How to make each element in a list another list in python

Question

I have a list inside a loop for e.g

A=[25,45,34,....87]

in the next iteration A should be

A=[[25,32],[45,13],[34,65],....[87,54]]

in the next iteration A should be

A=[[25,32,44],[45,13,67],[34,65,89],....[87,54,42]]

and so on.How can i do that?is it possible?The code i am working on is

    s=0
    e=25
    for i in range(0,4800):
        if not m_list_l:
            m_list_l.append(max(gray_sum[s:e]))
        m_list_l[i].append(max(gray_sum[s:e]))
        s+=25
        e+=25

But this give me Error as

m_list_l[i].append(max(gray_sum[s:e]))
AttributeError: 'int' object has no attribute 'append'

What should m_list_l[i].append() do before there are nested lists? — Natecat
– Natecat, Commented Dec 16, 2016 at 5:58
@Natecat i declared m_list_l as an empty list in the beginning of the program — Emmanu
– Emmanu, Commented Dec 16, 2016 at 6:02
It's not clear where the extra elements are coming from and what gray_sum and m_list_l are. Can you update your question to include a runnable example that produces the error? — Noufal Ibrahim
– Noufal Ibrahim, Commented Dec 16, 2016 at 6:02

Natecat · Accepted Answer · 2016-12-16 06:07:44Z

1

The first element you insert should be a list, not an int. Change m_list_l.append(max(gray_sum[s:e])) to m_list_l.append([max(gray_sum[s:e])]) to fix this.

edited Dec 16, 2016 at 6:07

answered Dec 16, 2016 at 5:59

Natecat

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1 Comment

Emmanu Over a year ago

Thank you very much..Worked fine.I changed the declaration to 'm_list_l= [[x] for x in range(0,4800)]' and it worked.

Suresh2692 · Accepted Answer · 2016-12-16 06:11:15Z

0

Say there are two lists as

A = [i for i in range(10,100,10)]
A
[10, 20, 30, 40, 50, 60, 70, 80, 90]

B = [i for i in range(20,100,10)]
B
[20, 30, 40, 50, 60, 70, 80, 90, 100]

The combined list would be

L = [[i,j] for i,j in zip(A,B)]
L
 [[10, 20],
 [20, 30],
 [30, 40],
 [40, 50],
 [50, 60],
 [60, 70],
 [70, 80],
 [80, 90],
 [90, 100]]

answered Dec 16, 2016 at 6:11

Suresh2692

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1 Comment

Moinuddin Quadri Over a year ago

list(zip(A,B)) will do the same. You do not need list comprehension to achieve this

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