Users 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'
VOTED = 'voted'
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,
        VOTED: 3
    }
CREATE_TABLE = 'CREATE TABLE IF NOT EXISTS '\
               +TABLE_NAME+'(id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL, '\
               +LOGIN+' varchar, '\
               +PASSWORD+' varchar, '+VOTED+' INTEGER)'
ADD_USER = "INSERT INTO "+TABLE_NAME+" ("+LOGIN+","+PASSWORD+","+VOTED+") VALUES ('%s','%s', 0)"
MARK_AS_VOTED = "UPDATE "+TABLE_NAME+" SET "+VOTED+" = 1 WHERE "+LOGIN+" = '%s'"
NULL_VOTES = "UPDATE "+TABLE_NAME+" SET "+VOTED+" = 0 WHERE "+ID+" = '%i'"

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)
    for row in c:
        if (login == row[TABLE_DICT[LOGIN]]):
            return False
    return True

def _str2hashstr_(string):
    tNumber = string
    hashObj = hashlib.sha256()
    byteArray = str.encode(string)
    hashObj.update(byteArray)
    return hashObj.hexdigest()

def _initDB_():
    conn = sqlite3.connect(DB_PATH)
    c = conn.cursor()
    c.execute(CREATE_TABLE)
    return (conn, c)

def _closeDB_(conn, c):
    conn.commit()
    c.close()
    conn.close()

def createAccount(login, password):
    if not _checkPassLength_(password):
        print(ERR_PASSWORD_TOO_SHORT)
        return False
    conn, c = _initDB_()
    if not _checkLoginUniqueness_(c, login):
        print(ERR_LOGIN_EXISTS)
        return False
    hash = _str2hashstr_(password)
    c.execute(ADD_USER%(login,hash))
    _closeDB_(conn, c)
    return True

def authentification(login, password):
    conn, c = _initDB_()
    # TODO: simplify the query
    c.execute("SELECT * FROM " + TABLE_NAME)
    for row in c:
        if login == row[TABLE_DICT[LOGIN]]:
            _closeDB_(conn, c)
            return _str2hashstr_(password) == row[TABLE_DICT[PASSWORD]]
    #print('Login not found!')
    _closeDB_(conn, c)

def markAsVoted(login):
    ret = False
    conn, c = _initDB_()
    # TODO: simplify the query
    c.execute("SELECT * FROM " + TABLE_NAME)
    for row in c:
        if row[TABLE_DICT[LOGIN]] == login:
            c.execute(MARK_AS_VOTED%login)
            ret = True
    _closeDB_(conn, c)
    return ret

def checkIfVoted(login):
    conn, c = _initDB_()
    # TODO: simplify the query
    c.execute("SELECT * FROM " + TABLE_NAME)
    for row in c:
        if row[TABLE_DICT[LOGIN]] == login:
            return bool(row[TABLE_DICT[VOTED]])
    _closeDB_(conn, c)

def nullVotes():
    conn, c = _initDB_()
    c.execute("SELECT * FROM " + TABLE_NAME)
    for row in c:
        c.execute(NULL_VOTES%row[TABLE_DICT[ID]])
    _closeDB_(conn, c)