Full disclosure - I'm a Puppet Labs employee.
I recommend that you learn Puppet and get familiar with the types of problems it solves. Python, while an interesting and useful language, is another type of scripting language. If you're already familiar with other scripting languages, my opinion is that learning it will not necessarily make you more valuable in the marketplace. Also, if I had to guess, there may be up to an order of magnitude more developers with Python experience than Puppet experience. My feeling is that it's better to be a big fish in a small pond, if you can.
As companies have to solve harder problems at the intra- and inter-datacenter level to stand up their business-critical infrastructure, they use Puppet to do so, not Python, Perl, Ruby or shell scripts. At least, they shouldn't do that, and that's what we're trying to help them stop doing!
I hope that information is helpful, and please post any follow-up questions you may have. Good luck!