[TriZPUG] Tab completion in python shell

[Chris Calloway]

On 4/8/2015 9:12 AM, Luke Campagnola wrote:
> On Wed, Apr 8, 2015 at 9:14 AM, Chris Calloway <cbc at unc.edu
> <mailto:cbc at unc.edu>> wrote:
>     ipython is worth it.
>
> Can you expand on that? I haven't used it much but I presume it provides
> a lot more than history and tab completion.

Gladly, a little (no good deed goes unpunished, right?). There are 
hundreds of features, which I assume is what makes it intimidating for 
most. But you can just start using it in place of the vanilla 
interpreter prompt and learn as you go instead of trying to learn it all 
at once. Most of it you will never need anyway.

Out of those hundreds of features, I'd say my favorite is ??, which when 
placed after an identifier will take you directly to the source code for 
the referenced object. I've learned so much about the internals of 
standard library objects because of that.

I think the most popular feature is !, the system escape command. Being 
able to issue OS commands in the same shell easily is a no-brainer win. 
There are, of course, predefined aliases for things like cd, pwd, etc.. 
It keeps a directory history that makes it easy to navigate as well as 
supporting directory bookmarks. Also, anything in ipython that keeps a 
history is exportable.

I would probably use system command aliases more if I had a job where I 
did things repetitively every day.

I find persistent command history across sessions useful when it's not 
annoying. You can turn it off or clear it, of course.

Logging input to save sessions is indispensable in a job like mine where 
I spend a lot of time stumbling into broken code written by other people 
and I just want to create a Gist to reference in a Github issue that 
demonstrates the problem. (Hey, you earn green dots on GitHub for filing 
issues, you know, in case you're a streaker.)

Some features like auto-paren and auto-quote I find silly and don't use.

Cell mode (%%) is like having an Ipython Notebook cell in your 
interpreter prompt. There is also a magic command to export your session 
to an IPython Notebook.

Bash, Perl, and PowerShell cells.

Direct Github Gist pastebin support.

Inspect support. Get call signatures on demand quickly.

Pretty printing by default.

Profiler support.

SEARCHING FOR OBJECTS IN A NAMESPACE BY NAME AND/OR TYPE!

Special note to people working with GUI toolkits: GUI event loop 
integrations for wx, qt4/qt, gtk3/gtk, tk, and Cocoa.

Load numpy and matplotlib in pylab mode. (Actually I find pylab mode 
annoying as it encourages non-OO Matlab style programming which simply 
has to be unlearned in order to use matplotlib fully. But it is a quick 
and dirty path to a plot and low hanging fruit for the legions of Matlab 
drones.)

Clear a namespace of interactively defined crap.

Print all interactively defined crap in a namespace.

Namespace dump and load. I have used this on occasion.

If the bazillion things built into ipython aren't enough, there are 
bazillions of interactively loadable ipython extensions people have 
written. It makes more sense to find or write an ipython extension than 
it does to use an ipython alternative like bpython, because ipython is 
supported by the NumFocus Foundation and it going to be maintained for 
virtual forever.

There are lots of commands and extensions specifically just for IPython 
Notebooks, like making matplotlib plot inline into your notebooks or 
turning notebooks into reveal.js presentation. Extension culture is hard 
to keep up with as people are always coming up with more new cool things 
than there is time to investigate.

To get started, just fire up ipython. It immediately prints out a few 
commands to get help as soon as it starts. ? gives some very brief 
starter pointers. %quickref lists out a lot of commands in brief. %magic 
prints out a ton of information.

The most annoying thing about ipython is, "Do you really want to exit 
([y]/n)?" Of course, you can turn that off with --no-confirm-exit on the 
command line or in your .ipython file. But even having to look that up 
was annoying. Unnecessary configuration is alway annoying. Things should 
just work right out of the box.

-- 
Sincerely,

Chris Calloway, Applications Analyst
UNC Renaissance Computing Institute
100 Europa Drive, Suite 540, Chapel Hill, NC 27517
(919) 599-3530