python password hashing

I simply made this for practice. But I want to know if it can be used in the realworld or not. Please point out any bad programming practices and how I can change them and look out for them next time. Your advice or tip will be the invaluable rain on my deadly isolated programming land.

import os
import hashlib
from base64 import b64encode, b64decode


def convert_to_bytes(value, value_name):
    if isinstance(value, str):
        return value.encode('UTF-8')
    else:
        raise ValueError('%s must be string or bytes' % value_name)


def derive_passhash(password, hash_name='sha512', salt=None, iterations=100000):
    '''This function returns str type password_hash.
    hash contains hash_name, iterations, salt, derived_key
    -> [hash_name] $ [iterations] $$ [salt] $s_k$ [derived_key] '''
    if salt is None:
        salt = os.urandom(32)
    if not isinstance(salt, bytes):
        salt = convert_to_bytes(salt, 'salt')
    if not isinstance(password, bytes):
        password = convert_to_bytes(password, 'password')
    if not isinstance(iterations, int):
        if isinstance(iterations, str) and iterations.isnumeric():
            iterations = int(iterations)
        else:
            print('iterations must be integer.')
            raise ValueError
    # derive passhash
    try:
        d_key = hashlib.pbkdf2_hmac(hash_name, password, salt, iterations)
        del password    # maybe it can help to make more secure?
    except ValueError as error:
        print('[!] Error cused %s' % error)
        # log(error)

    # put hash_name, salt, iterations and derived key together
    # and encode to base64 format.
    pre_v = '$'.join((hash_name, str(iterations))).encode('utf-8')
    end_v = b'$s_k$'.join((salt, d_key))
    total_value = b'$$'.join((pre_v, end_v))

    user_hash = b64encode(total_value).decode(encoding='utf-8')
    return user_hash


def check_password(user_hash, asserted_pw):
    if not isinstance(asserted_pw, bytes):
        asserted_pw = convert_to_bytes(asserted_pw, 'password')

    user_hash = b64decode(user_hash.encode('utf-8'))

    h_i, s_k = user_hash.split(b'$$')
    hash_name, iterations = h_i.decode('utf-8').split('$')
    salt, key = s_k.split(b'$s_k$')

    try:
        asserted_key = hashlib.pbkdf2_hmac(hash_name, asserted_pw,
                                           salt, int(iterations))
        del asserted_pw
    except ValueError as error:
        print('[!] Error cused %s' % error)

    if key == asserted_key:
        return True
    else:
        return False