From fc34e4116390143fe364d79fa8cf3a14f76add96 Mon Sep 17 00:00:00 2001
From: David Hewitt <1939362+davidhewitt@users.noreply.github.com>
Date: Sun, 15 Nov 2020 14:30:21 +0000
Subject: [PATCH] pyany: add is_instance

---
 CHANGELOG.md           |  1 +
 guide/src/exception.md | 12 ++++++------
 src/types/any.rs       | 29 ++++++++++++++++++++++++-----
 3 files changed, 31 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2776b644..12cd6f72 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 - Add FFI definitions for PEP 587 "Python Initialization Configuration". [#1247](https://github.com/PyO3/pyo3/pull/1247)
 - Add `PyEval_SetProfile` and `PyEval_SetTrace` to FFI. [#1255](https://github.com/PyO3/pyo3/pull/1255)
 - Add context.h functions (`PyContext_New`, etc) to FFI. [#1259](https://github.com/PyO3/pyo3/pull/1259)
+- Add `PyAny::is_instance()` method. [#1276](https://github.com/PyO3/pyo3/pull/1276)
 - Add support for conversion between `char` and `PyString`. [#1282](https://github.com/PyO3/pyo3/pull/1282)
 
 ### Changed
diff --git a/guide/src/exception.md b/guide/src/exception.md
index 62ab6422..20c21da7 100644
--- a/guide/src/exception.md
+++ b/guide/src/exception.md
@@ -96,8 +96,8 @@ fn my_func(arg: PyObject) -> PyResult<()> {
 
 ## Checking exception types
 
-Python has an [`isinstance`](https://docs.python.org/3/library/functions.html#isinstance) method to check an object's type,
-in PyO3 there is a [`Python::is_instance`] method which does the same thing.
+Python has an [`isinstance`](https://docs.python.org/3/library/functions.html#isinstance) method to check an object's type.
+In PyO3 every native type has access to the [`PyAny::is_instance`] method which does the same thing.
 
 ```rust
 use pyo3::Python;
@@ -106,13 +106,13 @@ use pyo3::types::{PyBool, PyList};
 fn main() {
     let gil = Python::acquire_gil();
     let py = gil.python();
-    assert!(py.is_instance::<PyBool, _>(PyBool::new(py, true)).unwrap());
+    assert!(PyBool::new(py, true).is_instance::<PyBool>().unwrap());
     let list = PyList::new(py, &[1, 2, 3, 4]);
-    assert!(!py.is_instance::<PyBool, _>(list.as_ref()).unwrap());
-    assert!(py.is_instance::<PyList, _>(list.as_ref()).unwrap());
+    assert!(!list.is_instance::<PyBool>().unwrap());
+    assert!(list.is_instance::<PyList>().unwrap());
 }
 ```
-[`Python::is_instance`] calls the underlying [`PyType::is_instance`](https://docs.rs/pyo3/latest/pyo3/types/struct.PyType.html#method.is_instance)
+[`PyAny::is_instance`] calls the underlying [`PyType::is_instance`](https://docs.rs/pyo3/latest/pyo3/types/struct.PyType.html#method.is_instance)
 method to do the actual work.
 
 To check the type of an exception, you can similarly do:
diff --git a/src/types/any.rs b/src/types/any.rs
index faf0b119..1a79aa58 100644
--- a/src/types/any.rs
+++ b/src/types/any.rs
@@ -4,6 +4,7 @@ use crate::conversion::{
 };
 use crate::err::{PyDowncastError, PyErr, PyResult};
 use crate::exceptions::PyTypeError;
+use crate::type_object::PyTypeObject;
 use crate::types::{PyDict, PyIterator, PyList, PyString, PyTuple, PyType};
 use crate::{err, ffi, Py, PyNativeType, PyObject};
 use libc::c_int;
@@ -29,8 +30,8 @@ use std::cmp::Ordering;
 /// use pyo3::types::{PyAny, PyDict, PyList};
 /// let gil = Python::acquire_gil();
 /// let dict = PyDict::new(gil.python());
-/// assert!(gil.python().is_instance::<PyAny, _>(dict).unwrap());
-/// let any = dict.as_ref();
+/// assert!(dict.is_instance::<PyAny>().unwrap());
+/// let any: &PyAny = dict.as_ref();
 /// assert!(any.downcast::<PyDict>().is_ok());
 /// assert!(any.downcast::<PyList>().is_err());
 /// ```
@@ -452,13 +453,19 @@ impl PyAny {
     pub fn dir(&self) -> &PyList {
         unsafe { self.py().from_owned_ptr(ffi::PyObject_Dir(self.as_ptr())) }
     }
+
+    /// Checks whether this object is an instance of type `T`.
+    ///
+    /// This is equivalent to the Python expression `isinstance(self, T)`.
+    pub fn is_instance<T: PyTypeObject>(&self) -> PyResult<bool> {
+        T::type_object(self.py()).is_instance(self)
+    }
 }
 
 #[cfg(test)]
 mod test {
-    use crate::types::{IntoPyDict, PyList};
-    use crate::Python;
-    use crate::ToPyObject;
+    use crate::types::{IntoPyDict, PyList, PyLong};
+    use crate::{Python, ToPyObject};
 
     #[test]
     fn test_call_for_non_existing_method() {
@@ -514,4 +521,16 @@ mod test {
         let nan = py.eval("float('nan')", None, None).unwrap();
         assert!(nan.compare(nan).is_err());
     }
+
+    #[test]
+    fn test_any_isinstance() {
+        let gil = Python::acquire_gil();
+        let py = gil.python();
+
+        let x = 5.to_object(py).into_ref(py);
+        assert!(x.is_instance::<PyLong>().unwrap());
+
+        let l = vec![x, x].to_object(py).into_ref(py);
+        assert!(l.is_instance::<PyList>().unwrap());
+    }
 }