文章目录
《区块链编程》第五章
交易
交易的组成
- 版本号
- 输入
i. 父交易的id
ii. 父交易output的序号
iii. 签名脚本
iv. 序列号 - 输出
i. amount
ii. 公钥脚本 - 时间锁
练习1
p88
代码实现
from helper import little_endian_to_int
from io import BytesIO
class Tx:
def __init__(self, version, tx_ins, tx_outs, locktime, testnet=False):
self.version = version
self.tx_ins = tx_ins # <1>
self.tx_outs = tx_outs
self.locktime = locktime
self.testnet = testnet # <2>
def __repr__(self):
tx_ins = ''
for tx_in in self.tx_ins:
tx_ins += tx_in.__repr__() + '\n'
tx_outs = ''
for tx_out in self.tx_outs:
tx_outs += tx_out.__repr__() + '\n'
return 'tx: {}\nversion: {}\ntx_ins:\n{}tx_outs:\n{}locktime: {}'.format(
self.id(),
self.version,
tx_ins,
tx_outs,
self.locktime,
)
def id(self): # <3>
'''Human-readable hexadecimal of the transaction hash'''
return self.hash().hex()
def hash(self): # <4>
'''Binary hash of the legacy serialization'''
return hash256(self.serialize())[::-1]
# end::source1[]
@classmethod
def parse(cls, s, testnet=False):
'''Takes a byte stream and parses the transaction at the start
return a Tx object
'''
version = little_endian_to_int(s.read(4))
return cls(version, None, None, None, testnet=testnet)
if __name__ == '__main__':
tx = '01000000'
stream = BytesIO(bytes.fromhex(tx))
print(Tx.parse(stream).version)
测试
1
[Finished in 306ms]
练习2
p92
代码实现
# -*- coding: utf-8 -*-
# @Author: 从化北(喵星人)
# @Date: 2022-01-04 15:38:18
# @Last Modified by: 从化北
# @Last Modified time: 2022-01-04 16:33:55
from helper import little_endian_to_int, read_varint
from io import BytesIO
from script import Script
class Tx:
def __init__(self, version, tx_ins, tx_outs, locktime, testnet=False):
self.version = version
self.tx_ins = tx_ins #
self.tx_outs = tx_outs
self.locktime = locktime
self.testnet = testnet #
@classmethod
def parse(cls, s, testnet=False):
'''Takes a byte stream and parses the transaction at the start
return a Tx object
'''
# BytesIO的read会改变游标的位置。但不会更改BytesIO的数据
version = little_endian_to_int(s.read(4))
num_inputs = read_varint(s)
inputs = []
for _ in range(num_inputs):
inputs.append(TxIn.parse(s))
return cls(version, inputs, None, None, testnet=testnet)
class TxIn:
def __init__(self, prev_tx, prev_index, script_sig=None, sequence=0xffffffff):
self.prev_tx = prev_tx
self.prev_index = prev_index
if script_sig is None: # <1>
self.script_sig = Script()
else:
self.script_sig = script_sig
self.sequence = sequence
def __repr__(self):
return '{}:{}'.format(
self.prev_tx.hex(),
self.prev_index,
)
# end::source2[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_input at the start
return a TxIn object
'''
prev_tx = s.read(32)[::-1]
prev_index = little_endian_to_int(s.read(4))
script_sig = Script.parse(s)
sequence = little_endian_to_int(s.read(4))
return cls(prev_tx, prev_index, script_sig, sequence)
if __name__ == '__main__':
raw_tx = bytes.fromhex('0100000001813f79011acb80925dfe69b3def355fe914bd1d96a3f5f71bf8303c6a989c7d1000000006b483045022100ed81ff192e75a3fd2304004dcadb746fa5e24c5031ccfcf21320b0277457c98f02207a986d955c6e0cb35d446a89d3f56100f4d7f67801c31967743a9c8e10615bed01210349fc4e631e3624a545de3f89f5d8684c7b8138bd94bdd531d2e213bf016b278afeffffff02a135ef01000000001976a914bc3b654dca7e56b04dca18f2566cdaf02e8d9ada88ac99c39800000000001976a9141c4bc762dd5423e332166702cb75f40df79fea1288ac19430600')
stream = BytesIO(raw_tx)
tx = Tx.parse(stream)
print(tx.tx_ins)
测试
[d1c789a9c60383bf715f3f6ad9d14b91fe55f3deb369fe5d9280cb1a01793f81:0]
[Finished in 309ms]
练习3
p94
代码实现
# -*- coding: utf-8 -*-
# @Author: 从化北(喵星人)
# @Date: 2022-01-04 16:58:44
# @Last Modified by: 从化北
# @Last Modified time: 2022-01-04 17:03:18
from helper import little_endian_to_int, read_varint
