Hermes Python client
Async Python client for the Hermes gRPC search server.
Installation
pip install hermes-client-python
Python 3.10 or newer is required.
Quick start
import asyncio
from hermes_client_python import HermesClient
async def main():
async with HermesClient("localhost:50051") as client:
await client.create_index(
"articles",
"""
index articles {
field title: text<simple> [indexed, stored]
field body: text<simple> [indexed, stored]
}
""",
)
indexed, error_count, errors = await client.index_documents(
"articles",
[
{"title": "Hello World", "body": "First article"},
{"title": "Hermes Search", "body": "Fast retrieval"},
],
)
if error_count:
raise RuntimeError(errors)
print(f"Indexed {indexed} documents")
await client.commit("articles")
results = await client.search(
"articles",
query={"match": {"field": "title", "text": "hello"}},
fields_to_load=["title", "body"],
)
for hit in results.hits:
print(hit.address, hit.score, hit.fields)
if results.hits:
document = await client.get_document("articles", results.hits[0].address)
print(document.fields if document else "document not found")
await client.delete_index("articles")
asyncio.run(main())
The context manager calls connect() and close() automatically. For manual
lifecycle management:
client = HermesClient("localhost:50051")
await client.connect()
try:
...
finally:
await client.close()
Index management
await client.create_index("articles", schema_sdl)
names = await client.list_indexes()
info = await client.get_index_info("articles")
print(info.num_docs, info.num_segments, info.vector_stats)
await client.force_merge("articles")
await client.reorder("articles")
await client.retrain_vector_index("articles")
await client.delete_index("articles")
commit() is required before newly indexed documents become searchable.
Batch and streaming indexing
indexed, error_count, errors = await client.index_documents(
"articles",
[
{"title": "One", "tags": ["search", "rust"]},
{"title": "Two", "tags": ["python"]},
],
)
async def documents():
for number in range(10_000):
yield {"title": f"Document {number}"}
streamed, stream_errors = await client.index_documents_stream("articles", documents())
Repeated list values become repeated field entries. Flat numeric lists are
dense vectors; lists of (dimension, weight) pairs are sparse vectors.
Searching
Every search takes one query object whose single key matches a Hermes query
variant:
# Exact term
await client.search(
"articles",
query={"term": {"field": "title", "term": "hermes"}},
)
# Tokenized full-text match
await client.search(
"articles",
query={"match": {"field": "body", "text": "fast retrieval"}},
)
# Recursive boolean query
await client.search(
"articles",
query={
"boolean": {
"must": [{"match": {"field": "body", "text": "retrieval"}}],
"must_not": [{"term": {"field": "title", "term": "draft"}}],
}
},
)
# Dense vector query and optional reranking
await client.search(
"articles",
query={
"dense_vector": {
"field": "embedding",
"vector": [0.1, 0.2, 0.3],
"nprobe": 16,
}
},
reranker={"field": "embedding", "vector": [0.1, 0.2, 0.3]},
candidate_limit=20,
limit=10,
fields_to_load=["title"],
)
# Hybrid union fusion
await client.search(
"articles",
query={
"fusion": {
"method": "rrf",
"rrf_k": 60,
"queries": [
{
"query": {
"sparse_vector": {
"field": "sparse_embedding",
"indices": [1, 5],
"values": [0.8, 0.2],
}
},
"weight": 1.0,
},
{
"query": {
"dense_vector": {
"field": "embedding",
"vector": [0.1, 0.2, 0.3],
}
},
"weight": 1.0,
},
],
}
},
)
Other supported variants are binary_dense_vector, boost, range,
prefix, and all. Search results expose the full DocAddress needed by
get_document():
hit = results.hits[0]
document = await client.get_document("articles", hit.address)
Deadlines and errors
Every RPC accepts an optional timeout in seconds. A per-call value overrides
the client default:
client = HermesClient("localhost:50051", default_timeout=5.0)
results = await client.search(
"articles",
query={"all": {}},
timeout=0.5,
)
await client.force_merge("articles", timeout=3600)
gRPC failures raise grpc.RpcError (normally
grpc.aio.AioRpcError). get_document() is the exception: it returns None
for NOT_FOUND.
import grpc
try:
await client.search("missing", query={"all": {}})
except grpc.RpcError as error:
if error.code() == grpc.StatusCode.NOT_FOUND:
print("index not found")
else:
raise
Development
From hermes-client-python:
uv sync --group dev --group test
uv run ruff check .
uv run ruff format --check .
uv run pytest tests/test_client_unit.py
The remaining tests are integration tests and expect a debug
target/debug/hermes-server binary. Regenerate checked-in protobuf stubs after
changing hermes-proto/hermes.proto:
uv run --group dev python generate_proto.py
License
MIT
1 maintainer
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