polars_python/interop/numpy/
to_numpy_series.rs

1use ndarray::IntoDimension;
2use num_traits::{Float, NumCast};
3use numpy::npyffi::flags;
4use numpy::{Element, PyArray1};
5use polars_core::prelude::*;
6use pyo3::exceptions::PyRuntimeError;
7use pyo3::prelude::*;
8use pyo3::{IntoPyObjectExt, intern};
9
10use super::to_numpy_df::df_to_numpy;
11use super::utils::{
12    create_borrowed_np_array, dtype_supports_view, polars_dtype_to_np_temporal_dtype,
13    reshape_numpy_array, series_contains_null,
14};
15use crate::conversion::ObjectValue;
16use crate::conversion::chunked_array::{decimal_to_pyobject_iter, time_to_pyobject_iter};
17use crate::series::PySeries;
18
19#[pymethods]
20impl PySeries {
21    /// Convert this Series to a NumPy ndarray.
22    ///
23    /// This method copies data only when necessary. Set `allow_copy` to raise an error if copy
24    /// is required. Set `writable` to make sure the resulting array is writable, possibly requiring
25    /// copying the data.
26    fn to_numpy(&self, py: Python<'_>, writable: bool, allow_copy: bool) -> PyResult<Py<PyAny>> {
27        series_to_numpy(py, &self.series.read(), writable, allow_copy)
28    }
29
30    /// Create a view of the data as a NumPy ndarray.
31    ///
32    /// WARNING: The resulting view will show the underlying value for nulls,
33    /// which may be any value. The caller is responsible for handling nulls
34    /// appropriately.
35    fn to_numpy_view(&self, py: Python) -> Option<Py<PyAny>> {
36        let (view, _) = try_series_to_numpy_view(py, &self.series.read(), true, false)?;
37        Some(view)
38    }
39}
40
41/// Convert a Series to a NumPy ndarray.
42pub(super) fn series_to_numpy(
43    py: Python<'_>,
44    s: &Series,
45    writable: bool,
46    allow_copy: bool,
47) -> PyResult<Py<PyAny>> {
48    if s.is_empty() {
49        // Take this path to ensure a writable array.
50        // This does not actually copy data for an empty Series.
51        return Ok(series_to_numpy_with_copy(py, s, true));
52    }
53    if let Some((mut arr, writable_flag)) = try_series_to_numpy_view(py, s, false, allow_copy) {
54        if writable && !writable_flag {
55            if !allow_copy {
56                return Err(PyRuntimeError::new_err(
57                    "copy not allowed: cannot create a writable array without copying data",
58                ));
59            }
60            arr = arr.call_method0(py, intern!(py, "copy"))?;
61        }
62        return Ok(arr);
63    }
64
65    if !allow_copy {
66        return Err(PyRuntimeError::new_err(
67            "copy not allowed: cannot convert to a NumPy array without copying data",
68        ));
69    }
70
71    Ok(series_to_numpy_with_copy(py, s, writable))
72}
73
74/// Create a NumPy view of the given Series.
75fn try_series_to_numpy_view(
76    py: Python<'_>,
77    s: &Series,
78    allow_nulls: bool,
79    allow_rechunk: bool,
80) -> Option<(Py<PyAny>, bool)> {
81    if !dtype_supports_view(s.dtype()) {
82        return None;
83    }
84    if !allow_nulls && series_contains_null(s) {
85        return None;
86    }
87    let (s_owned, writable_flag) = handle_chunks(py, s, allow_rechunk)?;
88    let array = series_to_numpy_view_recursive(py, s_owned, writable_flag);
89    Some((array, writable_flag))
90}
91
92/// Rechunk the Series if required.
93///
94/// NumPy arrays are always contiguous, so we may have to rechunk before creating a view.
95/// If we do so, we can flag the resulting array as writable.
96fn handle_chunks(py: Python<'_>, s: &Series, allow_rechunk: bool) -> Option<(Series, bool)> {
97    let is_chunked = s.n_chunks() > 1;
98    match (is_chunked, allow_rechunk) {
99        (true, false) => None,
100        (true, true) => Some((py.detach(|| s.rechunk()), true)),
101        (false, _) => Some((s.clone(), false)),
102    }
103}
104
105/// Create a NumPy view of the given Series without checking for data types, chunks, or nulls.
