Today the question came up how to verify YAML files easily. Of course, there are many very good online parser. But I was wondering if it is possible to do it simply in Bash/ZSH, using a Python one-liner. Here is the code:
$ python -c 'import yaml,sys;yaml.safe_load(sys.stdin)' < yamltest.txt
It throws an exception if the file is not a proper (aka importable) YAML file. Otherwise it just returns with a 0 exit code.
Please note that I am not sure how tolerant yaml.safe_load is. And note that PyYAML needs to be installed.
Update:
Updated to avoid cat abuse – safe the kittens! Thanks to ichor!
/home/liquidat 
Please stop the cat abuse! ☺
python -c ‘import yaml,sys;yaml.safe_load(sys.stdin)’ < yamltest.txt
Argh, of course, sorry. Thanks very much for pointing out, I updated the post =)