>>> current_users = ['YarosLav', 'MiSha', 'GrishA', 'MAsha', 'LilyA']
>>> current_users_lower = [user.lower() for user in current_users]
>>> current_users
['YarosLav', 'MiSha', 'GrishA', 'MAsha', 'LilyA']
>>> current_users_lower
['yaroslav', 'misha', 'grisha', 'masha', 'lilya']