106fn series_to_numpy_view_recursive(py: Python<'_>, s: Series, writable: bool) -> Py<PyAny> {
107    debug_assert!(s.n_chunks() == 1);
108    match s.dtype() {
109        dt if dt.is_primitive_numeric() => numeric_series_to_numpy_view(py, s, writable),
110        DataType::Datetime(_, _) | DataType::Duration(_) => {
111            temporal_series_to_numpy_view(py, s, writable)
112        },
113        DataType::Array(_, _) => array_series_to_numpy_view(py, &s, writable),
114        _ => panic!("invalid data type"),
115    }
116}
117
118/// Create a NumPy view of a numeric Series.
119fn numeric_series_to_numpy_view(py: Python<'_>, s: Series, writable: bool) -> Py<PyAny> {
120    let dims = [s.len()].into_dimension();
121    with_match_physical_numpy_polars_type!(s.dtype(), |$T| {
122        let np_dtype = <$T as PolarsNumericType>::Native::get_dtype(py);
123        let ca: &ChunkedArray<$T> = s.unpack::<$T>().unwrap();
124        let flags = if writable {
125            flags::NPY_ARRAY_FARRAY
126        } else {
127            flags::NPY_ARRAY_FARRAY_RO
128        };
129
130        let slice = ca.data_views().next().unwrap();
131
132        unsafe {
133            create_borrowed_np_array::<_>(
134                py,
135                np_dtype,
136                dims,
137                flags,
138                slice.as_ptr() as _,
139                PySeries::from(s).into_py_any(py).unwrap(), // Keep the Series memory alive.,
140            )
141        }
142    })
143}
144
145/// Create a NumPy view of a Datetime or Duration Series.
146fn temporal_series_to_numpy_view(py: Python<'_>, s: Series, writable: bool) -> Py<PyAny> {
147    let np_dtype = polars_dtype_to_np_temporal_dtype(py, s.dtype());
148
149    let phys = s.to_physical_repr();
150    let ca = phys.i64().unwrap();
151    let slice = ca.data_views().next().unwrap();
152    let dims = [s.len()].into_dimension();
153    let flags = if writable {
154        flags::NPY_ARRAY_FARRAY
155    } else {
156        flags::NPY_ARRAY_FARRAY_RO
157    };
158
159    unsafe {
160        create_borrowed_np_array::<_>(
161            py,
162            np_dtype,
163            dims,
164            flags,
165            slice.as_ptr() as _,
166            PySeries::from(s).into_py_any(py).unwrap(), // Keep the Series memory alive.,
167        )
168    }
169}
170
171/// Create a NumPy view of an Array Series.
172fn array_series_to_numpy_view(py: Python<'_>, s: &Series, writable: bool) -> Py<PyAny> {
173    let ca = s.array().unwrap();
174    let s_inner = ca.get_inner();
175    let np_array_flat = series_to_numpy_view_recursive(py, s_inner, writable);
176
177    // Reshape to the original shape.
178    let DataType::Array(_, width) = s.dtype() else {
179        unreachable!()
180    };
181    reshape_numpy_array(py, np_array_flat, ca.len(), *width).unwrap()
182}
183
184/// Convert a Series to a NumPy ndarray, copying data in the process.
185///
186/// This method will cast integers to floats so that `null = np.nan`.
