bitcoin-core-rpc

A standalone JSON-RPC client against Bitcoin Core. As used by the btclib library.

One source file with nothing but the standard library behind it, fully annotated and shipping py.typed. BitcoinCoreRpcClient invokes any one rpc method a node has, with positional or named parameters: one HTTP POST per call, basic authentication, the result or an exception.

Install it, or copy the file — Vendoring below is how, and it is a supported way to use this rather than a fallback.

pip install bitcoin-core-rpc

Talking to a node

from_chain is the local node of one of Core's chains: the loopback url, the port and the cookie file all come from Core's own defaults, so a node started with none of them overridden needs no arguments at all.

from bitcoin_core_rpc import BitcoinCoreRpcClient

client = BitcoinCoreRpcClient.from_chain("main")
print(client.call("getblockcount"))
print(client.call("getblockchaininfo")["chain"])

The credential is the cookie file bitcoind rewrites at every start, read at each call rather than held: a client built when the node was up still works an hour and a restart later. The datadir it is looked for under is Core's own for the platform running — %APPDATA%\Bitcoin on Windows, ~/Library/Application Support/Bitcoin on macOS, ~/.bitcoin elsewhere — so from_chain needs no help on any of the three. A node started with -datadir= somewhere else is what nothing can derive, and there the path is an argument:

from pathlib import Path

client = BitcoinCoreRpcClient(
    "http://127.0.0.1:8332",
    cookie_path=Path("/srv/bitcoin/.cookie"),
)

rpcuser and rpcpassword are the other way. They are arguments and never part of the url: a url with user:password@ in it is refused, because that string ends up in configuration files, tracebacks and logs.

client = BitcoinCoreRpcClient(
    "http://127.0.0.1:8332", user="rpcuser", password="rpcpassword"
)

A cookie or a datadir only authenticates the node that wrote it, not the chain it is running: -chain=test and a main cookie both exist. main is from_chain's own default, so a caller who names it and gets test back either passed the wrong name or reused a cookie carried over from elsewhere — verify_chain asks getblockchaininfo once and raises BtcRpcValueError if the two disagree, rather than trusting the port and the datadir name to have agreed with the node underneath them.

client = BitcoinCoreRpcClient.from_chain("main", verify_chain=True)

Signet is the case a name cannot settle: Core answers signet for the default signet and for every custom one alike, so the challenge is what tells two of them apart. Pass the one you mean, hex or bytes, as -signetchallenge takes it; the comparison is of the p2p magic it derives, which is what makes the same challenge in upper case the same challenge.

client = BitcoinCoreRpcClient.from_chain(
    "signet", verify_chain=True, signet_challenge="512102...ae"
)

assert_chain is that check on its own, for a client built at a url of your own — a node on another host, or behind a proxy — where there is no from_chain to ask for it.

client = BitcoinCoreRpcClient("https://node.example/", user="u", password="p")
client.assert_chain("signet", signet_challenge="512102...ae")

Calling

params is one value, shaped as JSON-RPC shapes it: a sequence for the positional form, a mapping for the named one. Core takes both, and which one a method wants is the method's business.

block_id = client.call("getblockhash", [700_000])
block = client.call("getblock", {"blockhash": block_id, "verbosity": 2})

Amounts do not travel as binary floating point in either direction: a number in the reply decodes as a Decimal, and a Decimal parameter is refused rather than rounded through float.

balance = client.for_wallet("hot").call("getbalance")   # Decimal, exact

for_wallet is the /wallet/<name> endpoint of a node with several wallets loaded, with the name percent-encoded — a wallet is a directory and may be called anything a filesystem accepts. Every wallet's client is derived from the client built for the node: calling it on a client that is already a wallet endpoint is refused rather than composing /wallet/hot/wallet/cold, which is no path Core serves.

Attribute-style calls

RpcChannel wraps a client for a caller who wants rpc.getblockcount() over client.call("getblockcount") and has weighed the trade in COMPARISON.md: an unknown method is a request to the node rather than an AttributeError here.

from bitcoin_core_rpc import BitcoinCoreRpcClient, RpcChannel

rpc = RpcChannel(BitcoinCoreRpcClient.from_chain("main"))
print(rpc.getblockcount())
print(rpc.getblock(blockhash=block_id, verbosity=2))

Positional arguments become the sequence form of params, named ones the mapping form — never both at once, json-rpc having one shape per call. request_timeout and max_body_size, call's own keyword-only controls, reach call rather than travelling to the node as a named parameter; every other name starting with _, dunders included, is an AttributeError instead of a request, which is what keeps copy.deepcopy and an interactive shell's attribute probing from becoming one.

When it goes wrong

Three exceptions, because there are three different things to do about them. All three are FetchError, so one except FetchError covers the lot.

from bitcoin_core_rpc import FetchError, HttpError, RpcError

try:
    raw = client.call("getrawtransaction", [tx_id])
except RpcError as e:
    if e.code == -5:        # no such transaction; a node without -txindex
        ...                 # answers this for anything outside its wallet
except HttpError as e:
    if e.status == 503:     # the rpc work queue is full: try again later
        ...                 # a 401 never works again, so tell the two apart
except FetchError:
    ...                     # refused connection, expired timeout, no answer

There is no retry, and it is deliberate: call carries any method, so this client cannot know whether re-sending one is safe, and a timeout is not a deadline — a node that stopped answering may still be executing the call. HttpError.status is what makes a caller's own policy three lines rather than a match on the text of a message.

