Convert testnet private key to mainnet private key in Bitcoin

tn2mn.py

#!/usr/bin/env python
import base58
import hashlib

main = bytes([128])
test = bytes([239])

def decodeSecret(key, network):
    assert isinstance(network, bytes), network
    k = base58.b58decode_check(key)
    len_correct = len(k) == 32 + len(network) or (len(k) == 33 + len(network) and k[-1] == 1)
    assert len_correct, "Bad length: {}".format(len(k))
    prefix_ok = k[0:1] == network
    assert prefix_ok, "Bad prefix: {}. Expected {}".format(k[0:1], network)
    is_compressed = len(k) == 33 + len(network)
    return k[len(network):len(network) + 32], is_compressed

def encode_secret(key, network, is_compressed):
    assert isinstance(network, bytes), network
    out = bytearray([])
    out += network
    out += key
    if is_compressed:
        out += bytes([1])
    assert len(out) <= 34, len(out)
    ret = base58.b58encode_check(out)
    return ret

def tn2mn(key):
    data, compressed = decodeSecret(key, test)
    return encode_secret(data, main, compressed)

    
tn = "cViwbQfYbBvaKuh4wAPTrTWLXAwyLn2PudoNAkua6VWaoHtyQPSN"
mn = tn2mn(tn)
print("vbitcoin-cli importprivkey {}".format(mn.decode('ascii')))