How to check if file is empty or contains anything except an integer?

I want to open a file and check if in that file is an integer and if not write a 0.

I know how to write into a file and read a file, but to check if there is an integer and or there is something else, so I can replace it.

>Solution :

Alternative using .isdigit method of strings. It also tolerates new line \n at the end of the file by stripping it out.

with open("file","r") as fd:
    string = fd.read()
    if not string.strip().isdigit():
        with open("file","w") as fd:
            fd.write("0")