I always have a program open that's called pcalc as well, but it's something homebrew and short for Python calculator. It's just a Python repl (enhanced by python-prompt-toolkit) with a bunch of my own pre-defined functions: https://github.com/orlp/dotfiles/blob/master/pcalc/pcalc

I use it all the time, it's so incredibly useful. My most used pre-defined functions are... copy(s) and paste(). E.g. doubling a comma-separated list of numbers is one simple

    copy(", ".join(x*2 for x in eval(paste())))

away.