def is_allowed_specific_char(string):
    import re
    
    get_char = re.compile(r'[^a-zA-Z0-9.]')
    string = get_char.search(string)
    return not bool(string)
def is_allowed_specific_char(char):
    import re
   
    get_char = re.compile(r"[^a-zA-Z0-9.]")
    char = get_char.search(char)
    return not bool(char)