Returning for loop inside a while loop in python

Question

I'm trying to make a function that returns this:

From this:

polje = [[1, 2, 4, 4], [4, 1, 4, 2], [2, 1, 4, 3], [2, 4, 2, 3], [1, 2, 3, 4]]

The function just goes through the lists and prints their elements starting with the last ones. I've been able to get the right result by printing, but i'm trying to make it so that the function simply returns the result. How do i do it? I've tried generators, single line for loops etc. but notes on the internet are not plentiful and are often writen in a complicated way...

Here's the code i've got so far:

def izpisi(polje):
    i = len(polje[0]) - 1
    while i >= 0:
        for e in polje:
            print(e[i], end="")
        i -= 1
        print("\n")
    return 0

Instead of printing, try saving the values in one element. Then add that element into an array/list. — RvdK
– RvdK, Commented Dec 27, 2014 at 9:56
Yea, i guess. I just need the function to return the proper values instead of printing them — x4nga
– x4nga, Commented Dec 27, 2014 at 10:15

jamylak · Accepted Answer · 2014-12-27 10:06:05Z

2

>>> polje = [[1, 2, 4, 4], [4, 1, 4, 2], [2, 1, 4, 3], [2, 4, 2, 3], [1, 2, 3, 4]]
>>> def izpisi(polje):
        return zip(*map(reversed, polje))

>>> for line in izpisi(polje):
        print(*line, sep='')


42334
44423
21142
14221

zip(*x) transposes a matrix. However you start at the last column so I simply add map(reversed,) to handle that.

The rest is just printing each line.

edited Dec 27, 2014 at 10:06

answered Dec 27, 2014 at 9:59

jamylak

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3 Comments

jamylak Over a year ago

You're using python2, i targeted this code at OP who is using Py3. First do from __future__ import print_function

x4nga Over a year ago

The problem is that this is still printing... I need it to work in a way that if i do print(izpisi(polje)), it will return 42334 44423 21142 14221

jamylak Over a year ago

Here you go: return '\n'.join(''.join(map(str, x)) for x in zip(*map(reversed, polje))). Note that it's much better to print line by line then keep a potentially big string in memory

Udy · Accepted Answer · 2014-12-27 10:03:31Z

1

you can change your code to store the items in a list instead of print them. and store each list in another list in order to return all of them.

like this:

def izpisi(polje):
    a = []
    i = len(polje[0]) - 1
    while i >= 0:
        l = []
        for e in polje:
            l.append(e[i])
        i -= 1
        a.append(l)
    return a

answered Dec 27, 2014 at 10:03

Udy

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Comments

Fomalhaut · Accepted Answer · 2014-12-27 15:25:52Z

0

def izpisi(polje):
    return '\n'.join([ # inserts '\n' between the lines
        ''.join(map(str, sublst)) # converts list to string of numbers
        for sublst in zip(*polje) # zip(*...) transposes your matrix
    ][::-1]) # [::-1] reverses the list

polje = [[1, 2, 4, 4], [4, 1, 4, 2], [2, 1, 4, 3], [2, 4, 2, 3], [1, 2, 3, 4]]
print izpisi(polje)

edited Dec 27, 2014 at 15:25

answered Dec 27, 2014 at 15:17

Fomalhaut

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