Some questions

Hello, i new in this forum and i happy to join here !
I want to ask you some questions please:
1) How can i check if string had only letters ?
2) How can i check if string has only numbers ?
3) How can i check if string is good mail ?
4) If i want to built a little program that delete all the files from
the computer, you recommend me to programing this program
in Python, or in other language ?

Thanks you .

1. .isalpha()
2. .isdigit()
3. I'm not sure what is "good" but if you want to see if there's an "@" and it's not the first or last character: "@" in <string>[1:-2]
4. depending on the operating system, it's probably simpler in the native script (DOS, BASH, etc.)