User Data Base

#API to work with user login and password data base
import hashlib
import sqlite3

DB_PATH = 'C:\\Users\\user\\Desktop\\users.sqlite'
TABLE_NAME = 'users'
ID = 'id'
LOGIN = 'login'
PASSWORD = 'password'
ERR_PASSWORD_TOO_SHORT = 'Password is too short!'
ERR_LOGIN_EXISTS = 'Login already exists!'
MIN_PASS = 6
MAX_PASS = 20
TABLE_DICT = \
    {
        ID: 0,
        LOGIN: 1,
        PASSWORD: 2
    }
CREATE_TABLE = 'CREATE TABLE IF NOT EXISTS '\
               +TABLE_NAME+'(id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, '\
               +LOGIN+' varchar, '\
               +PASSWORD+' INTEGER)'
ADD_USER = "INSERT INTO "+TABLE_NAME+" ("+LOGIN+","+PASSWORD+") VALUES ('%s','%s')"

def _checkIfTableExists_(c):
    c.execute(CREATE_TABLE)

def _checkPassLength_(password):
    length = len(password)
    return length >= MIN_PASS or length <= MAX_PASS

def _checkLoginUniqueness_(c, login):
    # TODO: simplify the query
    c.execute("SELECT * FROM " + TABLE_NAME)
    row = c.fetchone()
    while row is not None:
        if (login == row[TABLE_DICT[LOGIN]]):
            return False
        row = c.fetchone()
    return True

def str2hashstr(string):
    tNumber = string
    hashObj = hashlib.sha256()
    byteArray = str.encode(string)
    hashObj.update(byteArray)
    return hashObj.hexdigest()

def createAccount(login, password):
    if not _checkPassLength_(password):
        print(ERR_PASSWORD_TOO_SHORT)
        return
    conn = sqlite3.connect(DB_PATH)
    c = conn.cursor()
    _checkIfTableExists_(c)
    if not _checkLoginUniqueness_(c, login):
        print(ERR_LOGIN_EXISTS)
        return
    hash = str2hashstr(password)

    c.execute(ADD_USER%(login,hash))
    conn.commit()
    c.close()
    conn.close()

def authentification(login, password):
    conn = sqlite3.connect(DB_PATH)
    c = conn.cursor()
    _checkIfTableExists_(c)
    # TODO: simplify the query
    c.execute("SELECT * FROM " + TABLE_NAME)
    row = c.fetchone()
    while row is not None:
        if login == row[TABLE_DICT[LOGIN]]:
            conn.commit()
            c.close()
            conn.close()
            return (str2hashstr(password) == row[TABLE_DICT[PASSWORD]])
        row = c.fetchone()
    #print('Login not found!')
    conn.commit()
    c.close()
    conn.close()