Fraction serialization in Python mode

benches/main.rs

@@ -151,7 +151,6 @@ fn list_error_json(bench: &mut Bencher) {
             Ok(_) => panic!("unexpectedly valid"),
             Err(e) => {
                 let v = e.value(py);
-                // println!("error: {}", v.to_string());
                 assert_eq!(v.getattr("title").unwrap().to_string(), "list[int]");
                 let error_count: i64 = v.call_method0("error_count").unwrap().extract().unwrap();
                 assert_eq!(error_count, 100);
@@ -184,7 +183,6 @@ fn list_error_python_input(py: Python<'_>) -> (SchemaValidator, PyObject) {
         Ok(_) => panic!("unexpectedly valid"),
         Err(e) => {
             let v = e.value(py);
-            // println!("error: {}", v.to_string());
             assert_eq!(v.getattr("title").unwrap().to_string(), "list[int]");
             let error_count: i64 = v.call_method0("error_count").unwrap().extract().unwrap();
             assert_eq!(error_count, 100);
@@ -357,7 +355,6 @@ fn dict_value_error(bench: &mut Bencher) {
             Ok(_) => panic!("unexpectedly valid"),
             Err(e) => {
                 let v = e.value(py);
-                // println!("error: {}", v.to_string());
                 assert_eq!(v.getattr("title").unwrap().to_string(), "dict[str,constrained-int]");
                 let error_count: i64 = v.call_method0("error_count").unwrap().extract().unwrap();
                 assert_eq!(error_count, 100);
@@ -484,7 +481,6 @@ fn typed_dict_deep_error(bench: &mut Bencher) {
             Ok(_) => panic!("unexpectedly valid"),
             Err(e) => {
                 let v = e.value(py);
-                // println!("error: {}", v.to_string());
                 assert_eq!(v.getattr("title").unwrap().to_string(), "typed-dict");
                 let error_count: i64 = v.call_method0("error_count").unwrap().extract().unwrap();
                 assert_eq!(error_count, 1);

python/pydantic_core/core_schema.py

@@ -10,6 +10,7 @@
 from collections.abc import Hashable, Mapping
 from datetime import date, datetime, time, timedelta
 from decimal import Decimal
+from fractions import Fraction
 from re import Pattern
 from typing import TYPE_CHECKING, Any, Callable, Literal, Union
 
@@ -809,6 +810,61 @@ def decimal_schema(
         serialization=serialization,
     )
 
+class FractionSchema(TypedDict, total=False):
+    type: Required[Literal['decimal']]
+    le: Decimal
+    ge: Decimal
+    lt: Decimal
+    gt: Decimal
+    strict: bool
+    ref: str
+    metadata: dict[str, Any]
+    serialization: SerSchema
+
+def fraction_schema(
+    *,
+    le: Fraction | None = None,
+    ge: Fraction | None = None,
+    lt: Fraction | None = None,
+    gt: Fraction | None = None,
+    strict: bool | None = None,
+    ref: str | None = None,
+    metadata: dict[str, Any] | None = None,
+    serialization: SerSchema | None = None,
+) -> FractionSchema:
+    """
+    Returns a schema that matches a fraction value, e.g.:
+
+    ```py
+    from fractions import Fraction
+    from pydantic_core import SchemaValidator, core_schema
+
+    schema = core_schema.fraction_schema(le=0.8, ge=0.2)
+    v = SchemaValidator(schema)
+    assert v.validate_python(1, 2) == Fraction(1, 2)
+    ```
+
+    Args:
+        le: The value must be less than or equal to this number
+        ge: The value must be greater than or equal to this number
+        lt: The value must be strictly less than this number
+        gt: The value must be strictly greater than this number
+        strict: Whether the value should be a float or a value that can be converted to a float
+        ref: optional unique identifier of the schema, used to reference the schema in other places
+        metadata: Any other information you want to include with the schema, not used by pydantic-core
+        serialization: Custom serialization schema
+    """
+    return _dict_not_none(
+        type='fraction',
+        gt=gt,
+        ge=ge,
+        lt=lt,
+        le=le,
+        strict=strict,
+        ref=ref,
+        metadata=metadata,
+        serialization=serialization,
+    )
 