What it does not do

• batches. One call is one HTTP request. A batch needs an api for correlating the answers and for partly failing, which is a question of its own; a loop over call is the replacement, an equivalent beside the node and not over a link where the round trip costs something.
• notifications, a request sent with no id, which a node does not answer.
• retries, per above.
• redirects. A 30x arrives as an HttpError rather than as a second request: the first one already carries the Authorization for the host it names, and following the redirect would send that credential wherever the Location points.
• proxies from the environment. HTTP_PROXY is set for a browser or a package manager and inherited by everything in the shell, which is the wrong source for the decision of where a wallet command is sent. A caller who does want one passes a transport.

Migrating from AuthServiceProxy

It is not python-bitcoinrpc's AuthServiceProxy and not a port of it. That class, and the copy of it Core's test framework maintains, carry the LGPL-2.1 of their python-jsonrpc ancestry, where this is MIT: this is an implementation of the protocol and shares no line with either. What a caller rewrites is below, an AuthServiceProxy line at a time with the same command under it.

Connecting. The credential is an argument, and a url carrying user:password@ is refused rather than accepted and stripped: that url is the string that ends up in a configuration file, a traceback and a log.

# AuthServiceProxy
rpc = AuthServiceProxy(f"http://{user}:{password}@127.0.0.1:8332")

# this client
client = BitcoinCoreRpcClient(
    "http://127.0.0.1:8332", user=user, password=password
)

A node left on its defaults needs neither argument: from_chain has the port and the cookie file, per Talking to a node.

Invoking a method. The method is an argument and not an attribute: any name a node has works without this class knowing it, and none of them can collide with a name of the client's own. params is then one argument as well, a sequence for the positional form and a mapping for the named one.

# AuthServiceProxy
block = rpc.getblock(block_id, 2)

# this client
block = client.call("getblock", [block_id, 2])
block = client.call("getblock", {"blockhash": block_id, "verbosity": 2})

A wallet command. /wallet/<name> is derived from the client rather than written into a second url, and the name is percent-encoded.

# AuthServiceProxy
hot = AuthServiceProxy(f"http://{user}:{password}@127.0.0.1:8332/wallet/hot")
balance = hot.getbalance()

# this client
balance = client.for_wallet("hot").call("getbalance")

A batch. There is none, per What it does not do, and a loop is what replaces it: the calls go one HTTP request each rather than several in one, and each answer is a value or an exception where a batch answered with a list to inspect.

# AuthServiceProxy
hashes = rpc.batch_([["getblockhash", height] for height in heights])

# this client
hashes = [client.call("getblockhash", [height]) for height in heights]

An error. JSONRPCException becomes three exceptions, and When it goes wrong above has the table: RpcError for an error the node computed, HttpError for an exchange that failed and FetchError for no answer to read. All three are FetchError, so except FetchError is the translation that catches what the one exception caught.

COMPARISON.md has the case for the switch beyond this rewrite guide, and why the features this client does not have — and the one, dynamic dispatch, offered differently instead — are decisions rather than omissions.

Testing code that calls a node

transport is the seam, and it is public for this: a callable taking the request and a timeout, answering with the HTTP status and the body. The suite of this project opens no socket, and neither has yours to.

import json

def transport(request, timeout):
    request_id = json.loads(request.data)["id"]
    body = {"jsonrpc": "2.0", "id": request_id, "result": 481824}
    return 200, json.dumps(body).encode()

client = BitcoinCoreRpcClient(
    "http://127.0.0.1:8332", user="u", password="p", transport=transport
)
assert client.call("getblockcount") == 481824

What a transport of your own owes, none of which this module can check for it: its own bound on what it holds in memory while reading, its own bound on how long it holds the call — most client libraries spend timeout per socket operation, which a peer dripping a body resets forever — no redirect followed, and its own thread safety.

Type checking

The source is annotated throughout, mypy --strict runs over it here, and the distribution ships py.typed — so your own checker reads those annotations with no configuration of any kind:

$ mypy --strict your_code.py
your_code.py:4: error: Argument 1 to "call" of "BitcoinCoreRpcClient" has
incompatible type "int"; expected "str"

That marker is why the source is bitcoin_core_rpc/__init__.py and not a top-level module: PEP 561 puts it inside a package directory and nowhere else. pyproject.toml records what the alternatives were measured to do.

Vendoring

Copy bitcoin_core_rpc/__init__.py whole from a release tag, rename it to bitcoin_core_rpc.py, keep the license notice at the top of it — MIT, embedded rather than referenced, because a copy has no LICENSE beside it — and record the tag next to the copy. An update is a replacement of the whole file, and this shows every behavioral change first:

git diff OLD..NEW -- bitcoin_core_rpc/__init__.py

A vendored copy receives no security or compatibility fix automatically, so its recorded tag is what says whether it needs replacing. An installed one is a version an ordinary dependency bump moves, which is why installing is the default advice.

Security

Basic authentication is cleartext over plain HTTP, that being what Core's rpc speaks. On loopback that cleartext is between one process and the node beside it; for a node anywhere else it is on the wire, and rpc credentials authorise every wallet command that node has. SECURITY.md carries the rest, and how to report a vulnerability.

Contributing

CONTRIBUTING.md has the commands each CI job runs, verbatim. uv sync creates the environment; uv is the only tool that has to be installed.

Links

• Documentation: https://bitcoin-core-rpc.readthedocs.io/
• Source: https://github.com/btclib-org/bitcoin-core-rpc
• Releases: https://github.com/btclib-org/bitcoin-core-rpc/releases
• CHANGELOG.md, and HISTORY.md for what a release asks a user to act on