text: #!/usr/bin/env python3
  # Copyright (c) 2019 The ReBitcoin Core developers
  # Distributed under the MIT software license, see the accompanying
  # file COPYING or http://www.opensource.org/licenses/mit-license.php.
  """Useful Script constants and utils."""
  from test_framework.script import CScript
  
  # To prevent a "tx-size-small" policy rule error, a transaction has to have a
  # non-witness size of at least 82 bytes (MIN_STANDARD_TX_NONWITNESS_SIZE in
  # src/policy/policy.h). Considering a Tx with the smallest possible single
  # input (blank, empty scriptSig), and with an output omitting the scriptPubKey,
  # we get to a minimum size of 60 bytes:
  #
  # Tx Skeleton: 4 [Version] + 1 [InCount] + 1 [OutCount] + 4 [LockTime] = 10 bytes
  # Blank Input: 32 [PrevTxHash] + 4 [Index] + 1 [scriptSigLen] + 4 [SeqNo] = 41 bytes
  # Output:      8 [Amount] + 1 [scriptPubKeyLen] = 9 bytes
  #
  # Hence, the scriptPubKey of the single output has to have a size of at
  # least 22 bytes, which corresponds to the size of a P2WPKH scriptPubKey.
  # The following script constant consists of a single push of 21 bytes of 'a':
  #   <PUSH_21> <21-bytes of 'a'>
  # resulting in a 22-byte size. It should be used whenever (small) fake
  # scriptPubKeys are needed, to guarantee that the minimum transaction size is
  # met.
  DUMMY_P2WPKH_SCRIPT = CScript([b'a' * 21])
  