Two variable dictionary comprehension

Deborah Swanson python at
Tue Apr 4 01:18:22 EDT 2017

Thank you Nate, for all these sources to study. Python was very easy for
me to learn in 2 online courses, but it's been all uphill since then.
I've learned a lot and for that I'm grateful, but there's so much
farther to go.

I've appreciated our discussions, but I am in fact a very sick person
and my illness has come back again tonight. I can probably reply to a
few more posts and then you won't see me again for awhile.

But many thanks again, and I will begin reading the material you


Nathan Ernst wrote, on Monday, April 03, 2017 3:37 PM

No worries, Deborah.

Python is by most measurements a relatively easy/simple language to
learn, but there are always the dusty corners. If you've not already, I
recommend going through the online Python tutorial in it's entirety

After that, learn the language syntax that wasn't covered in the
tutorial by reading the Language Reference
( The tutorial should be
fairly easy for a straight beginner to follow. The language reference
assumes a little higher-level understanding of programming language
grammar.  The Python Language Reference uses a modified BNF syntax (BNF
being Backus-Naur form. You can read about BNF at To be honest,
I'm not sure what modifications Python uses to BNF, maybe someone else
can shed some light (or skin) on it.

After you'd done those, peruse the standard library. I don't recommend
deep reading there at this point, but at least a cursory reading so
you're cognizant of libraries that are built-in that may help do things
may you want to do now, or in the future (i.e. make a web request, parse
JSON or XML, handle datetimes).

Remember: Python comes with batteries included.


On Mon, Apr 3, 2017 at 5:09 PM, Deborah Swanson
<python at> wrote:

Nathan Ernst wrote, on April 03, 2017 1:59 PM
> I was a bit surprised when I looked at the language reference
> for 3.6.x. I expected there'd be a direct link to
> comprehensions, but there's not.
> You have to know what you're looking for:
> 6.2.5: List Displays
> 6.2.6: Set Displays
> 6.2.7: Dictionary Displays
> And, then, click on the appropriate element of the sub
> grammar to find the appropriate syntax.
> So, it took me about 30 seconds to find the appropriate
> grammars, when I expected it'd only take about 5 seconds,
> since I'm very familiar with the python docs & how the
> grammar documentation is laid out.  I can fully understand
> how someone less familiar with the documentation might have a
> harder time finding the grammar than I did.
> FWIW, If one was completely new to Python, even knowing the
> syntax is known as a "comprehension" might be unknown. I
> certainly didn't know what a comprehension was when I was
> learning Python. A coworker showed me, some 13 years ago.
> Regards,
> Nate

Thanks Nate, for your comprehension of the plight of many, if not most,
newish Python coders. And it certainly doesn't help to ask the list to
fill in some of the holes and be met with criticism for asking, but I
digress. It is what it is.

Before I started reading the list a few months ago, I'd heard of list
comprehensions in an article I'd read, and hardly understood the gist of
it. But look at me now Ma, I've learned not only how to use list
comprehensions but also a small tribe of other kinds of comprehensions!

(If there's a moral to this story, heck if I know exactly what it is.
"Keep on trying" is as good as any.)


> On Mon, Apr 3, 2017 at 3:47 PM, Jerry Hill
> <malaclypse2 at> wrote:
> > On Mon, Apr 3, 2017 at 10:30 AM, Deborah Swanson
> > <python at> wrote:
> > > Regular updates as the docs are updated would be a good idea too.
> > > It's obvious that today's Google isn't up to it, although
> it occurs
> > > to me that I haven't tried Google's site search on
> >
> > So, when you search google for the phrase "dict comprehension" or
> > "dictionary comprehension", nothing useful comes up for
> you?  When I
> > search either of those phrases, I get lots of useful
> results, all of
> > which spell out how to do what you were originally asking about.  I
> > know Google search results are skewed by past usage, but
> I'm surprised
> > that you didn't find anything useful in the first couple of search
> > results.
> >
> > When I do a search for 'dict comprehension' I get a boxed result
> > linking to PEP 274 as the first hit, then two Stack Overflow
> > questions, both of which demonstrate how to do dictionary
> > comprehensions.  Following that is another link to PEP 274,
> a link to
> > the Python docs on data structures (which does talk about dict
> > comprehensions, but it's way down on the page), and then links to a
> > bunch of tutorials.  If you had to judge based on my search
> results,
> > Google does a fine job of answering python questions, at least when
> > you already know the key phrase to look for.
> >
> > --
> > Jerry
> > --
> >
> >

> --

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