# Running python command on when statement

**URL:** <https://forum.ansible.com/t/running-python-command-on-when-statement/14932>\
**Category:** Ansible Project\
**Created:** [April 3, 2014, 12:25pm UTC](https://forum.ansible.com/t/running-python-command-on-when-statement/14932 "2014-04-03T12:25:37Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![douglaslopespereira](https://avatars.discourse-cdn.com/v4/letter/d/a87d85/32.png) [@douglaslopespereira](https://forum.ansible.com/u/douglaslopespereira)\
**Post date:** [April 3, 2014, 12:25pm UTC](https://forum.ansible.com/t/running-python-command-on-when-statement/14932/1 "2014-04-03T12:25:37Z")

</div>

Hi all,

I was trying to update ansible from 1.2 to 1.5 and noticed that I can no longer use “only\_if” which has been replaced by “when”.

But when I try to run a shell task with this condition:

when: “len(filter(lambda m: m[‘mount’] == ‘/var/lib/myMount’, ‘{{ansible\_mounts}}’)) == 0”

I get the following error:

error while evaluating conditional: len(filter(lambda m: m[‘mount’] == ‘/var/lib/myMount’, ‘[{u’size\_total’: 8455118848, u’mount’: u’/‘, u’size\_available’: 6891151360, u’fstype’: u’ext4’, u’device’: u’/dev/xvda1’, u’options’: u’rw’}, {u’size\_total’: 16122802176, u’mount’: u’/mnt’, u’size\_available’: 15129432064, u’fstype’: u’ext3’, u’device’: u’/dev/xvdb’, u’options’: u’rw,\_netdev’}, {u’size\_total’: 107321753600, u’mount’: u’/var/lib/myMount’, u’size\_available’: 107250851840, u’fstype’: u’xfs’, u’device’: u’/dev/xvdf’, u’options’: u’rw,noatime’}]')) == 0

The ansible\_mounts variable is being correctly returned as you can see in the error message.

I’ve tryed different combinations of positioning the quote marks but no luck.

Any help?

Regards,  
Douglas

---

<div class="post-metadata">

**Author:** ![sivel](https://sea1.discourse-cdn.com/ansible/user_avatar/forum.ansible.com/sivel/32/1198_2.png) [@sivel](https://forum.ansible.com/u/sivel)\
**Post date:** [April 4, 2014, 12:16pm UTC](https://forum.ansible.com/t/running-python-command-on-when-statement/14932/2 "2014-04-04T12:16:19Z")

</div>

Douglas,

You won’t be able to use pure python in a when statement, you will have to handle it using jinja2.

I see 2 options for you:

1. Use a combination of several jinja2 filters to get you what you want such as:

when: ansible\_mounts|map(attribute=‘mount’)|intersect([‘/var/lib/myMount’])|length == 0

1. Create your own custom jinja2 filter to do this.

---

<div class="post-metadata">

**Author:** ![douglaslopespereira](https://avatars.discourse-cdn.com/v4/letter/d/a87d85/32.png) [@douglaslopespereira](https://forum.ansible.com/u/douglaslopespereira)\
**Post date:** [April 4, 2014, 1:02pm UTC](https://forum.ansible.com/t/running-python-command-on-when-statement/14932/3 "2014-04-04T13:02:56Z")

</div>

Hi Matt,

That is a great suggestion! I will give it a try.

I overcame this by using this task:

- name: check mount point  
shell: mount | sed -n -e ‘//var/lib/myMount.\*/p’  
register: result

and after that using the result variable on the when statement:

when: result.stdout==“”

It looks like your solution is more straightforward.

Thank you.  
Regards,  
Douglas

---

<div class="post-metadata">

**Author:** ![Michael\_DeHaan1](https://avatars.discourse-cdn.com/v4/letter/m/5e9695/32.png) [@Michael\_DeHaan1](https://forum.ansible.com/u/Michael_DeHaan1)\
**Post date:** [April 4, 2014, 3:19pm UTC](https://forum.ansible.com/t/running-python-command-on-when-statement/14932/4 "2014-04-04T15:19:25Z")

</div>

I should point out that trying to code in playbooks is usually the sign that you’re trying too hard to do something.

It should almost always be thought of as “what is the easier way?”

If syntax looks offensive, it is a sign simplification is needed – that’s the Ansible way, basically.

A simple shell call to check if the particular directory is in the output of “mount” would be cleaner.

- shell: blarg  
register: result

- shell: baz  
when: foo in result.stdout

OR

- shell: baz  
when: foo.rc != 2

ETC

would be preferable.

Alternatively, you could also write a custom facts module that returned the mounts

- action: my\_mount\_facts
- shell: baz  
when: ‘foo’ in mounts

etc

Things like that.