Storing the result of a for loop in a array

Question

I am trying to save the result of a nested for loop in a list in python. can someone tell me how to do it? V is an array containing [1, 2, 3] while n is the length = 3 and sq is the matrix containing swaps.

i have tried many approaches but whenever i return the result it only gives me one element of the list. any help would be appreciated. Thankyou

def Permute1(sq,v,n):
        for i in range(n):
            for j in range(n):
                if (sq[i,j]==1):
                    temp=v[i]
                    v[i]=v[j]
                    v[j]=temp
                    print(v)



results: 
[1, 2, 3]
[2, 1, 3]
[3, 1, 2]
[3, 1, 2]
[3, 2, 1]
[3, 2, 1]

declare an empty list before `for` loops and append the values — Sociopath, Jan 29 '19 at 10:57
i have tried doing it. but it turns out when i return the list it gives me only the last element in the list. i.e [3,2,1] — AAT, Jan 29 '19 at 10:59
`a=[] for i in range(n): for j in range(n): if (sq[i,j]==1): temp=v[i] v[i]=v[j] v[j]=temp a.append(v) print(a)` — AAT, Jan 29 '19 at 11:01
returns [[3, 2, 1], [3, 2, 1], [3, 2, 1], [3, 2, 1], [3, 2, 1], [3, 2, 1]] — AAT, Jan 29 '19 at 11:01
You need to append a **copy** of `v` to `a`. Python will never copy anything (except numerical values) implicitly. — meowgoesthedog, Jan 29 '19 at 11:01

score 0 · Accepted Answer · answered Jan 29 '19 at 11:02

0

I'm not sure what is the utility of d = vhere.

To swap two elements in Python, I recommend:

v[i], v[j] = v[j], v[i]

Declaring an empty list before for loops and append the values (like AkshayNevrekar said) can also be useful, depending on what you need as a result.

answered Jan 29 '19 at 11:02

DeusDev

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sorry it was a line added by mistake – AAT Jan 29 '19 at 11:04
Could you give the complete code with the parameters you are passing to the function? Just to see if I can get to your desired answer. – DeusDev Jan 29 '19 at 11:08

score 0 · Answer 2 · edited Jan 29 '19 at 11:34

0

Check yield. You can use this to generate all the permutations and process each one of them & store them in a list.

edited Jan 29 '19 at 11:34

Georgy

12,464
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answered Jan 29 '19 at 11:07

taurus05

2,491
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Mohit · Answer 3 · 2019-01-29T11:13:47.923

0

def Permute1(sq,v,n):
    result=[]
    for i in range(n):
        for j in range(n):
            if (sq[i,j]==1):
                temp=v[i]
                v[i]=v[j]
                v[j]=temp
                result += [v]
    print(result)
    return result

No tested but may be it can help.

edited Jan 29 '19 at 11:13

answered Jan 29 '19 at 11:08

Mohit

93
10

Storing the result of a for loop in a array

3 Answers3