What happens to a file during a commit to SVN?

Question

I had a task to check and test incoming commits of a .yaml config file to our svn repository. My test was very simple, I would load the file and if it returned a dict type then it was good to go.

My first thought was to use svnlook cat to print the file to stdout, store the contents in a python object and then load the object. This worked for me previously when reading directly from our repository. This method seemed to return a nonetype every time though, even when I knew the syntax of the file to be correct. (I was using a pre-commit variable $TXN)

I solved this by piping svnlook cat to a temporary .yaml file and running my test from there.

I'm wondering why the latter method works but the first does not. All I can think of is that during the commit transaction, the file is skewed somehow. Again, I am fairly new to this and am looking to understand where I went wrong so I can learn from this.

Apologies for any incorrect terminology and thanks for helping me better myself!