# test-module fails during arg parsing with "zero length field name in format"

**URL:** <https://forum.ansible.com/t/test-module-fails-during-arg-parsing-with-zero-length-field-name-in-format/19786>\
**Category:** Ansible Project\
**Created:** [November 17, 2015, 5:47pm UTC](https://forum.ansible.com/t/test-module-fails-during-arg-parsing-with-zero-length-field-name-in-format/19786 "2015-11-17T17:47:15Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Larry\_Fast](https://avatars.discourse-cdn.com/v4/letter/l/b3f665/32.png) [@Larry\_Fast](https://forum.ansible.com/u/Larry_Fast)\
**Post date:** [November 17, 2015, 5:47pm UTC](https://forum.ansible.com/t/test-module-fails-during-arg-parsing-with-zero-length-field-name-in-format/19786/1 "2015-11-17T17:47:15Z")

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I’m just starting to develop my first module and test-module gives me an error during arg parsing. So I tried running test-module against ping.py and got the same error. See below. My first guess is it’s a python 2.6.6 problem. Any other ideas?

> ansible/hacking/test-module -m ansible/lib/ansible/modules/core/system/ping.py

Traceback (most recent call last):  
File “ansible/hacking/test-module”, line 207, in   
main()  
File “ansible/hacking/test-module”, line 189, in main  
options, args = parse()  
File “ansible/hacking/test-module”, line 67, in parse  
default=‘python={}’.format(sys.executable))  
ValueError: zero length field name in format

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<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:** [November 17, 2015, 9:03pm UTC](https://forum.ansible.com/t/test-module-fails-during-arg-parsing-with-zero-length-field-name-in-format/19786/2 "2015-11-17T21:03:25Z")

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It is a 2.6 issue. Put a 0 in the {}

Such as:

default=‘python={0}’.format(sys.executable))