 class ComplexSchema(TypedDict, total=False):
     type: Required[Literal['complex']]
@@ -4109,6 +4165,7 @@ def definition_reference_schema(
         IntSchema,
         FloatSchema,
         DecimalSchema,
+        FractionSchema,
         StringSchema,
         BytesSchema,
         DateSchema,
@@ -4168,6 +4225,7 @@ def definition_reference_schema(
     'int',
     'float',
     'decimal',
+    'fraction',
     'str',
     'bytes',
     'date',
@@ -4318,6 +4376,8 @@ def definition_reference_schema(
     'uuid_version',
     'decimal_type',
     'decimal_parsing',
+    'fraction_type',
+    'fraction_parsing',
     'decimal_max_digits',
     'decimal_max_places',
     'decimal_whole_digits',

src/errors/types.rs

@@ -430,6 +430,9 @@ error_types! {
     DecimalWholeDigits {
         whole_digits: {ctx_type: u64, ctx_fn: field_from_context},
     },
+    // Fraction errors
+    FractionType {},
+    FractionParsing {},
     // Complex errors
     ComplexType {},
     ComplexStrParsing {},
@@ -579,6 +582,8 @@ impl ErrorType {
             Self::DecimalMaxDigits {..} => "Decimal input should have no more than {max_digits} digit{expected_plural} in total",
             Self::DecimalMaxPlaces {..} => "Decimal input should have no more than {decimal_places} decimal place{expected_plural}",
             Self::DecimalWholeDigits {..} => "Decimal input should have no more than {whole_digits} digit{expected_plural} before the decimal point",
+            Self::FractionParsing {..} => "Fraction input should be a tuple of two integers, a string or a Fraction object",
+            Self::FractionType {..} => "Fraction input should be a tuple of two integers, or a string or Fraction object",
             Self::ComplexType {..} => "Input should be a valid python complex object, a number, or a valid complex string following the rules at https://docs.python.org/3/library/functions.html#complex",
             Self::ComplexStrParsing {..} => "Input should be a valid complex string following the rules at https://docs.python.org/3/library/functions.html#complex",
         }

src/input/input_abstract.rs

@@ -115,6 +115,8 @@ pub trait Input<'py>: fmt::Debug {
 
     fn validate_decimal(&self, strict: bool, py: Python<'py>) -> ValMatch<Bound<'py, PyAny>>;
 
+    fn validate_fraction(&self, strict: bool, py: Python<'py>) -> ValMatch<Bound<'py, PyAny>>;
+
     type Dict<'a>: ValidatedDict<'py>
     where
         Self: 'a;

src/input/input_json.rs

@@ -12,6 +12,7 @@ use crate::input::return_enums::EitherComplex;
 use crate::lookup_key::{LookupKey, LookupPath};
 use crate::validators::complex::string_to_complex;
 use crate::validators::decimal::create_decimal;
+use crate::validators::fraction::create_fraction;
 use crate::validators::{TemporalUnitMode, ValBytesMode};
 
 use super::datetime::{
@@ -199,6 +200,15 @@ impl<'py, 'data> Input<'py> for JsonValue<'data> {
         }
     }
 
+    fn validate_fraction(&self, _strict: bool, py: Python<'py>) -> ValMatch<Bound<'py, PyAny>> {
+        match self {
+            JsonValue::Str(..) | JsonValue::Int(..) | JsonValue::BigInt(..) => {
+                create_fraction(&self.into_pyobject(py)?, self).map(ValidationMatch::strict)
+            }
+            _ => Err(ValError::new(ErrorTypeDefaults::DecimalType, self)),
+        }
+    }
+
     type Dict<'a>
         = &'a JsonObject<'data>
     where
@@ -454,6 +464,10 @@ impl<'py> Input<'py> for str {
         create_decimal(self.into_pyobject(py)?.as_any(), self).map(ValidationMatch::lax)
     }
 
+    fn validate_fraction(&self, _strict: bool, py: Python<'py>) -> ValMatch<Bound<'py, PyAny>> {
+        create_fraction(self.into_pyobject(py)?.as_any(), self).map(ValidationMatch::lax)
+    }
+
     type Dict<'a> = Never;
 
