[examples] Added example for spending from P2WSH output.

Author: JSwambo

examples/spend-p2wsh-txout.py

@@ -0,0 +1,91 @@
+#!/usr/bin/env python3
+
+# Copyright (C) 2014 The python-bitcoinlib developers
+#
+# This file is part of python-bitcoinlib.
+#
+# It is subject to the license terms in the LICENSE file found in the top-level
+# directory of this distribution.
+#
+# No part of python-bitcoinlib, including this file, may be copied, modified,
+# propagated, or distributed except according to the terms contained in the
+# LICENSE file.
+
+"""Low-level example of how to spend a P2WSH/BIP141 txout"""
+
+import sys
+if sys.version_info.major < 3:
+    sys.stderr.write('Sorry, Python 3.x required by this example.\n')
+    sys.exit(1)
+
+import hashlib
+
+from bitcoin import SelectParams
+from bitcoin.core import b2x, lx, COIN, COutPoint, CMutableTxOut, CMutableTxIn, CMutableTransaction, CTxInWitness, CTxWitness
+from bitcoin.core.script import CScript, CScriptWitness, OP_0, OP_CHECKSIG, SignatureHash, SIGHASH_ALL, SIGVERSION_WITNESS_V0
+from bitcoin.wallet import CBitcoinSecret, CBitcoinAddress, P2WSHBitcoinAddress
+
+SelectParams('testnet')
+
+# Create the (in)famous correct brainwallet secret key.
+h = hashlib.sha256(b'correct horse battery staple').digest()
+seckey = CBitcoinSecret.from_secret_bytes(h)
+
+# Create a witnessScript and corresponding redeemScript. Similar to a scriptPubKey
+# the redeemScript must be satisfied for the funds to be spent.
+txin_witnessScript = CScript([seckey.pub, OP_CHECKSIG])
+txin_scriptHash = hashlib.sha256(txin_witnessScript).digest()
+txin_redeemScript = CScript([OP_0, txin_scriptHash])
+
+
+# Convert the P2WSH scriptPubKey to a base58 Bitcoin address and print it.
+# You'll need to send some funds to it to create a txout to spend.
+txin_p2wsh_address = P2WSHBitcoinAddress.from_scriptPubKey(txin_redeemScript)
+print('Pay to:', str(txin_p2wsh_address))
+
+# Same as the txid:vout the createrawtransaction RPC call requires
+# lx() takes *little-endian* hex and converts it to bytes; in Bitcoin
+# transaction hashes are shown little-endian rather than the usual big-endian.
+txid = lx('ace9dc7c987a52266e38fe8544c2d12182401341c98d151f4b394cf69aa5c3e5')
+vout = 0
+
+# Specify the amount send to your P2WSH address.
+amount = int(0.0001 * COIN)
+
+# Calculate an amount for the upcoming new UTXO. Set a high fee (5%) to bypass
+# bitcoind minfee setting.
+amount_less_fee = amount * 0.95
+
+# Create the txin structure, which includes the outpoint. The scriptSig
+# defaults to being empty as is necessary for spending a P2WSH output.
+txin = CMutableTxIn(COutPoint(txid, vout))
+
+
+# Specify a destination address and create the txout.
+destination_address = CBitcoinAddress(
+    '2NGZrVvZG92qGYqzTLjCAewvPZ7JE8S8VxE').to_scriptPubKey()
+txout = CMutableTxOut(amount_less_fee, destination_address)
+
+# Create the unsigned transaction.
+tx = CMutableTransaction([txin], [txout])
+
+# Calculate the signature hash for that transaction. Note how the script we use
+# is the witnessScript, not the redeemScript.
+sighash = SignatureHash(script=txin_witnessScript, txTo=tx, inIdx=0,
+                        hashtype=SIGHASH_ALL, amount=amount, sigversion=SIGVERSION_WITNESS_V0)
+
+# Now sign it. We have to append the type of signature we want to the end, in
+# this case the usual SIGHASH_ALL.
+sig = seckey.sign(sighash) + bytes([SIGHASH_ALL])
+
+
+# # Construct a witness for this P2WSH transaction and add to tx.
+witness = CScriptWitness([sig, txin_witnessScript])
+tx.wit = CTxWitness([CTxInWitness(witness)])
+
+# TODO: upgrade VerifyScript to support Segregated Witness and place verify the witness program here.
+
+# Done! Print the transaction to standard output with the bytes-to-hex
+# function.
+print(b2x(tx.serialize()))
+