You should write [PEP8][1] conformant code. See http://pep8online.com/ to check your code.

Try

    #!/usr/bin/env python

    numbers = []

    while True:
        inp = raw_input("Enter a number: ")
        if inp == 'done':
            break
        numbers.append(int(inp))
        if len(inp) < 1:
            print("hey")
            break

        try:
            num = float(inp)
        except:
            print("Invalid input")
            continue

    if len(numbers) == 0:
        print("No number entered")
    else:
        print("Maximum is %i" % max(numbers))
        print("Minimum is %i" % min(numbers))


  [1]: https://www.python.org/dev/peps/pep-0008