Weird dictionary creation

Question

Could someone explain how the code attached works exactly. It is very non-intuitive for me.

https://code.sololearn.com/csURQIhxJhq2/?ref=app

Answer 1

You are using x[n] as temporary variable for loop. But x is global dictionary already so it retaining assigned values. ::( x[n] = next(arr) )
Generally temp variables gets deallocated automatically after loop.

Answer 2

Looks like a very dirty python hack 😱

I would never use this monstrosity in a real program...

Answer 3

https://code.sololearn.com/cXQvoIypK24x/?ref=app

Answer 4

Tibor Santa , Python still surprises me with the discovery of such things

https://code.sololearn.com/ccnFJx595Csn/?ref=app

Answer 5

Bob_Li ,

(a := [1,2,3]) and (x := {}) or [... for n, x[n] in enumerate(a, 1)] and print(x)

Answer 6

I think it just creates a key value pair based on the value of n, and then the value is the corresponding element in arr

Answer 7

I just don’t get what the use is. Do people actually develop software with these constructs?

Answer 8

😎 First time I've seen this trick.
It's hard to condense into a one-liner, though. I can't do it.
Anyone have a solution?

arr= ["a", "b", "c", "d"]

### turn this part to a one-liner ###
x={}
n=1
for x[n] in arr:
n+=1
##########################

print(x)

Answer 9

Vitaly Sokol
I know about the enumerate dictionary comprehension

a = ['a', 'b', 'c']
x = {i+1:v for i, v in enumerate(a)}
print(x)

but Edward Finkelstein's method did not use enumerate. I was wondering if there was a dictionary comprehension for that.

Answer 10

This works.
I wonder if use of range can be omitted?

a = ['a', 'b', 'c']
x ={i+1:a[i] for i in range(len(a))}
print(x)

Answer 11

Ok, use index(). I think this is as short as I can get it.

a = ['a', 'b', 'c']
x ={a.index(v)+1:v for v in a}
print(x)