How to make Ansible execute a shell script if a package is not installed

Question

How can I make Ansible execute a shell script if a (rpm) package is not installed? Is it somehow possible to leverage the yum module?

Answer 1

Based on the Bruce P answer above, a similar approach for apt/deb files is

- name: Check if foo is installed
  command: dpkg-query -l foo
  register: deb_check

- name: Execute script if foo is not installed
  command: somescript
  when: deb_check.stdout.find('no packages found') != -1