just started

[metal.suomi at gmail.com]

> In theory, "pip3" will install into the default "python3", whichever
> that is. However, in practice, it's entirely possible that it installs
> into a very different Python from the one you're expecting. The most
> reliable form is the latter; whatever command you use to start Python,
> add "-m pip" to it, and you know you're talking to that same
> installation.

thanks! very clarifying. One more question though: after installing python3.5 I only have pip3 and pip3.5 from the command line. However, I issued the command 

python3.5 -m pip install matplotlib

and it all went like a charm. At the end of the install, it said "You are using pip version 8.1.1, however version 9.0.1 is available. You should consider upgrading via the 'pip install --upgrade pip' command"

However, the command 
pip install --upgrade pip' command
doesn't work. So, it seems like pip is not installed. which pip3.5 tells me
/Library/Frameworks/Python.framework/Versions/3.5/bin/pip3.5

so I'm confused. I have only pip3.5 and the command python3.5 -m pip install .... automatically translates into pip3.5 ?