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SUBMIT A PRSUBMIT AN ISSUElast edit: Apr 10, 2025

Managing Subtensor Connections

Every time the Bittensor Python SDK's Subtensor or AsyncSubtensor class is instantiated, it creates a new websocket connection to Subtensor, Bittensor's Blockchain. Your code should ensure that these websocket connections are handled efficiently and closed when no longer in use by your code.

If not explicitly closed, connections should be terminated by Python's garbage collector, but threading can make this unreliable. (see this comment.)

Therefore, the best solution is to always use one of the following techniques to close your instance's connection:

  1. Use the close() method to manually terminate the instance and connection.
  2. (Preferred) Use the with keyword to instantiate the Subtensor object within a Python context manager. This ensures the websocket connection within the Subtensor instance is terminated gracefully when the context ends.
tip

You don't need to both a with-statement context manager and .close(), just one or the other.

What not to do​

import bittensor as bt
sub = bt.subtensor("finney")
# calls to subtensor

# no close
# potential resource leak:
# the connection is open until/unless garbage collected

With close()​

Sync​

import bittensor as bt
sub = bt.subtensor("finney")
# subtensor calls
sub.close()
# instance and connection are terminated.

Async​

import bittensor as bt
sub = bt.AsyncSubtensor()
await sub.initialize()
# calls to subtensor
await sub.close()
# instance and connection are terminated.

With with​

Sync​

import bittensor as bt
with bt.subtensor("finney") as sub:
    # all calls to subtensor instance inside this block


# instance and connection are terminated at the end of the context scope

Async​

import bittensor as bt
async with bt.AsyncSubtensor() as sub:
    # calls to subtensor

# instance and connection are terminated at the end of the context scope

or

import bittensor as bt
sub = bt.AsyncSubtensor()
async with sub:
    # calls to subtensor

# instance and connection are terminated at the end of the context scope