from io import BytesIO
from script import Script
class Tx:
def __init__(self, version, tx_ins, tx_outs, locktime, testnet=False):
self.version = version
self.tx_ins = tx_ins #
self.tx_outs = tx_outs
self.locktime = locktime
self.testnet = testnet #
@classmethod
def parse(cls, s, testnet=False):
'''Takes a byte stream and parses the transaction at the start
return a Tx object
'''
# BytesIO的read会改变游标的位置。但不会更改BytesIO的数据
version = little_endian_to_int(s.read(4))
num_inputs = read_varint(s)
inputs = []
for _ in range(num_inputs):
inputs.append(TxIn.parse(s))
num_outputs = read_varint(s)
outputs = []
for _ in range(num_outputs):
outputs.append(TxOut.parse(s))
return cls(version, inputs, outputs, None, testnet=testnet)
class TxIn:
def __init__(self, prev_tx, prev_index, script_sig=None, sequence=0xffffffff):
self.prev_tx = prev_tx
self.prev_index = prev_index
if script_sig is None: # <1>
self.script_sig = Script()
else:
self.script_sig = script_sig
self.sequence = sequence
def __repr__(self):
return '{}:{}'.format(
self.prev_tx.hex(),
self.prev_index,
)
# end::source2[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_input at the start
return a TxIn object
'''
prev_tx = s.read(32)[::-1]
prev_index = little_endian_to_int(s.read(4))
script_sig = Script.parse(s)
sequence = little_endian_to_int(s.read(4))
return cls(prev_tx, prev_index, script_sig, sequence)
class TxOut:
def __init__(self, amount, script_pubkey):
self.amount = amount
self.script_pubkey = script_pubkey
def __repr__(self):
return '{}:{}'.format(self.amount, self.script_pubkey)
# end::source3[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_output at the start
return a TxOut object
'''
amount = little_endian_to_int(s.read(8))
script_pubkey = Script.parse(s)
return cls(amount, script_pubkey)
# amount is an integer in 8 bytes, little endian
# use Script.parse to get the ScriptPubKey
# return an instance of the class (see __init__ for args)
# raise NotImplementedError
# tag::source4[]
def serialize(self): # <1>
'''Returns the byte serialization of the transaction output'''
result = int_to_little_endian(self.amount, 8)
result += self.script_pubkey.serialize()
return result
# end::source4[]
if __name__ == '__main__':
raw_tx = bytes.fromhex('0100000001813f79011acb80925dfe69b3def355fe914bd1d96a3f5f71bf8303c6a989c7d1000000006b483045022100ed81ff192e75a3fd2304004dcadb746fa5e24c5031ccfcf21320b0277457c98f02207a986d955c6e0cb35d446a89d3f56100f4d7f67801c31967743a9c8e10615bed01210349fc4e631e3624a545de3f89f5d8684c7b8138bd94bdd531d2e213bf016b278afeffffff02a135ef01000000001976a914bc3b654dca7e56b04dca18f2566cdaf02e8d9ada88ac99c39800000000001976a9141c4bc762dd5423e332166702cb75f40df79fea1288ac19430600')
stream = BytesIO(raw_tx)
tx = Tx.parse(stream)
# print(tx.tx_ins)
print(tx.tx_outs)
测试
[32454049:OP_DUP OP_HASH160 bc3b654dca7e56b04dca18f2566cdaf02e8d9ada OP_EQUALVERIFY OP_CHECKSIG, 10011545:OP_DUP OP_HASH160 1c4bc762dd5423e332166702cb75f40df79fea12 OP_EQUALVERIFY OP_CHECKSIG]
[Finished in 319ms]
练习4
p95
代码实现
# -*- coding: utf-8 -*-
# @Author: 从化北(喵星人)
# @Date: 2022-01-04 17:04:41
# @Last Modified by: 从化北
# @Last Modified time: 2022-01-04 17:05:35
from helper import little_endian_to_int, read_varint
from io import BytesIO
from script import Script
class Tx:
def __init__(self, version, tx_ins, tx_outs, locktime, testnet=False):
self.version = version
self.tx_ins = tx_ins #
self.tx_outs = tx_outs
self.locktime = locktime
self.testnet = testnet #
@classmethod
def parse(cls, s, testnet=False):
'''Takes a byte stream and parses the transaction at the start
