Migration Guide

Migrating from v6 to v7

web3.py follows Semantic Versioning, which means that version 7 introduced backwards-incompatible changes. If you’re upgrading from web3.py v6 or earlier, you can expect to need to make some changes. Refer to this guide for a summary of breaking changes when updating from v6 to v7. If you are more than one major version behind, you should also review the migration guides for the versions in between.

Provider Updates


WebsocketProviderV2, introduced in web3.py v6, has taken priority over the legacy WebsocketProvider. The LegacyWebSocketProvider has been deprecated in v7 and is slated for removal in the next major version of the library. In summary:

  • WebsocketProvider -> LegacyWebSocketProvider (and deprecated)

  • WebsocketProviderV2 -> WebSocketProvider

If migrating from WebSocketProviderV2 to WebSocketProvider, you can expect the following changes:

  • Instantiation no longer requires the persistant_websocket method:

    # WebsocketsProviderV2:
    # WebSocketProvider:
  • Handling incoming subscription messages now occurs under a more flexible namespace: socket. The AsyncIPCProvider uses the same API to listen for messages via an IPC socket.

    # WebsocketsProviderV2:
    async for message in w3.ws.process_subscriptions():
    # WebSocketProvider:
    async for message in w3.socket.process_subscriptions():

AsyncIPCProvider (non-breaking feature)

An asynchronous IPC provider, AsyncIPCProvider, is newly available in v7. This provider makes use of some of the same internals that the new WebSocketProvider introduced, allowing it to also support eth_subscription.


EthereumTesterProvider now returns input instead of data for eth_getTransaction* calls, as expected.

Middlewares -> Middleware

All references to middlewares have been replaced with the more grammatically correct middleware. Notably, this includes when a provider needs to be instantiated with custom middleware.

Class-Based Middleware Model

The middleware model has been changed to a class-based model. Previously, middleware were defined as functions that tightly wrapped the provider’s make_request function, where transformations could be conditionally applied before and after the request was made.

Now, middleware logic can be separated into request_processor and response_processor functions that enable pre-request and post-response logic, respectively. This change offers a simpler, clearer interface for defining middleware, gives more flexibility for asynchronous operations and also paves the way for supporting batch requests - included in the roadmap for web3.py.

The new middleware model is documented in the Middleware section.

Middleware Renaming and Removals

The following middleware have been renamed for generalization or clarity:

  • name_to_address_middleware -> ENSNameToAddressMiddleware

  • geth_poa_middleware -> ExtraDataToPOAMiddleware

The following middleware have been removed:

ABI Middleware

abi_middleware is no longer necessary and has been removed. All of the functionality of the abi_middleware was already handled by web3.py’s ABI formatters. For additional context: a bug in the ENS name-to-address middleware would override the formatters. Fixing this bug has removed the need for the abi_middleware.

Caching Middleware

The following middleware have been removed:

  • simple_cache_middleware

  • latest_block_based_cache_middleware

  • time_based_cache_middleware

All caching middleware has been removed in favor of a decorator/wrapper around the make_request methods of providers with configuration options on the provider class. The configuration options are outlined in the documentation in the Request Caching section.

If desired, the previous caching middleware can be re-created using the new class-based middleware model overriding the wrap_make_request (or async_wrap_make_request) method in the middleware class.

Result Generating Middleware

The following middleware have been removed:

  • fixture_middleware

  • result_generator_middleware

The fixture_middleware and result_generator_middleware which were used for testing/mocking purposes have been removed. These have been replaced internally by the RequestMocker class, utilized for testing via a request_mocker pytest fixture.

HTTP Retry Request Middleware

The http_retry_request_middleware has been removed in favor of a configuration option on the HTTPProvider and AsyncHTTPProvider classes. The configuration options are outlined in the documentation in the Retry Requests for HTTP Providers section.

Normalize Request Parameters Middleware

The normalize_request_parameters middleware was not used anywhere internally and has been removed.

Remaining camelCase -> snake_case Updates

The following arguments have been renamed across the library from camelCase to snake_case in all methods where they are passed in as a kwarg.

