[Tutor] Python functions are first-class citizens

[memilanuk]

On 07/31/2014 08:22 PM, Ben Finney wrote:
> memilanuk <memilanuk at gmail.com> writes:
 >> So... the similarity between dict.get() and dict.get as used here is
 >> kinda confusing me.
 >
 > I hope that helps. They are the same function; but the former is
 > *calling* the function object, and optionally using the return value;
 > the latter is referring to the function object *as* a value.

Conceptually, that makes sense.  Practically... having a little trouble 
getting my head around it - see below.


>> max_key = max(counts, key=counts.get)
>
> This specifies ‘counts.get’, without calling it. The expression
> ‘counts.get’ evaluates to that function object.
>
> That value is then used as the value for the ‘key’ parameter when
> calling ‘max’ here.

Been reading a bit more in the mean time, trying to grok that 'key' 
parameter for max()... and of course the python docs for max(iterable, 
key=) refer to the docs for list.sort() ;)

Kind of diverging off the original question a bit... but since it did 
include the max() code in it... I'm having a bit of difficulty with the 
whole 'key=' parameter when combined with counts.get here.

So counts is the iterable, and counts.get is the key used to iterate 
through it?

I guess I'm not getting how the whole key, function object bit works 
here in actual practice.

if we have

counts = {'a':1, 'b':22, 'c':100}

then counts.get('b') should return 22.  I got that much.

And counts.get is just an uncalled version of that:

foo = counts.get
foo('b')

should return 22 as well.  Think I got that as well.

Where things are going pear-shaped is how counts.get can function as a 
'key' when we don't actually supply () (or anything inside them) to 
specify what k,v pair we want, and how that relates back to the iterable 
for max(), counts?

Monte


-- 
Shiny!  Let's be bad guys.

Reach me @ memilanuk (at) gmail dot com