> ## Documentation Index
> Fetch the complete documentation index at: https://developers.circle.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Server-side SDK Pydantic v2 upgrade

This guide provides information about the Pydantic v2 upgrade for the
Server-side Python SDKs for
[developer-controlled wallets](/sdks/developer-controlled-wallets-python-sdk),
[user-controlled wallets](/sdks/user-controlled-wallets-python-sdk), and
[Contracts](/sdks/contracts-python-sdk). Pydantic is a Python library for data
modeling and validation that uses type hints to enforce structure, parse input,
and serialize output.

As of version 9.0.0, the Server-side Circle SDKs are upgrading to Pydantic v2
because the new `pydantic-core` package is built with Rust and delivers
significant performance improvements, better correctness, and more consistent
classes, methods, decorators and settings.

## Migration guidance

If you are using the Circle Python SDK and don't want to migrate your code, you
should not upgrade your SDK version past major version 8. Version 8 is in
maintenance mode and will only receive essential updates such as fixes for
critical security flaws.

If you want to upgrade to major version 9 and above, you may need to make some
changes to your code. Review the following sections to see if you are affected.

## No impact

Unless noted in the following section, function signatures in the Python SDK are
unchanged, including:

* API methods
* Core features such as wallet creation and transaction processing

For example, the following usage is unaffected between versions 8 and 9 of the
SDK:

```python theme={null}
from circle.web3.developer_controlled_wallets.api.wallets_api import WalletsApi
from circle.web3.developer_controlled_wallets.models.create_wallet_request import CreateWalletRequest
from circle.web3.developer_controlled_wallets.models.blockchain import Blockchain
from circle.web3.developer_controlled_wallets.models.account_type import AccountType
# These patterns are NOT affected
api_instance = WalletsApi(api_client=client)
request = CreateWalletRequest(
      blockchains=[Blockchain.ETH_MINUS_SEPOLIA],
      wallet_set_id="550e8400-e29b-41d4-a716-446655440002",
      account_type=AccountType.SCA,
      count=1
  )
response = api_instance.create_wallet(request)
wallet_id = response.data.wallet.actual_instance.id
result = api_instance.get_wallet(id=wallet_id)
```

## Summary of changes

The method names of model serialization methods that convert between model
objects and data formats are changing to match the Pydantic v2 naming pattern.
Deserialization methods are typically used to build API request payloads, where
serialization methods are used to parse API responses:

* `model.from_dict()`: deserialize a Python dictionary into a model instance
* `model.from_json()`: deserialize a JSON string into a model instance
* `model.to_dict()`: serialize a model instance to a Python dictionary
* `model.to_json()`: serialize a model instance to a JSON string

The following example shows how to use the new model serialization methods:

```python theme={null}
from circle.web3.developer_controlled_wallets.models.eoa_wallet import EOAWallet
from circle.web3.developer_controlled_wallets.models.blockchain import Blockchain
from circle.web3.developer_controlled_wallets.models.custody_type import CustodyType
from circle.web3.developer_controlled_wallets.models.wallet_state import WalletState


wallet_model = EOAWallet(
    id="550e8400-e29b-41d4-a716-446655440009",
    address="0x9876543210fedcba9876543210fedcba98765432",
    blockchain=Blockchain.ETH_MINUS_SEPOLIA,
    custody_type=CustodyType.DEVELOPER,
    state=WalletState.LIVE,
    wallet_set_id="550e8400-e29b-41d4-a716-446655440002",
    account_type="EOA",
    create_date="2023-01-01T10:00:00Z",
    update_date="2023-01-01T11:00:00Z"
)


wallet_dict = wallet_model.to_dict()
wallet_json = wallet_model.to_json()
wallet_from_dict = EOAWallet.from_dict(wallet_dict)
wallet_from_json = EOAWallet.from_json(wallet_json)
```