  • fromBlock -> from_block

  • toBlock -> to_block

  • blockHash -> block_hash

Note that if a dictionary is used instead, say to a call such as eth_getLogs, the keys in the dictionary should be camelCase. This is because the dictionary is passed directly to the JSON-RPC request, where the keys are expected to be in camelCase.

Changes to Exception Handling

All Python standard library exceptions that were raised from within web3.py have been replaced with custom Web3Exception classes. This change allows for better control over exception handling, being able to distinguish between exceptions raised by web3.py and those raised from elsewhere in a codebase. The following exceptions have been replaced:

  • AssertionError -> Web3AssertionError

  • ValueError -> Web3ValueError

  • TypeError -> Web3TypeError

  • AttributeError -> Web3AttributeError

A new MethodNotSupported exception is now raised when a method is not supported by web3.py. This allows a user to distinguish between when a method is not available on the current provider, MethodUnavailable, and when a method is not supported by web3.py under certain conditions, MethodNotSupported.

JSON-RPC Error Handling

Rather than a ValueError being replaced with a Web3ValueError when a JSON-RPC response comes back with an error object, a new Web3RPCError exception is now raised to provide more distinction for JSON-RPC error responses. Some previously existing exceptions now extend from this class since they too are related to JSON-RPC errors:

  • MethodUnavailable

  • BlockNotFound

  • TransactionNotFound

  • TransactionIndexingInProgress

End of Support and Feature Removals

Python 3.7 Support Dropped

Python 3.7 support has been dropped in favor of Python 3.8+. Python 3.7 is no longer supported by the Python core team, and we want to focus our efforts on supporting the latest versions of Python.

EthPM Module Removed

The EthPM module has been removed from the library. It was not widely used and has not been functional since around October 2022. It was deprecated in v6 and has been completely removed in v7.

Geth Miner Namespace Removed

The geth.miner namespace, deprecated in v6, has been removed in v7. The miner namespace was used for managing the concept of a miner in geth. This is no longer a feature in geth and is planned for complete removal in the future, with Ethereum having transitioned to proof-of-stake.

Geth Personal Namespace Removed

The geth.personal namespace, deprecated in v6, has been removed in v7. The personal namespace was used for managing accounts and keys and was deprecated in geth in v1.11.0. Geth has moved to using clef for account and key management.

Miscellaneous Changes

  • LRU has been removed from the library and dependency on lru-dict library was dropped.

  • CallOverride type was changed to StateOverride since more methods than eth_call utilize the state override params.

  • User-Agent header was changed to a more readable format.

  • BaseContractFunctions iterator now returns instances of ContractFunction rather than the function names.

  • Beacon API filename change: beacon/main.py -> beacon/beacon.py.

  • The asynchronous version of w3.eth.wait_for_transaction_receipt() changes its signature to use Optional[float] instead of float since it may be None.

  • get_default_ipc_path() and get_dev_ipc_path() now return the path value without checking if the geth.ipc file exists.

  • Web3.is_address() returns True for non-checksummed addresses.

  • Contract.encodeABI() has been renamed to Contract.encode_abi().

  • JSON-RPC responses are now more strictly validated against the JSON-RPC 2.0 specification while providing more informative error messages for invalid responses.

Migrating from v5 to v6

web3.py follows Semantic Versioning, which means that version 6 introduced backwards-incompatible changes. If your project depends on web3.py v6, then you’ll probably need to make some changes.

Breaking Changes:

Strict Bytes Checking by Default

web3.py v6 moved to requiring strict bytes checking by default. This means that if an ABI specifies a bytes4 argument, web3.py will invalidate any entry that is not encodable as a bytes type with length of 4. This means only 0x-prefixed hex strings with a length of 4 and bytes types with a length of 4 will be considered valid. This removes doubt that comes from inferring values and assuming they should be padded.

This behavior was previously available in via the w3.enable_strict_bytes_checking() method. This is now, however, a toggleable flag on the Web3 instance via the w3.strict_bytes_type_checking property. As outlined above, this property is set to True by default but can be toggled on and off via the property’s setter (e.g. w3.strict_bytes_type_checking = False).

