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python-bitcoinlib

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This Python library provides an easy interface to the bitcoin data structures and protocol. The approach is low-level and "ground up", with a focus on providing tools to manipulate the internals of how Bitcoin works.

"The Swiss Army Knife of Bitcoin protocol." - Wladimir J. van der Laan

Currently supported tested versions include:

  • Python 3.4
  • Python 3.3
  • Python 3.2
  • Python 2.7

Requirements

sudo apt-get install libssl-dev

The RPC interface, bitcoin.rpc, is designed to work with Bitcoin Core v0.9. Older versions mostly work but there do exist some incompatibilities.

Structure

Everything consensus critical is found in the modules under bitcoin.core. This rule is followed pretty strictly, for instance chain parameters are split into consensus critical and non-consensus-critical.

  • bitcoin.core - Basic core definitions, datastructures, and (context-independent) validation
  • bitcoin.core.bignum - Bignum handling
  • bitcoin.core.key - ECC pubkeys
  • bitcoin.core.script - Scripts and opcodes
  • bitcoin.core.scripteval - Script evaluation/verification
  • bitcoin.core.serialize - Serialization

In the future the bitcoin.core may use the Satoshi sourcecode directly as a libary. Non-consensus critical modules include the following:

  • bitcoin - Chain selection
  • bitcoin.base58 - Base58 encoding
  • bitcoin.bloom - Bloom filters (incomplete)
  • bitcoin.net - Network communication (in flux)
  • bitcoin.messages - Network messages (in flux)
  • bitcoin.rpc - Bitcoin Core RPC interface support
  • bitcoin.wallet - Wallet-related code, currently Bitcoin address and private key support

Effort has been made to follow the Satoshi source relatively closely, for instance Python code and classes that duplicate the functionality of corresponding Satoshi C++ code uses the same naming conventions: CTransaction, CBlockHeader, nValue etc. Otherwise Python naming conventions are followed.

Mutable vs. Immutable objects

Like the Bitcoin Core codebase CTransaction is immutable and CMutableTransaction is mutable; unlike the Bitcoin Core codebase this distinction also applies to COutPoint, CTxIn, CTxOut, and CBlock.

Endianness Gotchas

Rather confusingly Bitcoin Core shows transaction and block hashes as little-endian hex rather than the big-endian the rest of the world uses for SHA256. python-bitcoinlib provides the convenience functions x() and lx() in bitcoin.core to convert from big-endian and little-endian hex to raw bytes to accomodate this. In addition see b2x() and b2lx() for conversion from bytes to big/little-endian hex.

Example Code

See examples/ directory. For instance this example creates a transaction spending a pay-to-script-hash transaction output:

$ PYTHONPATH=. examples/spend-pay-to-script-hash-txout.py
<hex-encoded transaction>

Also see dust-b-gone for a simple example of Bitcoin Core wallet interaction through the RPC interface: https://github.com/petertodd/dust-b-gone

Selecting the chain to use

Do the following:

import bitcoin
bitcoin.SelectParams(NAME)

Where NAME is one of 'testnet', 'mainnet', or 'regtest'. The chain currently selected is a global variable that changes behavior everywhere, just like in the Satoshi codebase.

Unit tests

Under bitcoin/tests using test data from Bitcoin Core. To run them:

python -m unittest discover python3 -m unittest discover

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