return a Tx object
'''
# BytesIO的read会改变游标的位置。但不会更改BytesIO的数据
version = little_endian_to_int(s.read(4))
num_inputs = read_varint(s)
inputs = []
for _ in range(num_inputs):
inputs.append(TxIn.parse(s))
num_outputs = read_varint(s)
outputs = []
for _ in range(num_outputs):
outputs.append(TxOut.parse(s))
locktime = little_endian_to_int(s.read(4))
return cls(version, inputs, outputs, locktime, testnet=testnet)
class TxIn:
def __init__(self, prev_tx, prev_index, script_sig=None, sequence=0xffffffff):
self.prev_tx = prev_tx
self.prev_index = prev_index
if script_sig is None: # <1>
self.script_sig = Script()
else:
self.script_sig = script_sig
self.sequence = sequence
def __repr__(self):
return '{}:{}'.format(
self.prev_tx.hex(),
self.prev_index,
)
# end::source2[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_input at the start
return a TxIn object
'''
prev_tx = s.read(32)[::-1]
prev_index = little_endian_to_int(s.read(4))
script_sig = Script.parse(s)
sequence = little_endian_to_int(s.read(4))
return cls(prev_tx, prev_index, script_sig, sequence)
class TxOut:
def __init__(self, amount, script_pubkey):
self.amount = amount
self.script_pubkey = script_pubkey
def __repr__(self):
return '{}:{}'.format(self.amount, self.script_pubkey)
# end::source3[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_output at the start
return a TxOut object
'''
amount = little_endian_to_int(s.read(8))
script_pubkey = Script.parse(s)
return cls(amount, script_pubkey)
# amount is an integer in 8 bytes, little endian
# use Script.parse to get the ScriptPubKey
# return an instance of the class (see __init__ for args)
# raise NotImplementedError
# tag::source4[]
def serialize(self): # <1>
'''Returns the byte serialization of the transaction output'''
result = int_to_little_endian(self.amount, 8)
result += self.script_pubkey.serialize()
return result
# end::source4[]
if __name__ == '__main__':
raw_tx = bytes.fromhex('0100000001813f79011acb80925dfe69b3def355fe914bd1d96a3f5f71bf8303c6a989c7d1000000006b483045022100ed81ff192e75a3fd2304004dcadb746fa5e24c5031ccfcf21320b0277457c98f02207a986d955c6e0cb35d446a89d3f56100f4d7f67801c31967743a9c8e10615bed01210349fc4e631e3624a545de3f89f5d8684c7b8138bd94bdd531d2e213bf016b278afeffffff02a135ef01000000001976a914bc3b654dca7e56b04dca18f2566cdaf02e8d9ada88ac99c39800000000001976a9141c4bc762dd5423e332166702cb75f40df79fea1288ac19430600')
stream = BytesIO(raw_tx)
tx = Tx.parse(stream)
# print(tx.tx_ins)
print(tx.locktime)
运行结果
410393
[Finished in 320ms]
练习5
p95
代码实现
# -*- coding: utf-8 -*-
# @Author: 从化北(喵星人)
# @Date: 2022-01-04 17:06:15
# @Last Modified by: 从化北
# @Last Modified time: 2022-01-04 17:11:16
from helper import little_endian_to_int, read_varint
from io import BytesIO
from script import Script
class Tx:
def __init__(self, version, tx_ins, tx_outs, locktime, testnet=False):
self.version = version
self.tx_ins = tx_ins #
self.tx_outs = tx_outs
self.locktime = locktime
self.testnet = testnet #
@classmethod
def parse(cls, s, testnet=False):
'''Takes a byte stream and parses the transaction at the start
return a Tx object
'''
# BytesIO的read会改变游标的位置。但不会更改BytesIO的数据
version = little_endian_to_int(s.read(4))
num_inputs = read_varint(s)
inputs = []
for _ in range(num_inputs):
inputs.append(TxIn.parse(s))
num_outputs = read_varint(s)
outputs = []
for _ in range(num_outputs):
outputs.append(TxOut.parse(s))
locktime = little_endian_to_int(s.read(4))
return cls(version, inputs, outputs, locktime, testnet=testnet)
class TxIn:
def __init__(self, prev_tx, prev_index, script_sig=None, sequence=0xffffffff):
