amanrocks11

1. To check if the substring exists -> .find(sub_string) || .find(sub_string, start_pos, end_pos) Returns -1 if substring does not exists.
2. This method checks if all the characters of a string are alphanumeric (a-z, A-Z and 0-9). -> str.isalnum()
3. Swap cases. Will swap cases in the string. -> s.swapcase()
4. Join the string back -> string = ''.join(l) l can be any iteratable DS like a list.
5. This method checks if all the characters of a string are digits (0-9)/alphabetical (a-z and A-Z). -> str.isdigit() || str.isalpha()
6. This method checks if all the characters of a string are lowercase/uppercase characters -> str.islower() || **[str.isupper()](https://docs.python.org/2/library/stdtypes