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pycoin -- Python Cryptocoin Utilities

The pycoin library implements many utilities useful when dealing with bitcoin and some bitcoin-like alt-coins. It has been tested with Python 2.7, 3.6 and 3.7.

See also pycoinnet for a library that speaks the bitcoin protocol.

Documentation at readthedocs

Discussion at zulipchat

Networks

As of 0.9, pycoin supports many coins to various degrees via the "network" class. Since specifications vary based on the network (for example, bitcoin mainnet addresses start with a "1", but testnet addresses start with an "m" or "n"), all API descends from a network object. Everything related to a particular network is scoped under this class.

Bitcoin has the highest level of support, including keys, transactions, validation of signed transactions, and signing unsigned transactions, including partial signing of multisig transactions. These are in level of increasing complexity, so features for other coins will likely be supported in that order.

There are two main ways to get a network:

from pycoin.symbols.btc import network

from pycoin.networks.registry import network_for_netcode
network = network_for_netcode("BTC")

Keys

You can create a private key and get the corresponding address.

from pycoin.symbols.btc import network

key = network.keys.private(secret_exponent=1)  # this is a terrible key because it's very guessable
print(key.wif())
print(key.sec())
print(key.address())
print(key.address(is_compressed=False))

same_key = network.parse.private(key.wif())
print(same_key.address())

BIP32

You can create a BIP32 key.

key = network.keys.bip32_seed(b"foo")  # this is a terrible key because it's very guessable
print(key.hwif(as_private=1))
print(key.hwif())
print(key.wif())
print(key.sec())
print(key.address())

You can parse a BIP32 key.

key = network.parse.bip32("xprv9s21ZrQH143K31AgNK5pyVvW23gHnkBq2wh5aEk6g1s496M"
      "8ZMjxncCKZKgb5jZoY5eSJMJ2Vbyvi2hbmQnCuHBujZ2WXGTux1X2k9Krdtq")
print(key.hwif(as_private=1))
print(key.hwif())
print(key.wif())
print(key.sec())
print(key.address())

WARNING: be extremely careful giving out public wallet keys. If someone has access to a private wallet key P, of course they have access to all descendent wallet keys of P. But if they also have access to a public wallet key K where P is a subkey of K, you can actually work your way up the tree to determine the private key that corresponds to the public wallet key K (unless private derivation was used at some point between the two keys)! Be sure you understand this warning before giving out public wallet keys!

Much of this API is exposed in the ku command-line utility. See also COMMAND-LINE-TOOLS.md.

See BIP32.txt for more information.

Transactions

The command-line utility tx is a Swiss Army knife of transaction utilities. See also COMMAND-LINE-TOOLS.md.

Services

When signing or verifying signatures on a transaction, the source transactions are generally needed. If you set two environment variables in your .profile like this:

PYCOIN_CACHE_DIR=~/.pycoin_cache
PYCOIN_BTC_PROVIDERS="blockchain.info blockexplorer.com chain.so"
export PYCOIN_CACHE_DIR PYCOIN_BTC_PROVIDERS
export PYCOIN_XTN_PROVIDERS="blockchain.info"  # For Bitcoin testnet

and then tx will automatically fetch transactions from the web sites listed and cache the results in PYCOIN_CACHE_DIR when they are needed.

(The old syntax with PYCOIN_SERVICE_PROVIDERS is deprecated.)

The module pycoin.services includes two functions spendables_for_address, get_tx_db that look at the environment variables set to determine which web sites to use to fetch the underlying information. The sites are polled in the order they are listed in the environment variable.

Blocks

The command-line utility block will dump a block in a human-readable format. For further information, look at pycoin.block, which includes the object Block which will parse and stream the binary format of a block.

ECDSA Signing and Verification

The module pycoin.ecdsa deals with ECDSA keys directly. Important structures include:

the secret_exponent (a large integer that represents a private key)
the public_pair (a pair of large integers x and y that represent a public key)

There are a handful of functions: you can do things like create a signature, verify a signature, generate the public pair from the secret exponent, and flush out the public pair from just the x value (there are two possible values for y of opposite even/odd parity, so you include a flag indicating which value for y you want).

The pycoin.ecdsa.native module looks for both OpenSSL and libsecp256k1 (with hints from PYCOIN_LIBCRYPTO_PATH and PYCOIN_LIBSECP256K1_PATH) and calls out to these libraries if they are present to accelerate ecdsa operations. Set PYCOIN_NATIVE to openssl, secp256k1 or none to tweak this.

Example:

$ PYCOIN_NATIVE=openssl
$ export PYCOIN_NATIVE

Donate

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BIP0032