how to fix if-else problem in calling functions in python?

if file is not None:
        content = file.readlines()
        if 'I'  and 'J' in content:
            display_oval()
        else:
            display_polygon()

in this case,suppose i opened a file containing I&J . i expect to call display_oval() but it calls display_polygon(). when i opened file not containing I&J,display_polygon() calls as expected. when i replaced 'I' and 'J'with 'I' or 'J',when i opened a file containing I&J,display_oval() works fine. But when i opened file not containing I&J, nothing works. I want to call display_oval()if file contains I&J and display_polygon()otherwise. how it can be done?