self.prev_tx = prev_tx
self.prev_index = prev_index
if script_sig is None: # <1>
self.script_sig = Script()
else:
self.script_sig = script_sig
self.sequence = sequence
def __repr__(self):
return '{}:{}'.format(
self.prev_tx.hex(),
self.prev_index,
)
# end::source2[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_input at the start
return a TxIn object
'''
prev_tx = s.read(32)[::-1]
prev_index = little_endian_to_int(s.read(4))
script_sig = Script.parse(s)
sequence = little_endian_to_int(s.read(4))
return cls(prev_tx, prev_index, script_sig, sequence)
class TxOut:
def __init__(self, amount, script_pubkey):
self.amount = amount
self.script_pubkey = script_pubkey
def __repr__(self):
return '{}:{}'.format(self.amount, self.script_pubkey)
# end::source3[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_output at the start
return a TxOut object
'''
amount = little_endian_to_int(s.read(8))
script_pubkey = Script.parse(s)
return cls(amount, script_pubkey)
# amount is an integer in 8 bytes, little endian
# use Script.parse to get the ScriptPubKey
# return an instance of the class (see __init__ for args)
# raise NotImplementedError
# tag::source4[]
def serialize(self): # <1>
'''Returns the byte serialization of the transaction output'''
result = int_to_little_endian(self.amount, 8)
result += self.script_pubkey.serialize()
return result
# end::source4[]
if __name__ == '__main__':
raw_tx = bytes.fromhex('010000000456919960ac691763688d3d3bcea9ad6ecaf875df5339e\
148a1fc61c6ed7a069e010000006a47304402204585bcdef85e6b1c6af5c2669d4830ff86e42dd\
205c0e089bc2a821657e951c002201024a10366077f87d6bce1f7100ad8cfa8a064b39d4e8fe4e\
a13a7b71aa8180f012102f0da57e85eec2934a82a585ea337ce2f4998b50ae699dd79f5880e253\
dafafb7feffffffeb8f51f4038dc17e6313cf831d4f02281c2a468bde0fafd37f1bf882729e7fd\
3000000006a47304402207899531a52d59a6de200179928ca900254a36b8dff8bb75f5f5d71b1c\
dc26125022008b422690b8461cb52c3cc30330b23d574351872b7c361e9aae3649071c1a716012\
1035d5c93d9ac96881f19ba1f686f15f009ded7c62efe85a872e6a19b43c15a2937feffffff567\
bf40595119d1bb8a3037c356efd56170b64cbcc160fb028fa10704b45d775000000006a4730440\
2204c7c7818424c7f7911da6cddc59655a70af1cb5eaf17c69dadbfc74ffa0b662f02207599e08\
bc8023693ad4e9527dc42c34210f7a7d1d1ddfc8492b654a11e7620a0012102158b46fbdff65d0\
172b7989aec8850aa0dae49abfb84c81ae6e5b251a58ace5cfeffffffd63a5e6c16e620f86f375\
925b21cabaf736c779f88fd04dcad51d26690f7f345010000006a47304402200633ea0d3314bea\
0d95b3cd8dadb2ef79ea8331ffe1e61f762c0f6daea0fabde022029f23b3e9c30f080446150b23\
852028751635dcee2be669c2a1686a4b5edf304012103ffd6f4a67e94aba353a00882e563ff272\
2eb4cff0ad6006e86ee20dfe7520d55feffffff0251430f00000000001976a914ab0c0b2e98b1a\
b6dbf67d4750b0a56244948a87988ac005a6202000000001976a9143c82d7df364eb6c75be8c80\
df2b3eda8db57397088ac46430600')
stream = BytesIO(raw_tx)
tx = Tx.parse(stream)
# print(tx.tx_ins)
print("第二个input的签名脚本：")
print(tx.tx_ins[1].script_sig)
print("第一个output的公钥脚本：")
print(tx.tx_outs[0].script_pubkey)
print("第二个output的数量：")
print(tx.tx_outs[1].amount)
运行结果
第二个input的签名脚本：
304402207899531a52d59a6de200179928ca900254a36b8dff8bb75f5f5d71b1cdc26125022008b422690b8461cb52c3cc30330b23d574351872b7c361e9aae3649071c1a71601 035d5c93d9ac96881f19ba1f686f15f009ded7c62efe85a872e6a19b43c15a2937
第一个output的公钥脚本：
OP_DUP OP_HASH160 ab0c0b2e98b1ab6dbf67d4750b0a56244948a879 OP_EQUALVERIFY OP_CHECKSIG
第二个output的数量：
40000000
[Finished in 319ms]
练习6
p98
代码实现
# -*- coding: utf-8 -*-
# @Author: 从化北(喵星人)
# @Date: 2022-01-04 17:12:19
# @Last Modified by: 从化北
# @Last Modified time: 2022-01-04 17:15:35
class Tx:
...
