Function programming in Python

Question

I'm trying to define a new function called new_f, just for practice:
The purpose of function is:

x = ['1', '2', '3', '4'] y = new_f(x) print(y)

And that should give:

['4', '3', '2', '1']

So it's a reverse of x.
I tried something like this:

def new_f(x): y = len(x) for z in range(y-1,-1,-1): r = print([x[z]]) return r

But that gives:

['4'] ['3'] ['2'] ['1']

Ok, that's not what I want, so maybe:

--------- for z in range(y-1,-1,-1): r = [x[z]] return r

And I get:

['1']

So he goes through all z and gives me the last one.
How can I resolve this problem?
Thanks in advance.

list[::-1] means you've masked the built-in function list() with a reference to an object of type list. — TigerhawkT3
– TigerhawkT3, Commented Apr 29, 2015 at 23:04

Kasravnd · Accepted Answer · 2015-04-29 23:14:16Z

You can initial r as an empty list and append the elements to it and at last return the r

def new_f(x): y = len(x) r=[] for z in range(y-1,-1,-1): r.append(x[z]) return r

But there are some elegant and more pythonic ways for reversing a list like reverse indexing :

the_list[::-1]

or built-in reversed function :

reversed(the_list)

hebrewduck · Accepted Answer · 2015-04-29 23:02:43Z

You can use Python's slicing operator to reverse a list.

def new_f(x): return x[::-1]

Alireza Bashiri · Accepted Answer · 2015-08-06 18:09:03Z

1

Maybe you'd find them useful:

def reverse_list(x): return x.reverse() def reverse_list(x): return x[::-1] def reverse_list(x): yield from reversed[x]

answered Apr 29, 2015 at 23:06

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2 Comments

Hey, I think instead of yield from reversed(x) you can just do return reversed(x). I mean it's the same exact thing, just shorter, and faster.

oh, yes. It's returns list_reverseiterator empty instance but yield returns a generator empty instance, that's the only difference :D