# iterator.rs - source
Source of the Rust file `/home/runner/.cargo/registry/src/github.com-1ecc6299db9ec823/pyo3-0.13.2/src/types/iterator.rs`.
Keywords: rust, rustlang, rust-lang

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    // Copyright (c) 2017-present PyO3 Project and Contributors
    //
    // based on Daniel Grunwald's https://github.com/dgrunwald/rust-cpython

    use crate::{ffi, AsPyPointer, PyAny, PyErr, PyNativeType, PyResult, Python};
    #[cfg(any(not(Py_LIMITED_API), Py_3_8))]
    use crate::{PyDowncastError, PyTryFrom};

    /// A Python iterator object.
    ///
    /// # Example
    ///
    /// ```rust
    /// # use pyo3::prelude::*;
    /// use pyo3::types::PyIterator;
    ///
    /// # fn main() -> PyResult<()> {
    /// let gil = Python::acquire_gil();
    /// let py = gil.python();
    /// let list = py.eval("iter([1, 2, 3, 4])", None, None)?;
    /// let numbers: PyResult<Vec<usize>> = list.iter()?.map(|i| i.and_then(PyAny::extract::<usize>)).collect();
    /// let sum: usize = numbers?.iter().sum();
    /// assert_eq!(sum, 10);
    /// # Ok(())
    /// # }
    /// ```
    #[repr(transparent)]
    pub struct PyIterator(PyAny);
    pyobject_native_type_named!(PyIterator);
    #[cfg(any(not(Py_LIMITED_API), Py_3_8))]
    pyobject_native_type_extract!(PyIterator);

    impl PyIterator {
        /// Constructs a `PyIterator` from a Python iterable object.
        ///
        /// Equivalent to Python's built-in `iter` function.
        pub fn from_object<'p, T>(py: Python<'p>, obj: &T) -> PyResult<&'p PyIterator>
        where
            T: AsPyPointer,
        {
            unsafe { py.from_owned_ptr_or_err(ffi::PyObject_GetIter(obj.as_ptr())) }
        }
    }

    impl<'p> Iterator for &'p PyIterator {
        type Item = PyResult<&'p PyAny>;

        /// Retrieves the next item from an iterator.
        ///
        /// Returns `None` when the iterator is exhausted.
        /// If an exception occurs, returns `Some(Err(..))`.
        /// Further `next()` calls after an exception occurs are likely
        /// to repeatedly result in the same exception.
        fn next(&mut self) -> Option<Self::Item> {
            let py = self.0.py();

            match unsafe { py.from_owned_ptr_or_opt(ffi::PyIter_Next(self.0.as_ptr())) } {
                Some(obj) => Some(Ok(obj)),
                None => {
                    if PyErr::occurred(py) {
                        Some(Err(PyErr::fetch(py)))
                    } else {
                        None
                    }
                }
            }
        }
    }

    // PyIter_Check does not exist in the limited API until 3.8
    #[cfg(any(not(Py_LIMITED_API), Py_3_8))]
    impl<'v> PyTryFrom<'v> for PyIterator {
        fn try_from<V: Into<&'v PyAny>>(value: V) -> Result<&'v PyIterator, PyDowncastError<'v>> {
            let value = value.into();
            unsafe {
                if ffi::PyIter_Check(value.as_ptr()) != 0 {
                    Ok(<PyIterator as PyTryFrom>::try_from_unchecked(value))
                } else {
                    Err(PyDowncastError::new(value, "Iterator"))
                }
            }
        }

        fn try_from_exact<V: Into<&'v PyAny>>(value: V) -> Result<&'v PyIterator, PyDowncastError<'v>> {
            <PyIterator as PyTryFrom>::try_from(value)
        }

        #[inline]
        unsafe fn try_from_unchecked<V: Into<&'v PyAny>>(value: V) -> &'v PyIterator {
            let ptr = value.into() as *const _ as *const PyIterator;
            &*ptr
        }
    }

    #[cfg(test)]
    mod tests {
        use super::PyIterator;
        use crate::exceptions::PyTypeError;
        use crate::gil::GILPool;
        use crate::types::{PyDict, PyList};
        #[cfg(any(not(Py_LIMITED_API), Py_3_8))]
        use crate::{Py, PyAny, PyTryFrom};
        use crate::{Python, ToPyObject};
        use indoc::indoc;

        #[test]
        fn vec_iter() {
            let gil_guard = Python::acquire_gil();
            let py = gil_guard.python();
            let obj = vec![10, 20].to_object(py);
            let inst = obj.as_ref(py);
            let mut it = inst.iter().unwrap();
            assert_eq!(10, it.next().unwrap().unwrap().extract().unwrap());
            assert_eq!(20, it.next().unwrap().unwrap().extract().unwrap());
            assert!(it.next().is_none());
        }

        #[test]
        fn iter_refcnt() {
            let obj;
            let count;
            {
                let gil_guard = Python::acquire_gil();
                let py = gil_guard.python();
                obj = vec![10, 20].to_object(py);
                count = obj.get_refcnt(py);
            }

            {
                let gil_guard = Python::acquire_gil();
                let py = gil_guard.python();
                let inst = obj.as_ref(py);
                let mut it = inst.iter().unwrap();

                assert_eq!(10, it.next().unwrap().unwrap().extract().unwrap());
            }
            assert_eq!(count, obj.get_refcnt(Python::acquire_gil().python()));
        }

        #[test]
        fn iter_item_refcnt() {
            let gil_guard = Python::acquire_gil();
            let py = gil_guard.python();

            let obj;
            let none;
            let count;
            {
                let _pool = unsafe { GILPool::new() };
                let l = PyList::empty(py);
                none = py.None();
                l.append(10).unwrap();
                l.append(&none).unwrap();
                count = none.get_refcnt(py);
                obj = l.to_object(py);
            }

            {
                let _pool = unsafe { GILPool::new() };
                let inst = obj.as_ref(py);
                let mut it = inst.iter().unwrap();

                assert_eq!(10, it.next().unwrap().unwrap().extract().unwrap());
                assert!(it.next().unwrap().unwrap().is_none());
            }
            assert_eq!(count, none.get_refcnt(py));
        }

        #[test]
        fn fibonacci_generator() {
            let fibonacci_generator = indoc!(
                r#"
                def fibonacci(target):
                    a = 1
                    b = 1
                    for _ in range(target):
                        yield a
                        a, b = b, a + b
            "#
            );

            let gil = Python::acquire_gil();
            let py = gil.python();

            let context = PyDict::new(py);
            py.run(fibonacci_generator, None, Some(context)).unwrap();

            let generator = py.eval("fibonacci(5)", None, Some(context)).unwrap();
            for (actual, expected) in generator.iter().unwrap().zip(&[1, 1, 2, 3, 5]) {
                let actual = actual.unwrap().extract::<usize>().unwrap();
                assert_eq!(actual, *expected)
            }
        }

        #[test]
        fn int_not_iterable() {
            let gil = Python::acquire_gil();
            let py = gil.python();

            let x = 5.to_object(py);
            let err = PyIterator::from_object(py, &x).unwrap_err();

            assert!(err.is_instance::<PyTypeError>(py))
        }

        #[test]
        #[cfg(any(not(Py_LIMITED_API), Py_3_8))]
        fn iterator_try_from() {
            let gil_guard = Python::acquire_gil();
            let py = gil_guard.python();
            let obj: Py<PyAny> = vec![10, 20].to_object(py).as_ref(py).iter().unwrap().into();
            let iter: &PyIterator = PyIterator::try_from(obj.as_ref(py)).unwrap();
            assert_eq!(obj, iter.into());
        }
    }