Python proof of work example from Mastering Bitcoin

proof_of_work.py

import hashlib
import time

max_nonce = 2 ** 32 # 4 billion

def proof_of_work(header, difficulty_bits):

    # calculate the difficulty target
    target = 2 ** (256-difficulty_bits)

    for nonce in range(max_nonce):
        hash_result = hashlib.sha256(
            (str(header)+str(nonce)).encode()
        ).hexdigest()

        # check if this is a valid result, below the target
        if int(hash_result, 16) < target:
            print(f"Success with nonce {nonce}")
            print(f"Hash is {hash_result}")
            return (hash_result,nonce)

    print(f"Failed after {nonce} (max_nonce) tries")
    return nonce


if __name__ == "__main__":

    nonce = 0
    hash_result = ''

    # difficulty from 0 to 31 bits
    original_max_range = 32
    test_range = 3
    for difficulty_bits in range(test_range):

        difficulty = 2 ** difficulty_bits
        print(f"\nDifficulty: {difficulty} ({difficulty_bits} bits)")

        print("Starting search...")

        # checkpoint the current time
        start_time = time.time()

        # make a new block which includes the hash from the previous block
        # we fake a block of transactions - just a string
        new_block = "test block with transactions" + hash_result

        # find a valid nonce for the new block
        (hash_result, nonce) = proof_of_work(new_block, difficulty_bits)

        # checkpoint how long it took to find a result
        end_time = time.time()

        elapsed_time = end_time - start_time
        print(f"Elapsed Time: {elapsed_time:4f} seconds")

        if elapsed_time > 0:

            # estimate the hashes per second
            hash_power = float(int(nonce)/elapsed_time)
            print(f"Hashing Power: {hash_power} hashes per second")

What is the difficulty bits imply ?

Python 3 version:

import hashlib
import time

max_nonce = 2 ** 32 # 4 billion

def proof_of_work(header, difficulty_bits):

    # calculate the difficulty target
    target = 2 ** (256-difficulty_bits)

    for nonce in range(max_nonce):
        hash_result = hashlib.sha256(
            (str(header)+str(nonce)).encode()
        ).hexdigest()

        # check if this is a valid result, below the target
        if int(hash_result, 16) < target:
            print(f"Success with nonce {nonce}")
            print(f"Hash is {hash_result}")
            return (hash_result,nonce)

    print(f"Failed after {nonce} (max_nonce) tries")
    return nonce


if __name__ == "__main__":

    nonce = 0
    hash_result = ''

    # difficulty from 0 to 31 bits
    original_max_range = 32
    test_range = 32
    for difficulty_bits in range(test_range):

        difficulty = 2 ** difficulty_bits
        print(f"\nDifficulty: {difficulty} ({difficulty_bits} bits)")

        print("Starting search...")

        # checkpoint the current time
        start_time = time.time()

        # make a new block which includes the hash from the previous block
        # we fake a block of transactions - just a string
        new_block = "test block with transactions" + hash_result

        # find a valid nonce for the new block
        (hash_result, nonce) = proof_of_work(new_block, difficulty_bits)

        # checkpoint how long it took to find a result
        end_time = time.time()

        elapsed_time = end_time - start_time
        print(f"Elapsed Time: {elapsed_time:4f} seconds")

        if elapsed_time > 0:

            # estimate the hashes per second
            hash_power = float(int(nonce)/elapsed_time)
            print(f"Hashing Power: {hash_power} hashes per second")

I forgot I posted this. Thanks for the update.