Snake Case

web3.py v6 moved to the more Pythonic convention of snake_casing wherever possible. There are some exceptions to this pattern:

  • Contract methods and events use whatever is listed in the ABI. If the smart contract convention is to use camelCase for method and event names, web3.py won’t do any magic to convert it to snake_casing.

  • Arguments to JSON-RPC methods. For example: transaction and filter parameters still use camelCasing. The reason for this is primarily due to error messaging. It would be confusing to pass in a snake_cased parameter and get an error message with a camelCased parameter.

  • Data that is returned from JSON-RPC methods. For example: The keys in a transaction receipt will still be returned as camelCase.

Python 3.10 and 3.11 Support

Support for Python 3.10 and 3.11 is here. In order to support Python 3.10, we had to update the websockets dependency to v10+.


Exceptions inherit from a base class

In v5, some web3.py exceptions inherited from AttributeError, namely:

  • NoABIFunctionsFound

  • NoABIFound

  • NoABIEventsFound

Others inherited from ValueError, namely:

  • InvalidAddress

  • NameNotFound

  • LogTopicError

  • InvalidEventABI

Now web3.py exceptions inherit from the same base Web3Exception.

As such, any code that was expecting a ValueError or an AttributeError from web3.py must update to expecting one of the exceptions listed above, or Web3Exception.

Similarly, exceptions raised in the EthPM and ENS modules inherit from the base EthPMException and ENSException, respectively.


The Python dev tooling ecosystem is moving towards standardizing ValidationError, so users know that they’re catching the correct ValidationError. The base ValidationError is imported from eth_utils. However, we also wanted to empower users to catch all errors emitted by a particular module. So we now have a Web3ValidationError, EthPMValidationError, and an ENSValidationError that all inherit from the generic eth_utils.exceptions.ValidationError.

Web3 class split into Web3 and AsyncWeb3

The Web3 class previously contained both sync and async methods. We’ve separated Web3 and AsyncWeb3 functionality to tighten up typing. For example:

from web3 import Web3, AsyncWeb3

w3 = Web3(Web3.HTTPProvider(<provider.url>))
async_w3 = AsyncWeb3(AsyncWeb3.AsyncHTTPProvider(<provider.url>))

dict to AttributeDict conversion moved to middleware

Eth module data returned as key-value pairs was previously automatically converted to an AttributeDict by result formatters, which could cause problems with typing. This conversion has been moved to a default attrdict_middleware where it can be easily removed if necessary. See the Eth module docs for more detail.

Other Misc Changes

  • InfuraKeyNotFound exception has been changed to InfuraProjectIdNotFound

  • SolidityError has been removed in favor of ContractLogicError

  • When a method is unavailable from a node provider (i.e. a response error code of -32601 is returned), a MethodUnavailable error is now raised instead of ValueError

  • Logs’ data field was previously formatted with to_ascii_if_bytes, now formatted to HexBytes

  • Receipts’ type field was previously not formatted, now formatted with to_integer_if_hex


  • Removed unused IBAN module

  • Removed WEB3_INFURA_API_KEY environment variable in favor of WEB3_INFURA_PROJECT_ID

  • Removed Kovan auto provider

  • Removed deprecated sha3 and soliditySha3 methods in favor of keccak and solidityKeccak

  • Remove Parity Module and References

Other notable changes

  • The ipfshttpclient library is now opt-in via a web3 install extra. This only affects the ethpm ipfs backends, which rely on the library.

Migrating from v4 to v5

Web3.py follows Semantic Versioning, which means that version 5 introduced backwards-incompatible changes. If your project depends on Web3.py v4, then you’ll probably need to make some changes.

