does puppy come with Python installed on it in order to install electrum?
and by the way for puppy you only need like half a gigabyte to put it and then you can even remove the USB and continue running it completely from the RAM
No, I don't think its equipped with python.
The electrum wallet is available from genuine, Puppy repository.
It will download and install all necessary dependences.
Java will be quite different story...
Yes, the system itself will use like 256MB of USBstick but it is recommended to use pen drives of around 2GB capacity, for personal & system data storage.
Running from RAM alone is actually great, but minimum 1024MB of RAM is required, for best stability.