     #[cfg_attr(has_coverage_attribute, coverage(off))]

src/input/input_python.rs

@@ -3,7 +3,6 @@ use std::str::from_utf8;
 use pyo3::intern;
 use pyo3::prelude::*;
 
-use pyo3::sync::PyOnceLock;
 use pyo3::types::PyType;
 use pyo3::types::{
     PyBool, PyByteArray, PyBytes, PyComplex, PyDate, PyDateTime, PyDict, PyFloat, PyFrozenSet, PyInt, PyIterator,
@@ -18,6 +17,7 @@ use crate::errors::{ErrorType, ErrorTypeDefaults, InputValue, LocItem, ValError,
 use crate::tools::{extract_i64, safe_repr};
 use crate::validators::complex::string_to_complex;
 use crate::validators::decimal::{create_decimal, get_decimal_type};
+use crate::validators::fraction::{create_fraction, get_fraction_type};
 use crate::validators::Exactness;
 use crate::validators::TemporalUnitMode;
 use crate::validators::ValBytesMode;
@@ -48,20 +48,6 @@ use super::{
     Input,
 };
 
-static FRACTION_TYPE: PyOnceLock<Py<PyType>> = PyOnceLock::new();
-
-pub fn get_fraction_type(py: Python<'_>) -> &Bound<'_, PyType> {
-    FRACTION_TYPE
-        .get_or_init(py, || {
-            py.import("fractions")
-                .and_then(|fractions_module| fractions_module.getattr("Fraction"))
-                .unwrap()
-                .extract()
-                .unwrap()
-        })
-        .bind(py)
-}
-
 pub(crate) fn downcast_python_input<'py, T: PyTypeCheck>(input: &(impl Input<'py> + ?Sized)) -> Option<&Bound<'py, T>> {
     input.as_python().and_then(|any| any.downcast::<T>().ok())
 }
@@ -290,8 +276,8 @@ impl<'py> Input<'py> for Bound<'py, PyAny> {
                     float_as_int(self, self.extract::<f64>()?)
                 } else if let Ok(decimal) = self.validate_decimal(true, self.py()) {
                     decimal_as_int(self, &decimal.into_inner())
-                } else if self.is_instance(get_fraction_type(self.py()))? {
-                    fraction_as_int(self)
+                } else if let Ok(fraction) = self.validate_fraction(true, self.py()) {
+                    fraction_as_int(self, &fraction.into_inner())
                 } else if let Ok(float) = self.extract::<f64>() {
                     float_as_int(self, float)
                 } else if let Some(enum_val) = maybe_as_enum(self) {
@@ -349,6 +335,33 @@ impl<'py> Input<'py> for Bound<'py, PyAny> {
         Err(ValError::new(ErrorTypeDefaults::FloatType, self))
     }
 
+    fn validate_fraction(&self, strict: bool, py: Python<'py>) -> ValMatch<Bound<'py, PyAny>> {
+        let fraction_type = get_fraction_type(py);
+
+        // Fast path for existing decimal objects
+        if self.is_exact_instance(fraction_type) {
+            return Ok(ValidationMatch::exact(self.to_owned().clone()));
+        }
+
+        if !strict && self.is_instance_of::<PyString>() {
+            return create_fraction(self, self).map(ValidationMatch::lax);
+        }
+
+        let error_type = if strict {
+            ErrorType::IsInstanceOf {
+                class: fraction_type
+                    .qualname()
+                    .and_then(|name| name.extract())
+                    .unwrap_or_else(|_| "Fraction".to_owned()),
+                context: None,
+            }
+        } else {
+            ErrorTypeDefaults::FractionType
+        };
+
+        Err(ValError::new(error_type, self))
+    }
+
     fn validate_decimal(&self, strict: bool, py: Python<'py>) -> ValMatch<Bound<'py, PyAny>> {
         let decimal_type = get_decimal_type(py);
 

src/input/input_string.rs

@@ -9,6 +9,7 @@ use crate::lookup_key::{LookupKey, LookupPath};
 use crate::tools::safe_repr;
 use crate::validators::complex::string_to_complex;
 use crate::validators::decimal::create_decimal;
+use crate::validators::fraction::create_fraction;
 use crate::validators::{TemporalUnitMode, ValBytesMode};
 
 use super::datetime::{
@@ -154,6 +155,13 @@ impl<'py> Input<'py> for StringMapping<'py> {
         }
     }
 
