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Ethereum Name Service (ENS)

The Ethereum Name Service (ENS) is analogous to the Domain Name Service. It enables users and developers to use human-friendly names in place of error-prone hexadecimal addresses, content hashes, and more.

The ens module is included with web3.py. It provides an interface to look up domains and addresses, add resolver records, or get and set metadata.

Note

web3.py v6.6.0 introduced ENS name normalization standard ENSIP-15. This update to ENS name validation and normalization won't affect ~99% of names but may prevent invalid names from being created and from interacting with the ENS contracts via web3.py. We feel strongly that this change, though breaking, is in the best interest of our users as it ensures compatibility with the latest ENS standards.

Setup

Create an ~ens.ENS object (named ns below) in one of three ways:

  1. Automatic detection
  2. Specify an instance of a provider <providers>
  3. From an existing web3.Web3 object
# automatic detection
from ens.auto import ns

# or, with a provider
from web3 import IPCProvider
from ens import ENS

provider = IPCProvider(...)
ns = ENS(provider)

# or, with a w3 instance
# Note: This inherits the w3 middlewares from the w3 instance and adds a stalecheck middleware to the middleware onion.
# It also inherits the provider and codec from the w3 instance, as well as the ``strict_bytes_type_checking`` flag value.
from ens import ENS
w3 = Web3(...)
ns = ENS.from_web3(w3)

Asynchronous support is available via the AsyncENS module:

from ens import AsyncENS

ns = AsyncENS(provider)

Note that an ens module instance is also available on the w3 instance. The first time it's used, web3.py will create the ens instance using ENS.from_web3(w3) or AsyncENS.from_web3(w3) as appropriate.

# instantiate w3 instance
from web3 import Web3, IPCProvider
w3 = Web3(IPCProvider(...))

# use the module
w3.ens.address('ethereum.eth')

Usage

Name Info

Get the Address for an ENS Name

from ens.auto import ns
eth_address = ns.address('ens.eth')
assert eth_address == '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7'

The ENS module has no opinion as to which TLD (Top Level Domain) you can use, but will not infer a TLD if it is not provided with the name.

Multichain Address Resolution

ENSIP-9 introduced multichain address resolution, allowing users to resolve addresses from different chains, specified by the coin type index from SLIP44. The address() method on the ENS class supports multichain address resolution via the coin_type keyword argument.

from ens.auto import ns
eth_address = ns.address('ens.eth', coin_type=60)  # ETH is coin_type 60
assert eth_address == '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7'

Get the ENS Name for an Address

domain = ns.name('0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7')

# name() also accepts the bytes version of the address
assert ns.name(b'\xfe\x89\xccz\xbb,A\x83h:\xb7\x16S\xc4\xcd\xc9\xb0-D\xb7') == domain

# confirm that the name resolves back to the address that you looked up:
assert ns.address(domain) == '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7'

Note

For accuracy, and as a recommendation from the ENS documentation on reverse resolution, the ENS module now verifies that the forward resolution matches the address with every call to get the name() for an address. This is the only sure way to know whether the reverse resolution is correct. Anyone can claim any name, only forward resolution implies that the owner of the name gave their stamp of approval.

Get the Owner of a Name

eth_address = ns.owner('exchange.eth')

Set Up Your Name and Address

Link a Name to an Address

You can set up your name so that ~ens.ENS.address will show the address it points to. In order to do so, you must already be the owner of the domain (or its parent).

ns.setup_address('ens.eth', '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7')

In the common case where you want to point the name to the owning address, you can skip the address.

ns.setup_address('ens.eth')

You can claim arbitrarily deep subdomains.

ns.setup_address('supreme.executive.power.derives.from.a.mandate.from.the.masses.ens.eth')

# wait for the transaction to be mined, then:
assert (
    ns.address('supreme.executive.power.derives.from.a.mandate.from.the.masses.ens.eth')
    == '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7'
)

Warning

Gas costs scale up with the number of subdomains!

Multichain Address Support

ENSIP-9 introduced multichain address resolution, allowing users to resolve addresses from different chains, specified by the coin type index from SLIP44. The setup_address() method on the ENS class supports multichain address setup via the coin_type keyword argument.

from ens.auto import ns
ns.setup_address('ens.eth', coin_type=60)  # ETH is coin_type 60
assert ns.address('ens.eth', coin_type=60) == '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7'

Link an Address to a Name

You can set up your address so that ~ens.ENS.name will show the name that points to it.

This is like Caller ID. It enables you and others to take an account and determine what name points to it. Sometimes this is referred to as "reverse" resolution. The ENS Reverse Resolver is used for this functionality.

ns.setup_name('ens.eth', '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7')

If you don't supply the address, ~ens.ENS.setup_name will assume you want the address returned by ~ens.ENS.address.

ns.setup_name('ens.eth')

If the name doesn't already point to an address, ~ens.ENS.setup_name will call ~ens.ENS.setup_address for you.

Wait for the transaction to be mined, then:

assert ns.name('0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7') == 'ens.eth'

Text Records

Set Text Metadata for an ENS Record

As the owner of an ENS record, you can add text metadata. A list of supported fields can be found in the ENS documentation. You'll need to setup the address first, and then the text can be set:

ns.setup_address('ens.eth', '0xFe89cc7aBB2C4183683ab71653C4cdc9B02D44b7')
ns.set_text('ens.eth', 'url', 'https://example.com')

A transaction dictionary can be passed as the last argument if desired:

transaction_dict = {'from': '0x123...'}
ns.set_text('ens.eth', 'url', 'https://example.com', transaction_dict)

If the transaction dictionary is not passed, sensible defaults will be used, and if a transaction dictionary is passed but does not have a from value, the default will be the owner.

Read Text Metadata for an ENS Record

Anyone can read the data from an ENS Record:

url = ns.get_text('ens.eth', 'url')
assert url == 'https://example.com'

Working With Resolvers

Get the Resolver for an ENS Record

You can get the resolver for an ENS name via the ~ens.ENS.resolver method.

>>> resolver = ns.resolver('ens.eth')
>>> resolver.address
'0x5B2063246F2191f18F2675ceDB8b28102e957458'

Wildcard Resolution Support

The ENS module supports Wildcard Resolution for resolvers that implement the ExtendedResolver interface as described in ENSIP-10. Resolvers that implement the extended resolver interface should return True when calling the supportsInterface() function with the extended resolver interface id "0x9061b923" and should resolve subdomains to a unique address.