import io

with open("out.txt", "w+") as fo:
    fo.write("one\n")
    fo.write("two\n")
    fo.write("three four five\n")

    current_position = fo.seek(500, io.SEEK_SET)
    print(current_position)

# The opened file length is less then 500, and where we set the curser as above.
# Python fill all places with null,To my opinion Should Throw compatible Exception
# But if we write       current_position = fo.seek(5, io.SEEK_End), An Exception will raise