ctype These functions check whether a character or string falls into a certain character class according to the i current locale. When called with an integer argument these functions behave exactly like their C counterparts. When called with a string argument they will check every character in the string and will only return true if every character in the string matches the requested criteria. Passing anything else but a string or integer will return false immediately. isalnum Check for alphanumeric character(s) bool isalnum string c See also setlocale. isalpha bool isalpha string c iscntrl bool iscntrl string c isdigit bool isdigit string c islower bool islower string c isgraph bool isgraph string c isprint bool isprint string c ispunct bool ispunct string c isspace bool isspace string c isupper bool isupper string c isxdigit bool isxdigit string c