def fee(self, testnet=False):
input_sum, output_sum = 0, 0
for tx_in in self.tx_ins:
input_sum += tx_in.value(testnet=testnet)
for tx_out in self.tx_outs:
output_sum += tx_out.amount
return input_sum - output_sum
运行结果
这部分的fee不给测试了。
无
本章中涉及的tx完整代码
书中给的tx
from io import BytesIO
from unittest import TestCase
import json
import requests
from helper import (
encode_varint,
hash256,
int_to_little_endian,
little_endian_to_int,
read_varint,
run,
)
from script import Script
# tag::source7[]
class TxFetcher:
cache = {
}
@classmethod
def get_url(cls, testnet=False):
if testnet:
return 'https://blockstream.info/testnet/api/'
else:
return 'https://blockstream.info/api/'
@classmethod
def fetch(cls, tx_id, testnet=False, fresh=False):
if fresh or (tx_id not in cls.cache):
url = '{}/tx/{}/hex'.format(cls.get_url(testnet), tx_id)
response = requests.get(url)
try:
raw = bytes.fromhex(response.text.strip())
except ValueError:
raise ValueError('unexpected response: {}'.format(response.text))
if raw[4] == 0:
raw = raw[:4] + raw[6:]
tx = Tx.parse(BytesIO(raw), testnet=testnet)
tx.locktime = little_endian_to_int(raw[-4:])
else:
tx = Tx.parse(BytesIO(raw), testnet=testnet)
if tx.id() != tx_id: # <1>
raise ValueError('not the same id: {} vs {}'.format(tx.id(),
tx_id))
cls.cache[tx_id] = tx
cls.cache[tx_id].testnet = testnet
return cls.cache[tx_id]
# end::source7[]
@classmethod
def load_cache(cls, filename):
disk_cache = json.loads(open(filename, 'r').read())
for k, raw_hex in disk_cache.items():
raw = bytes.fromhex(raw_hex)
if raw[4] == 0:
raw = raw[:4] + raw[6:]
tx = Tx.parse(BytesIO(raw))
tx.locktime = little_endian_to_int(raw[-4:])
else:
tx = Tx.parse(BytesIO(raw))
cls.cache[k] = tx
@classmethod
def dump_cache(cls, filename):
with open(filename, 'w') as f:
to_dump = {
k: tx.serialize().hex() for k, tx in cls.cache.items()}
s = json.dumps(to_dump, sort_keys=True, indent=4)
f.write(s)
# tag::source1[]
class Tx:
def __init__(self, version, tx_ins, tx_outs, locktime, testnet=False):
self.version = version
self.tx_ins = tx_ins # <1>
self.tx_outs = tx_outs
self.locktime = locktime
self.testnet = testnet # <2>
def __repr__(self):
tx_ins = ''
for tx_in in self.tx_ins:
tx_ins += tx_in.__repr__() + '\n'
tx_outs = ''
for tx_out in self.tx_outs:
tx_outs += tx_out.__repr__() + '\n'
return 'tx: {}\nversion: {}\ntx_ins:\n{}tx_outs:\n{}locktime: {}'.format(
self.id(),
self.version,
tx_ins,
tx_outs,
self.locktime,
)
def id(self): # <3>
'''Human-readable hexadecimal of the transaction hash'''
return self.hash().hex()
def hash(self): # <4>
'''Binary hash of the legacy serialization'''
return hash256(self.serialize())[::-1]
# end::source1[]
@classmethod
def parse(cls, s, testnet=False):
'''Takes a byte stream and parses the transaction at the start
return a Tx object
'''
version = little_endian_to_int(s.read(4))
num_inputs = read_varint(s)
inputs = []
for _ in range(num_inputs):
inputs.append(TxIn.parse(s))
num_outputs = read_varint(s)
outputs = []
for _ in range(num_outputs):
outputs.append(TxOut.parse(s))
locktime = little_endian_to_int(s.read(4))
return cls(version, inputs, outputs, locktime, testnet=testnet)
# s.read(n) will return n bytes
# version is an integer in 4 bytes, little-endian
# num_inputs is a varint, use read_varint(s)
# parse num_inputs number of TxIns
# num_outputs is a varint, use read_varint(s)
# parse num_outputs number of TxOuts
# locktime is an integer in 4 bytes, little-endian
# return an instance of the class (see __init__ for args)
# raise NotImplementedError
# tag::source6[]
def serialize(self):