187fn series_to_numpy_with_copy(py: Python<'_>, s: &Series, writable: bool) -> Py<PyAny> {
188    use DataType::*;
189    match s.dtype() {
190        Int8 => numeric_series_to_numpy::<Int8Type, f32>(py, s),
191        Int16 => numeric_series_to_numpy::<Int16Type, f32>(py, s),
192        Int32 => numeric_series_to_numpy::<Int32Type, f64>(py, s),
193        Int64 => numeric_series_to_numpy::<Int64Type, f64>(py, s),
194        Int128 => {
195            let s = s.cast(&DataType::Float64).unwrap();
196            series_to_numpy(py, &s, writable, true).unwrap()
197        },
198        UInt8 => numeric_series_to_numpy::<UInt8Type, f32>(py, s),
199        UInt16 => numeric_series_to_numpy::<UInt16Type, f32>(py, s),
200        UInt32 => numeric_series_to_numpy::<UInt32Type, f64>(py, s),
201        UInt64 => numeric_series_to_numpy::<UInt64Type, f64>(py, s),
202        UInt128 => {
203            let s = s.cast(&DataType::Float64).unwrap();
204            series_to_numpy(py, &s, writable, true).unwrap()
205        },
206        Float32 => numeric_series_to_numpy::<Float32Type, f32>(py, s),
207        Float64 => numeric_series_to_numpy::<Float64Type, f64>(py, s),
208        Boolean => boolean_series_to_numpy(py, s),
209        Date => date_series_to_numpy(py, s),
210        Datetime(tu, _) => {
211            use numpy::datetime::{Datetime, units};
212            match tu {
213                TimeUnit::Milliseconds => {
214                    temporal_series_to_numpy::<Datetime<units::Milliseconds>>(py, s)
215                },
216                TimeUnit::Microseconds => {
217                    temporal_series_to_numpy::<Datetime<units::Microseconds>>(py, s)
218                },
219                TimeUnit::Nanoseconds => {
220                    temporal_series_to_numpy::<Datetime<units::Nanoseconds>>(py, s)
221                },
222            }
223        },
224        Duration(tu) => {
225            use numpy::datetime::{Timedelta, units};
226            match tu {
227                TimeUnit::Milliseconds => {
228                    temporal_series_to_numpy::<Timedelta<units::Milliseconds>>(py, s)
229                },
230                TimeUnit::Microseconds => {
231                    temporal_series_to_numpy::<Timedelta<units::Microseconds>>(py, s)
232                },
233                TimeUnit::Nanoseconds => {
234                    temporal_series_to_numpy::<Timedelta<units::Nanoseconds>>(py, s)
235                },
236            }
237        },
238        Time => {
239            let ca = s.time().unwrap();
240            let values = time_to_pyobject_iter(ca).map(|v| v.into_py_any(py).unwrap());
241            PyArray1::from_iter(py, values).into_py_any(py).unwrap()
242        },
243        String => {
244            let ca = s.str().unwrap();
245            let values = ca.iter().map(|s| s.into_py_any(py).unwrap());
246            PyArray1::from_iter(py, values).into_py_any(py).unwrap()
247        },
248        Binary => {
249            let ca = s.binary().unwrap();
250            let values = ca.iter().map(|s| s.into_py_any(py).unwrap());
251            PyArray1::from_iter(py, values).into_py_any(py).unwrap()
252        },
253        Categorical(_, _) | Enum(_, _) => {
254            with_match_categorical_physical_type!(s.dtype().cat_physical().unwrap(), |$C| {
255                let ca = s.cat::<$C>().unwrap();
256                let values = ca.iter_str().map(|s| s.into_py_any(py).unwrap());
257                PyArray1::from_iter(py, values).into_py_any(py).unwrap()
258            })
259        },
260        Decimal(_, _) => {
261            let ca = s.decimal().unwrap();
262            let values = decimal_to_pyobject_iter(py, ca)
263                .unwrap()
264                .map(|v| v.into_py_any(py).unwrap());
265            PyArray1::from_iter(py, values).into_py_any(py).unwrap()
266        },
267        List(_) => list_series_to_numpy(py, s, writable),
268        Array(_, _) => array_series_to_numpy(py, s, writable),
269        Struct(_) => {
270            let ca = s.struct_().unwrap();
271            let df = ca.clone().unnest();
272            df_to_numpy(py, &df, IndexOrder::Fortran, writable, true).unwrap()
273        },
274        #[cfg(feature = "object")]
275        Object(_) => {
276            let ca = s
277                .as_any()
278                .downcast_ref::<ObjectChunked<ObjectValue>>()
279                .unwrap();
280            let values = ca.iter().map(|v| v.into_py_any(py).unwrap());
281            PyArray1::from_iter(py, values).into_py_any(py).unwrap()
282        },
283        Null => {
284            let n = s.len();
285            let values = std::iter::repeat_n(f32::NAN, n);
286            PyArray1::from_iter(py, values).into_py_any(py).unwrap()
287        },
288        Unknown(_) | BinaryOffset => unreachable!(),
289    }
290}
291
292/// Convert numeric types to f32 or f64 with NaN representing a null value.