+    fn validate_fraction(&self, _strict: bool, _py: Python<'py>) -> ValMatch<Bound<'py, PyAny>> {
+        match self {
+            Self::String(s) => create_fraction(s, self).map(ValidationMatch::strict),
+            Self::Mapping(_) => Err(ValError::new(ErrorTypeDefaults::DecimalType, self)),
+        }
+    }
+
     type Dict<'a>
         = StringMappingDict<'py>
     where

src/input/shared.rs

@@ -228,22 +228,18 @@ pub fn decimal_as_int<'py>(
     Ok(EitherInt::Py(numerator))
 }
 
-pub fn fraction_as_int<'py>(input: &Bound<'py, PyAny>) -> ValResult<EitherInt<'py>> {
-    #[cfg(Py_3_12)]
-    let is_integer = input.call_method0("is_integer")?.extract::<bool>()?;
-    #[cfg(not(Py_3_12))]
-    let is_integer = input.getattr("denominator")?.extract::<i64>().map_or(false, |d| d == 1);
-
-    if is_integer {
-        #[cfg(Py_3_11)]
-        let as_int = input.call_method0("__int__");
-        #[cfg(not(Py_3_11))]
-        let as_int = input.call_method0("__trunc__");
-        match as_int {
-            Ok(i) => Ok(EitherInt::Py(i.as_any().to_owned())),
-            Err(_) => Err(ValError::new(ErrorTypeDefaults::IntType, input)),
-        }
-    } else {
-        Err(ValError::new(ErrorTypeDefaults::IntFromFloat, input))
+pub fn fraction_as_int<'py>(
+    input: &(impl Input<'py> + ?Sized),
+    fraction: &Bound<'py, PyAny>,
+) -> ValResult<EitherInt<'py>> {
+    let py = fraction.py();
+
+    // as_integer_ratio was added in Python 3.8, so this should be fine
+    let (numerator, denominator) = fraction
+        .call_method0(intern!(py, "as_integer_ratio"))?
+        .extract::<(Bound<'_, PyAny>, Bound<'_, PyAny>)>()?;
+    if denominator.extract::<i64>().map_or(true, |d| d != 1) {
+        return Err(ValError::new(ErrorTypeDefaults::IntFromFloat, input));
     }
+    Ok(EitherInt::Py(numerator))
 }

src/serializers/infer.rs

@@ -137,6 +137,7 @@ pub(crate) fn infer_to_python_known(
                 v.into_py_any(py)?
             }
             ObType::Decimal => value.to_string().into_py_any(py)?,
+            ObType::Fraction => value.to_string().into_py_any(py)?,
             ObType::StrSubclass => PyString::new(py, value.downcast::<PyString>()?.to_str()?).into(),
             ObType::Bytes => extra
                 .config
@@ -431,6 +432,7 @@ pub(crate) fn infer_serialize_known<S: Serializer>(
             type_serializers::float::serialize_f64(v, serializer, extra.config.inf_nan_mode)
         }
         ObType::Decimal => value.to_string().serialize(serializer),
+        ObType::Fraction => value.to_string().serialize(serializer),
         ObType::Str | ObType::StrSubclass => {
             let py_str = value.downcast::<PyString>().map_err(py_err_se_err)?;
             super::type_serializers::string::serialize_py_str(py_str, serializer)
@@ -613,6 +615,7 @@ pub(crate) fn infer_json_key_known<'a>(
             }
         }
         ObType::Decimal => Ok(Cow::Owned(key.to_string())),
+        ObType::Fraction => Ok(Cow::Owned(key.to_string())),
         ObType::Bool => super::type_serializers::simple::bool_json_key(key),
         ObType::Str | ObType::StrSubclass => key.downcast::<PyString>()?.to_cow(),
         ObType::Bytes => extra