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title Configuration
sidebar_position 4
id configuration
license Licensed to the Apache Software Foundation (ASF) under one or more contributor license agreements. See the NOTICE file distributed with this work for additional information regarding copyright ownership. The ASF licenses this file to You under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0 Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

This page covers Python Fory instance configuration. pyfory.Fory() defaults to xlang mode with compatible schema evolution. Native mode is selected explicitly with xlang=False and also defaults to compatible schema evolution.

Fory Class

The main serialization interface:

class Fory:
    def __init__(
        self,
        xlang: bool = True,
        ref: bool = False,
        strict: bool = True,
        compatible: Optional[bool] = None,
        max_depth: int = 50,
        policy: DeserializationPolicy = None,
        field_nullable: bool = False,
        meta_compressor=None,
    )

ThreadSafeFory Class

Thread-safe serialization interface using a pooled wrapper:

class ThreadSafeFory:
    def __init__(
        self, fory_factory=None, **kwargs
    )

Parameters

Parameter Type Default Description
xlang bool True Use xlang mode. Set False for Python native mode.
ref bool False Enable reference tracking for shared/circular references. Disable for better performance if your data has no shared references.
strict bool True Require type registration for security. Keep this enabled for production unless a policy owns trust decisions.
compatible bool | None None Schema evolution mode. None enables compatible mode in both xlang and native mode. Set False only when every reader and writer uses the same schema.
max_depth int 50 Maximum deserialization depth for security, preventing stack overflow attacks.
policy DeserializationPolicy | None None Deserialization policy used for security checks. Strongly recommended when strict=False.
field_nullable bool False Treat dataclass fields as nullable by default.
meta_compressor Any None Optional metadata compressor used for compatible-mode metadata encoding.
fory_factory Callable | None None ThreadSafeFory factory hook. When set, ThreadSafeFory creates instances via this callback; otherwise it forwards **kwargs to Fory construction.

Key Methods

# Serialization (serialize/deserialize are identical to dumps/loads)
data: bytes = fory.serialize(obj)
obj = fory.deserialize(data)

# Alternative API (aliases)
data: bytes = fory.dumps(obj)
obj = fory.loads(data)

# Type registration by id
fory.register(MyClass, type_id=123)
fory.register(MyClass, type_id=123, serializer=custom_serializer)

# Type registration by name
fory.register(MyClass, name="my.package.MyClass")
fory.register(MyClass, name="my.package.MyClass", serializer=custom_serializer)

Xlang And Native Mode Comparison

Feature Native mode (xlang=False) Xlang mode (default)
Use case Python-only applications Multi-language systems
Compatibility Python only Java, C++, Go, Rust, JavaScript/TypeScript, C#, Swift, Dart, Scala, Kotlin, etc.
Supported types Python object surface Cross-language compatible types
Functions/lambdas Supported with trusted dynamic deserialization Not allowed
Local classes Supported with trusted dynamic deserialization Not allowed
Dynamic classes Supported with trusted dynamic deserialization Not allowed
Schema mode default Compatible Compatible

Xlang Mode

Xlang mode is the default and restricts payloads to types compatible across Fory implementations:

import pyfory

fory = pyfory.Fory(xlang=True, ref=True)
fory.register(MyDataClass, name="com.example.MyDataClass")
data = fory.serialize(MyDataClass(field1="value", field2=42))

Use compatible=False for xlang payloads only when every reader and writer always uses the same schema and you want faster serialization and smaller size. Use it only after verifying that every language uses that schema, or when native types are generated from Fory schema IDL.

Native Mode

import pyfory

fory = pyfory.Fory(xlang=False, ref=True, strict=False)

Native mode supports Python-specific object features such as functions, local classes, methods, __reduce__, and __getstate__. Compatible mode is still enabled by default. Set compatible=False only when every reader and writer always uses the same Python class schema and you want faster serialization and smaller size.

Compatible Mode

Compatible mode is enabled by default for both xlang and native mode. Keep this default when Python classes may evolve independently, when services deploy separately, or when xlang schemas are written by hand in different languages.

For xlang payloads, set compatible=False only after verifying that every language uses the same schema, or when native types are generated from Fory schema IDL.

Example Configurations

Xlang Service

import pyfory

fory = pyfory.Fory(
    xlang=True,
    ref=False,
    strict=True,
    max_depth=20,
)

fory.register(UserModel, name="example.User")

Native Mode With Dynamic Types

import pyfory

fory = pyfory.Fory(
    xlang=False,
    ref=True,
    strict=False,
    max_depth=1000,
)

Use strict=False only for trusted data, preferably with a policy= deserialization policy.

Security

Treat native-mode bytes from untrusted sources the same way you would treat untrusted pickle bytes. Native mode can reconstruct Python objects, import modules, invoke reduction hooks, and rebuild dynamic classes or functions when strict=False.

Production Configuration

Keep strict=True for production payloads unless the whole data source is trusted and a DeserializationPolicy owns the remaining trust decisions:

import pyfory

fory = pyfory.Fory(
    xlang=True,
    ref=False,
    strict=True,
    max_depth=50,
)

fory.register(UserModel, name="example.User")
fory.register(OrderModel, name="example.Order")

Use dynamic native-mode deserialization (strict=False) only for trusted Python-only payloads:

import pyfory

fory = pyfory.Fory(
    xlang=False,
    ref=True,
    strict=False,
    max_depth=100,
)

DeserializationPolicy

When strict=False is necessary, use DeserializationPolicy to restrict the dynamic types and hooks accepted during deserialization:

import pyfory
from pyfory import DeserializationPolicy

dangerous_modules = {"subprocess", "os", "__builtin__"}

class SafeDeserializationPolicy(DeserializationPolicy):
    def validate_class(self, cls, is_local, **kwargs):
        if cls.__module__ in dangerous_modules:
            raise ValueError(f"Blocked dangerous class: {cls.__module__}.{cls.__name__}")

    def intercept_reduce_call(self, callable_obj, args, **kwargs):
        if getattr(callable_obj, "__name__", "") == "Popen":
            raise ValueError("Blocked attempt to invoke subprocess.Popen")
        return None

    def intercept_setstate(self, obj, state, **kwargs):
        if isinstance(state, dict) and "password" in state:
            state["password"] = "***REDACTED***"
        return None

policy = SafeDeserializationPolicy()
fory = pyfory.Fory(xlang=False, ref=True, strict=False, policy=policy)

Available policy hooks include:

Reference validation hooks reject by raising exceptions and otherwise leave deserialized references unchanged.

Hook Description
validate_class(cls, is_local) Validate or block class types
validate_module(module_name, is_local) Validate or block module imports
validate_function(func, is_local) Validate or block function references
validate_method(method, is_local) Validate or block method references
intercept_reduce_call(callable_obj, args) Intercept __reduce__ invocations
inspect_reduced_object(obj) Inspect or replace objects created via __reduce__
intercept_setstate(obj, state) Sanitize state before __setstate__
authorize_instantiation(cls, args, kwargs) Control class instantiation

Security Checklist

  • Keep strict=True for untrusted data.
  • Register all expected application types before deserialization.
  • Use DeserializationPolicy when strict=False is necessary.
  • Keep max_depth low enough to reject unexpectedly deep payloads.
  • Do not treat xlang/native mode choice as a security control.

Related Topics