293fn numeric_series_to_numpy<T, U>(py: Python<'_>, s: &Series) -> Py<PyAny>
294where
295    T: PolarsNumericType,
296    T::Native: numpy::Element,
297    U: Float + numpy::Element,
298{
299    let ca: &ChunkedArray<T> = s.as_ref().as_ref();
300    if s.null_count() == 0 {
301        let values = ca.into_no_null_iter();
302        PyArray1::<T::Native>::from_iter(py, values)
303            .into_py_any(py)
304            .unwrap()
305    } else {
306        let mapper = |opt_v: Option<T::Native>| match opt_v {
307            Some(v) => NumCast::from(v).unwrap(),
308            None => U::nan(),
309        };
310        let values = ca.iter().map(mapper);
311        PyArray1::from_iter(py, values).into_py_any(py).unwrap()
312    }
313}
314
315/// Convert booleans to u8 if no nulls are present, otherwise convert to objects.
316fn boolean_series_to_numpy(py: Python<'_>, s: &Series) -> Py<PyAny> {
317    let ca = s.bool().unwrap();
318    if s.null_count() == 0 {
319        let values = ca.into_no_null_iter();
320        PyArray1::<bool>::from_iter(py, values)
321            .into_py_any(py)
322            .unwrap()
323    } else {
324        let values = ca.iter().map(|opt_v| opt_v.into_py_any(py).unwrap());
325        PyArray1::from_iter(py, values).into_py_any(py).unwrap()
326    }
327}
328
329/// Convert dates directly to i64 with i64::MIN representing a null value.
330fn date_series_to_numpy(py: Python<'_>, s: &Series) -> Py<PyAny> {
331    use numpy::datetime::{Datetime, units};
332
333    let s_phys = s.to_physical_repr();
334    let ca = s_phys.i32().unwrap();
335
336    if s.null_count() == 0 {
337        let mapper = |v: i32| (v as i64).into();
338        let values = ca.into_no_null_iter().map(mapper);
339        PyArray1::<Datetime<units::Days>>::from_iter(py, values)
340            .into_py_any(py)
341            .unwrap()
342    } else {
343        let mapper = |opt_v: Option<i32>| {
344            match opt_v {
345                Some(v) => v as i64,
346                None => i64::MIN,
347            }
348            .into()
349        };
350        let values = ca.iter().map(mapper);
351        PyArray1::<Datetime<units::Days>>::from_iter(py, values)
352            .into_py_any(py)
353            .unwrap()
354    }
355}
356
357/// Convert datetimes and durations with i64::MIN representing a null value.
358fn temporal_series_to_numpy<T>(py: Python<'_>, s: &Series) -> Py<PyAny>
359where
360    T: From<i64> + numpy::Element,
361{
362    let s_phys = s.to_physical_repr();
363    let ca = s_phys.i64().unwrap();
364    let values = ca.iter().map(|v| v.unwrap_or(i64::MIN).into());
365    PyArray1::<T>::from_iter(py, values)
366        .into_py_any(py)
367        .unwrap()
368}
369fn list_series_to_numpy(py: Python<'_>, s: &Series, writable: bool) -> Py<PyAny> {
370    let ca = s.list().unwrap();
371
372    let iter = ca.amortized_iter().map(|opt_s| match opt_s {
373        None => py.None(),
374        Some(s) => series_to_numpy(py, s.as_ref(), writable, true).unwrap(),
375    });
376    PyArray1::from_iter(py, iter).into_py_any(py).unwrap()
377}
378
379/// Convert arrays by flattening first, converting the flat Series, and then reshaping.
380fn array_series_to_numpy(py: Python<'_>, s: &Series, writable: bool) -> Py<PyAny> {
381    let ca = s.array().unwrap();
382    let s_inner = ca.get_inner();
383    let np_array_flat = series_to_numpy_with_copy(py, &s_inner, writable);
384
385    // Reshape to the original shape.
386    let DataType::Array(_, width) = s.dtype() else {
387        unreachable!()
388    };
389    reshape_numpy_array(py, np_array_flat, ca.len(), *width).unwrap()
390}
polars_python/interop/numpy/to_numpy_series.rs

polars_python/interop/numpy/
to_numpy_series.rs