Here are the most common required updates:

Python 3.5 no longer supported

You will need to upgrade to either Python 3.6 or 3.7

eth-abi v1 no longer supported

You will need to upgrade the eth-abi dependency to v2

Changes to base API

JSON-RPC Updates

In v4, JSON-RPC calls that looked up transactions or blocks and didn’t find them, returned None. Now if a transaction or block is not found, a BlockNotFound or a TransactionNotFound error will be thrown as appropriate. This applies to the following web3 methods:

  • getTransaction() will throw a TransactionNotFound error

  • getTransactionReceipt() will throw a TransactionNotFound error

  • getTransactionByBlock() will throw a TransactionNotFound error

  • getTransactionCount() will throw a BlockNotFound error

  • getBlock() will throw a BlockNotFound error

  • getUncleCount() will throw a BlockNotFound error

  • getUncleByBlock() will throw a BlockNotFound error

Removed Methods

  • contract.buildTransaction was removed for contract.functions.buildTransaction.<method name>

  • contract.deploy was removed for contract.constructor.transact

  • contract.estimateGas was removed for contract.functions.<method name>.estimateGas

  • contract.call was removed for contract.<functions/events>.<method name>.call

  • contract.transact was removed for contract.<functions/events>.<method name>.transact

  • contract.eventFilter was removed for contract.events.<event name>.createFilter

  • middleware_stack was renamed to middleware_onion()

  • web3.miner.hashrate was a duplicate of hashrate() and was removed.

  • web3.version.network was a duplicate of version() and was removed.

  • web3.providers.tester.EthereumTesterProvider and web3.providers.tester.TestRPCProvider have been removed for EthereumTesterProvider()

  • web3.eth.enableUnauditedFeatures was removed

  • web3.txpool was moved to txpool()

  • web3.version.node was removed for web3.clientVersion

  • web3.version.ethereum was removed for protocolVersion()

  • Relocated personal RPC endpoints to reflect Parity and Geth implementations:

    • web3.personal.listAccounts was removed for listAccounts() or listAccounts()

    • web3.personal.importRawKey was removed for importRawKey() or importRawKey()

    • web3.personal.newAccount was removed for newAccount() or newAccount()

    • web3.personal.lockAccount was removed for lockAccount()

    • web3.personal.unlockAccount was removed for unlockAccount() or unlockAccount()

    • web3.personal.sendTransaction was removed for sendTransaction() or sendTransaction()

  • Relocated web3.admin module to web3.geth namespace

  • Relocated web3.miner module to web3.geth namespace

Deprecated Methods

Expect the following methods to be removed in v6:

  • web3.sha3 was deprecated for keccak()

  • web3.soliditySha3 was deprecated for solidityKeccak()

  • chainId() was deprecated for chainId(). Follow issue #1293 for details

  • web3.eth.getCompilers() was deprecated and will not be replaced

  • getTransactionFromBlock() was deprecated for getTransactionByBlock()

Deprecated ConciseContract and ImplicitContract

The ConciseContract and ImplicitContract have been deprecated and will be removed in v6.

ImplicitContract instances will need to use the verbose syntax. For example:

contract.functions.<function name>.transact({})

ConciseContract has been replaced with the ContractCaller API. Instead of using the ConciseContract factory, you can now use:


or the classic contract syntax:

contract.functions.<function name>.call().

Some more concrete examples can be found in the ContractCaller docs

Manager Provider

In v5, only a single provider will be allowed. While allowing multiple providers is a feature we’d like to support in the future, the way that multiple providers was handled in v4 wasn’t ideal. The only thing they could do was fall back. There was no mechanism for any round robin, nor was there any control around which provider was chosen. Eventually, the idea is to expand the Manager API to support injecting custom logic into the provider selection process.

For now, manager.providers has changed to manager.provider. Similarly, instances of web3.providers have been changed to web3.provider.

Testnet Changes

Web3.py will no longer automatically look up a testnet connection in IPCProvider.


Web3.py has stopped inferring the .eth TLD on domain names. If a domain name is used instead of an address, you’ll need to specify the TLD. An InvalidTLD error will be thrown if the TLD is missing.

Required Infura API Key

In order to interact with Infura after March 27, 2019, you’ll need to set an environment variable called WEB3_INFURA_PROJECT_ID. You can get a project id by visiting https://infura.io/register.

Migrating from v3 to v4

Web3.py follows Semantic Versioning, which means that version 4 introduced backwards-incompatible changes. If your project depends on Web3.py v3, then you’ll probably need to make some changes.

