Add DataFrame.deserialize

py-polars/polars/dataframe/frame.py

@@ -98,6 +98,7 @@
     TooManyRowsReturnedError,
 )
 from polars.functions import col, lit
+from polars.polars import PyDataFrame
 from polars.selectors import _expand_selector_dicts, _expand_selectors
 from polars.type_aliases import DbWriteMode, JaxExportType, TorchExportType
 
@@ -121,7 +122,6 @@
     from polars import DataType, Expr, LazyFrame, Series
     from polars.interchange.dataframe import PolarsDataFrame
     from polars.ml.torch import PolarsDataset
-    from polars.polars import PyDataFrame
     from polars.type_aliases import (
         AsofJoinStrategy,
         AvroCompression,
@@ -418,6 +418,46 @@ def __init__(
             )
             raise TypeError(msg)
 
+    @classmethod
+    def deserialize(cls, source: str | Path | IOBase) -> Self:
+        """
+        Read a serialized DataFrame from a file.
+
+        Parameters
+        ----------
+        source
+            Path to a file or a file-like object (by file-like object, we refer to
+            objects that have a `read()` method, such as a file handler (e.g.
+            via builtin `open` function) or `BytesIO`).
+
+        See Also
+        --------
+        DataFrame.serialize
+
+        Examples
+        --------
+        >>> import io
+        >>> df = pl.DataFrame({"a": [1, 2, 3], "b": [4.0, 5.0, 6.0]})
+        >>> json = df.serialize()
+        >>> pl.DataFrame.deserialize(io.StringIO(json))
+        shape: (3, 2)
+        ┌─────┬─────┐
+        │ a   ┆ b   │
+        │ --- ┆ --- │
+        │ i64 ┆ f64 │
+        ╞═════╪═════╡
+        │ 1   ┆ 4.0 │
+        │ 2   ┆ 5.0 │
+        │ 3   ┆ 6.0 │
+        └─────┴─────┘
+        """
+        if isinstance(source, StringIO):
+            source = BytesIO(source.getvalue().encode())
+        elif isinstance(source, (str, Path)):
+            source = normalize_filepath(source)
+
+        return cls._from_pydf(PyDataFrame.deserialize(source))
+
     @classmethod
     def _from_pydf(cls, py_df: PyDataFrame) -> Self:
         """Construct Polars DataFrame from FFI PyDataFrame object."""

py-polars/polars/expr/expr.py

@@ -340,7 +340,7 @@ def function(s: Series) -> Series:  # pragma: no cover
     @classmethod
     def deserialize(cls, source: str | Path | IOBase) -> Self:
         """
-        Read an expression from a JSON file.
+        Read a serialized expression from a file.
 
         Parameters
         ----------
@@ -351,10 +351,9 @@ def deserialize(cls, source: str | Path | IOBase) -> Self:
 
         Warnings
         --------
-            This function uses :mod:`pickle` under some circumstances, and as
-            such inherits the security implications. Deserializing can execute
-            arbitrary code so it should only be attempted on trusted data.
-            pickle is only used when the logical plan contains python UDFs.
+        This function uses :mod:`pickle` when the logical plan contains Python UDFs,
+        and as such inherits the security implications. Deserializing can execute
+        arbitrary code, so it should only be attempted on trusted data.
 
         See Also
         --------

py-polars/polars/lazyframe/frame.py

@@ -348,7 +348,7 @@ def _scan_python_function(
     @classmethod
     def deserialize(cls, source: str | Path | IOBase) -> Self:
         """
-        Read a logical plan from a JSON file to construct a LazyFrame.
+        Read a logical plan from a file to construct a LazyFrame.
 
         Parameters
         ----------
@@ -359,11 +359,9 @@ def deserialize(cls, source: str | Path | IOBase) -> Self:
 
         Warnings
         --------
-            This function uses :mod:`pickle` under some circumstances, and as
-            such inherits the security implications. Deserializing can execute
-            arbitrary code so it should only be attempted on trusted data.
-            pickle is only used when the logical plan contains python UDFs.
-
+        This function uses :mod:`pickle` when the logical plan contains Python UDFs,
+        and as such inherits the security implications. Deserializing can execute
+        arbitrary code, so it should only be attempted on trusted data.
 
         See Also
         --------

py-polars/src/dataframe/io.rs

@@ -183,6 +183,27 @@ impl PyDataFrame {
         Ok(PyDataFrame::new(df))
     }
 
+    #[staticmethod]
+    #[cfg(feature = "json")]
+    pub fn deserialize(py: Python, mut py_f: Bound<PyAny>) -> PyResult<Self> {
+        use crate::file::read_if_bytesio;
+        py_f = read_if_bytesio(py_f);
+        let mmap_bytes_r = get_mmap_bytes_reader(&py_f)?;
+
+        py.allow_threads(move || {
+            let mmap_read: ReaderBytes = (&mmap_bytes_r).into();
+            let bytes = mmap_read.deref();
+            match serde_json::from_slice::<DataFrame>(bytes) {
+                Ok(df) => Ok(df.into()),
+                Err(e) => {
+                    let msg = format!("{e}");
+                    let e = PyPolarsErr::from(PolarsError::ComputeError(msg.into()));
+                    Err(PyErr::from(e))
+                },
+            }
+        })
+    }
+
     #[staticmethod]
     #[cfg(feature = "json")]
     pub fn read_json(