lineinfile ansible module skips a line

[madha...@gmail.com]

I just posted my question on stackoverflow. Figured I will post here as well in hopes someone here can help.

http://stackoverflow.com/questions/43683862/lineinfile-ansible-module-skips-a-line

content:

I have a need to know the index of host names in the inventory. I am using the below code to create a variable file that I can use in a subsequent play book

- name: Debug me
  hosts: hosts
  tasks:
      - debug: msg="{{ inventory_hostname }}"
      - debug: msg="{{ play_hosts.index(inventory_hostname) }}"
      - local_action: 'lineinfile create=yes dest=/tmp/test.conf
                   line="host{{ play_hosts.index(inventory_hostname) }}=
                   {{ inventory_hostname }}"'

I have the following inventory file

[hosts]
my.host1.com
my.host2.com

Now when I run this, the test.conf that gets generated under /tmp sometimes has both hostnames like this

host1= my.host2.com
host0= my.host1.com

when I run the same playbook a few times each time emptying the test.conf before running. quite a few times the file only has one entry

host1= my.host2.com

or

host0= my.host1.com

how come the same ansible playbook behaving differently? Please help. As you probably can already tell, I am new to ansible and trying from different examples that I have found online.