Here are the most common required updates:

Python 2 to Python 3

Only Python 3 is supported in v4. If you are running in Python 2, it’s time to upgrade. We recommend using 2to3 which can make most of your code compatible with Python 3, automatically.

The most important update, relevant to Web3.py, is the new bytes type. It is used regularly, throughout the library, whenever dealing with data that is not guaranteed to be text.

Many different methods in Web3.py accept text or binary data, like contract methods, transaction details, and cryptographic functions. The following example uses sha3(), but the same pattern applies elsewhere.

In v3 & Python 2, you might have calculated the hash of binary data this way:

>>> Web3.sha3('I\xe2\x99\xa5SF')

Or, you might have calculated the hash of text data this way:

>>> Web3.sha3(text=u'I♥SF')

After switching to Python 3, these would instead be executed as:

>>> Web3.sha3(b'I\xe2\x99\xa5SF')

>>> Web3.sha3(text='I♥SF')

Note that the return value is different too: you can treat hexbytes.main.HexBytes like any other bytes value, but the representation on the console shows you the hex encoding of those bytes, for easier visual comparison.

It takes a little getting used to, but the new py3 types are much better. We promise.


Filters usually don’t work quite the way that people want them to.

The first step toward fixing them was to simplify them by removing the polling logic. Now, you must request an update on your filters explicitly. That means that any exceptions during the request will bubble up into your code.

In v3, those exceptions (like “filter is not found”) were swallowed silently in the automated polling logic. Here was the invocation for printing out new block hashes as they appear:

>>> def new_block_callback(block_hash):
...     print(f"New Block: {block_hash}")
>>> new_block_filter = web3.eth.filter('latest')
>>> new_block_filter.watch(new_block_callback)

In v4, that same logic:

>>> new_block_filter = web3.eth.filter('latest')
>>> for block_hash in new_block_filter.get_new_entries():
...     print(f"New Block: {block_hash}")

The caller is responsible for polling the results from get_new_entries(). See Asynchronous Filter Polling for examples of filter-event handling with web3 v4.

TestRPCProvider and EthereumTesterProvider

These providers are fairly uncommon. If you don’t recognize the names, you can probably skip the section.

However, if you were using web3.py for testing contracts, you might have been using TestRPCProvider or EthereumTesterProvider.

In v4 there is a new EthereumTesterProvider, and the old v3 implementation has been removed. Web3.py v4 uses eth_tester.main.EthereumTester under the hood, instead of eth-testrpc. While eth-tester is still in beta, many parts are already in better shape than testrpc, so we decided to replace it in v4.

If you were using TestRPC, or were explicitly importing EthereumTesterProvider, like: from web3.providers.tester import EthereumTesterProvider, then you will need to update.

With v4 you should import with from web3 import EthereumTesterProvider. As before, you’ll need to install Web3.py with the tester extra to get these features, like:

$ pip install web3[tester]

Changes to base API convenience methods


In v4 Web3.toDecimal() is renamed: toInt() for improved clarity. It does not return a decimal.Decimal, it returns an int.

Removed Methods

  • Web3.toUtf8 was removed for toText().

  • Web3.fromUtf8 was removed for toHex().

  • Web3.toAscii was removed for toBytes().

  • Web3.fromAscii was removed for toHex().

  • Web3.fromDecimal was removed for toHex().

Provider Access

In v4, w3.currentProvider was removed, in favor of w3.providers.

Disambiguating String Inputs

There are a number of places where an arbitrary string input might be either a byte-string that has been hex-encoded, or unicode characters in text. These are named hexstr and text in Web3.py. You specify which kind of str you have by using the appropriate keyword argument. See examples in Encoding and Decoding Helpers.

In v3, some methods accepted a str as the first positional argument. In v4, you must pass strings as one of hexstr or text keyword arguments.

Notable methods that no longer accept ambiguous strings:

  • sha3()

  • toBytes()


  • When a contract returns the ABI type string, Web3.py v4 now returns a str value by decoding the underlying bytes using UTF-8.

  • When a contract returns the ABI type bytes (of any length), Web3.py v4 now returns a bytes value

Personal API

w3.personal.signAndSendTransaction is no longer available. Use w3.personal.sendTransaction() instead.