
18    #checkfunction=ffi::PyTraceBack_Check
19);
20
21/// Implementation of functionality for [`PyTraceback`].
22///
23/// These methods are defined for the `Bound<'py, PyTraceback>` smart pointer, so to use method call
24/// syntax these methods are separated into a trait, because stable Rust does not yet support
25/// `arbitrary_self_types`.
26#[doc(alias = "PyTraceback")]
27pub trait PyTracebackMethods<'py>: crate::sealed::Sealed {
28    /// Formats the traceback as a string.
29    ///
30    /// This does not include the exception type and value. The exception type and value can be
31    /// formatted using the `Display` implementation for `PyErr`.
32    ///
33    /// # Example
34    ///
35    /// The following code formats a Python traceback and exception pair from Rust:
36    ///
37    /// ```rust
38    /// # use pyo3::{Python, PyResult, prelude::PyTracebackMethods, ffi::c_str};
39    /// # let result: PyResult<()> =
40    /// Python::attach(|py| {
41    ///     let err = py
42    ///         .run(c"raise Exception('banana')", None, None)
43    ///         .expect_err("raise will create a Python error");
44    ///
45    ///     let traceback = err.traceback(py).expect("raised exception will have a traceback");
46    ///     assert_eq!(
47    ///         format!("{}{}", traceback.format()?, err),
48    ///         "\
49    /// Traceback (most recent call last):
50    ///   File \"<string>\", line 1, in <module>
51    /// Exception: banana\
52    /// "
53    ///     );
54    ///     Ok(())
55    /// })
56    /// # ;
57    /// # result.expect("example failed");
58    /// ```
59    fn format(&self) -> PyResult<String>;
60}
61
62impl<'py> PyTracebackMethods<'py> for Bound<'py, PyTraceback> {
63    fn format(&self) -> PyResult<String> {
64        let py = self.py();
65        let string_io = py
66            .import(intern!(py, "io"))?
67            .getattr(intern!(py, "StringIO"))?
68            .call0()?;
69        let result = unsafe { ffi::PyTraceBack_Print(self.as_ptr(), string_io.as_ptr()) };
70        error_on_minusone(py, result)?;
71        let formatted = string_io
72            .getattr(intern!(py, "getvalue"))?
73            .call0()?
74            .cast::<PyString>()?
75            .to_cow()?
76            .into_owned();
77        Ok(formatted)
78    }
79}
80
81#[cfg(test)]
82mod tests {
83    use crate::IntoPyObject;
84    use crate::{
85        types::{any::PyAnyMethods, dict::PyDictMethods, traceback::PyTracebackMethods, PyDict},
86        PyErr, Python,
87    };
88
89    #[test]
90    fn format_traceback() {
91        Python::attach(|py| {
92            let err = py
93                .run(c"raise Exception('banana')", None, None)
94                .expect_err("raising should have given us an error");
95
96            assert_eq!(
97                err.traceback(py).unwrap().format().unwrap(),
98                "Traceback (most recent call last):\n  File \"<string>\", line 1, in <module>\n"
99            );
100        })
101    }
102
103    #[test]
104    fn test_err_from_value() {
105        Python::attach(|py| {
106            let locals = PyDict::new(py);
107            // Produce an error from python so that it has a traceback
108            py.run(
109                cr"
110try:
111    raise ValueError('raised exception')
112except Exception as e:
113    err = e
114",
115                None,
116                Some(&locals),
117            )
118            .unwrap();
119            let err = PyErr::from_value(locals.get_item("err").unwrap().unwrap());
120            let traceback = err.value(py).getattr("__traceback__").unwrap();
121            assert!(err.traceback(py).unwrap().is(&traceback));
122        })
123    }
124
125    #[test]
126    fn test_err_into_py() {
127        Python::attach(|py| {
128            let locals = PyDict::new(py);
129            // Produce an error from python so that it has a traceback
130            py.run(
131                cr"
132def f():
133    raise ValueError('raised exception')
134",
135                None,
136                Some(&locals),
137            )
138            .unwrap();
139            let f = locals.get_item("f").unwrap().unwrap();
140            let err = f.call0().unwrap_err();
141            let traceback = err.traceback(py).unwrap();
142            let err_object = err.clone_ref(py).into_pyobject(py).unwrap();
143
144            assert!(err_object.getattr("__traceback__").unwrap().is(&traceback));
145        })
146    }
147}
pyo3/types/traceback.rs

pyo3/types/
traceback.rs
