fix(python): Correctly parse special float values in from_repr (#20351

)

py-polars/polars/_utils/various.py

@@ -297,6 +297,8 @@ def _cast_repr_strings_with_schema(
                 msg = f"DataFrame should contain only String repr data; found {tp!r}"
                 raise TypeError(msg)
 
+    special_floats = {"-inf", "+inf", "inf", "nan"}
+
     # duration string scaling
     ns_sec = 1_000_000_000
     duration_scaling = {
@@ -366,8 +368,11 @@ def str_duration_(td: str | None) -> int | None:
                 integer_part = F.col(c).str.replace(r"^(.*)\D(\d*)$", "$1")
                 fractional_part = F.col(c).str.replace(r"^(.*)\D(\d*)$", "$2")
                 cast_cols[c] = (
-                    # check for empty string and/or integer format
-                    pl.when(F.col(c).str.contains(r"^[+-]?\d*$"))
+                    # check for empty string, special floats, or integer format
+                    pl.when(
+                        F.col(c).str.contains(r"^[+-]?\d*$")
+                        | F.col(c).str.to_lowercase().is_in(special_floats)
+                    )
                     .then(pl.when(F.col(c).str.len_bytes() > 0).then(F.col(c)))
                     # check for scientific notation
                     .when(F.col(c).str.contains("[eE]"))

py-polars/polars/convert/general.py

@@ -760,7 +760,12 @@ def _from_dataframe_repr(m: re.Match[str]) -> DataFrame:
                 buf = io.BytesIO()
                 df.write_csv(file=buf)
                 buf.seek(0)
-                df = read_csv(buf, new_columns=df.columns, try_parse_dates=True)
+                df = read_csv(
+                    buf,
+                    new_columns=df.columns,
+                    try_parse_dates=True,
+                    infer_schema_length=None,
+                )
             return df
     elif schema and not data:
         return df.cast(schema)  # type: ignore[arg-type]
@@ -786,8 +791,16 @@ def _from_series_repr(m: re.Match[str]) -> Series:
         ]
         if string_values == ["[", "]"]:
             string_values = []
-        elif string_values and string_values[0].lstrip("#> ") == "[":
-            string_values = string_values[1:]
+        else:
+            start: int | None = None
+            end: int | None = None
+            for idx, v in enumerate(string_values):
+                if start is None and v.lstrip("#> ") == "[":
+                    start = idx
+                if v.lstrip("#> ") == "]":
+                    end = idx
+            if start is not None and end is not None:
+                string_values = string_values[start + 1 : end]
 
     values = string_values[:length] if length > 0 else string_values
     values = [(None if v == "null" else v) for v in values if v not in ("…", "...")]

py-polars/tests/unit/interop/test_interop.py

@@ -616,6 +616,33 @@ def test_series_from_repr() -> None:
     )
     assert_series_equal(s, pl.Series("flt", [], dtype=pl.Float32))
 
+    s = cast(
+        pl.Series,
+        pl.from_repr(
+            """
+            Series: 'flt' [f64]
+            [
+                null
+                +inf
+                -inf
+                inf
+                0.0
+                NaN
+            ]
+            >>> print("stuff")
+            """
+        ),
+    )
+    inf, nan = float("inf"), float("nan")
+    assert_series_equal(
+        s,
+        pl.Series(
+            name="flt",
+            dtype=pl.Float64,
+            values=[None, inf, -inf, inf, 0.0, nan],
+        ),
+    )
+
 
 def test_dataframe_from_repr_custom_separators() -> None:
     # repr created with custom digit-grouping