'''Returns the byte serialization of the transaction'''
result = int_to_little_endian(self.version, 4)
result += encode_varint(len(self.tx_ins))
for tx_in in self.tx_ins:
result += tx_in.serialize()
result += encode_varint(len(self.tx_outs))
for tx_out in self.tx_outs:
result += tx_out.serialize()
result += int_to_little_endian(self.locktime, 4)
return result
# end::source6[]
def fee(self):
'''Returns the fee of this transaction in satoshi'''
# initialize input sum and output sum
# use TxIn.value() to sum up the input amounts
# use TxOut.amount to sum up the output amounts
# fee is input sum - output sum
input_sum, output_sum = 0, 0
for tx_in in self.tx_ins:
input_sum += tx_in.value(testnet=testnet)
for tx_out in self.tx_outs:
output_sum += tx_out.amount
return input_sum - output_sum
# tag::source2[]
class TxIn:
def __init__(self, prev_tx, prev_index, script_sig=None, sequence=0xffffffff):
self.prev_tx = prev_tx
self.prev_index = prev_index
if script_sig is None: # <1>
self.script_sig = Script()
else:
self.script_sig = script_sig
self.sequence = sequence
def __repr__(self):
return '{}:{}'.format(
self.prev_tx.hex(),
self.prev_index,
)
# end::source2[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_input at the start
return a TxIn object
'''
prev_tx = s.read(32)[::-1]
prev_index = little_endian_to_int(s.read(4))
script_sig = Script.parse(s)
sequence = little_endian_to_int(s.read(4))
return cls(prev_tx, prev_index, script_sig, sequence)
# prev_tx is 32 bytes, little endian
# prev_index is an integer in 4 bytes, little endian
# use Script.parse to get the ScriptSig
# sequence is an integer in 4 bytes, little-endian
# return an instance of the class (see __init__ for args)
# raise NotImplementedError
# tag::source5[]
def serialize(self):
'''Returns the byte serialization of the transaction input'''
result = self.prev_tx[::-1]
result += int_to_little_endian(self.prev_index, 4)
result += self.script_sig.serialize()
result += int_to_little_endian(self.sequence, 4)
return result
# end::source5[]
# tag::source8[]
def fetch_tx(self, testnet=False):
return TxFetcher.fetch(self.prev_tx.hex(), testnet=testnet)
def value(self, testnet=False):
'''Get the output value by looking up the tx hash.
Returns the amount in satoshi.
'''
tx = self.fetch_tx(testnet=testnet)
return tx.tx_outs[self.prev_index].amount
def script_pubkey(self, testnet=False):
'''Get the ScriptPubKey by looking up the tx hash.
Returns a Script object.
'''
tx = self.fetch_tx(testnet=testnet)
return tx.tx_outs[self.prev_index].script_pubkey
# end::source8[]
# tag::source3[]
class TxOut:
def __init__(self, amount, script_pubkey):
self.amount = amount
self.script_pubkey = script_pubkey
def __repr__(self):
return '{}:{}'.format(self.amount, self.script_pubkey)
# end::source3[]
@classmethod
def parse(cls, s):
'''Takes a byte stream and parses the tx_output at the start
return a TxOut object
'''
amount = little_endian_to_int(s.read(8))
script_pubkey = Script.parse(s)
return cls(amount, script_pubkey)
# amount is an integer in 8 bytes, little endian
# use Script.parse to get the ScriptPubKey
# return an instance of the class (see __init__ for args)
raise NotImplementedError
# tag::source4[]
def serialize(self): # <1>
'''Returns the byte serialization of the transaction output'''
result = int_to_little_endian(self.amount, 8)
result += self.script_pubkey.serialize()
return result
# end::source4[]