[ansible] Check via the yum module and a registered value if a package is installed or not

pkg.yml

---
- name: Ansible tests playbook
  hosts: all
  remote_user: root

  tasks:
    - name: Check if mariadb-libs-5.5.44-2.el7.centos.x86_64 package is installed
      yum:
        list=mariadb-libs-5.5*x86_64
      register: pkg

    - name: Removing old mariadb-libs package 
      package:
        name=mariadb-libs
        state=absent
      when: ansible_os_family == 'RedHat' and
            pkg.results[0].yumstate == 'installed'

This works better:

pkg.results|selectattr("yumstate", "match", "installed")|list|length != 0

I am using the code suggested by CrusaderX and I am getting the below error:
The error was: error while evaluating conditional ((is_installed.results|length == 1) or (is_installed.results[1].yumstate != 'installed')): list object has no element 1

I am running on Redhat 7.1

disable SELINUX and firewall and try

@beebird solution is cleanest

- name: Check if rpm is already installed
  yum:
    list: my-rpm
  # If not installed yum_list.results[*].yumstate != installed
  register: yum_list

- name: Conditionally do next thing
  debug:
    msg: "Not installed"
  when: yum_list.results | selectattr("yumstate", "match", "installed") | list | length == 0

the package_facts module maybe better for this.

  - package_facts: {}
  - when: ansible_facts.packages["mysql57-community-release"] is undefined
    block:
    - yum:
        name: http://repo.mysql.com/mysql57-community-release-el7-10.noarch.rpm
        state: present
    - yum: {name: mysql-server, state: present}
    - service: {name: mysqld, state: started, enabled: yes}
    - shell: grep 'temporary password' /var/log/mysqld.log | awk '{print $NF}';
      register: result
    - .... etc ...