python check if a number is in a certain position in nested list

Question

testlist = [[1, 2, 3, 0, 0], [0, 0, 3, 2, 1], [1, 0, 0, 3, 2], [2,3,1,0,0], [3,0,1,2,0], [2,0,1,3,0]]

I would like to check if the number 1 is in the third column of all the nested lists, if it is than it should replace the 1 with a 0 and the 2 in that list with a 1.

Thanks in advance

So, what have you tried to solve this problem? Also, don't use `list` to name a list. — cs95, Oct 29 '17 at 08:01
What is stopping you from reading the documentation and learning? — cs95, Oct 29 '17 at 08:10

Parth Verma · Answer 1 · 2017-10-29T11:38:55.197

1

You can try this:

testlist = [[1, 2, 3, 0, 0], [0, 0, 3, 2, 1], [1, 0, 0, 3, 2], [2,3,1,0,0],[3,0,1,2,0], [2,0,1,3,0]]
for ind,ele in enumerate(testlist):
    if ele[2] == 1:
        testlist[ind] = [i-1 if i in [1,2] else i for i in ele]

This should give you the output as follows

Input: testlist = [[1, 2, 3, 0, 0],
                   [0, 0, 3, 2, 1],
                   [1, 0, 0, 3, 2],
                   [2, 3, 1, 0, 0],
                   [3, 0, 1, 2, 0],
                   [2, 0, 1, 3, 0]]
Output: testlist -> [[1, 2, 3, 0, 0],
                     [0, 0, 3, 2, 1],
                     [1, 0, 0, 3, 2],
                     [1, 3, 0, 0, 0],
                     [3, 0, 0, 1, 0],
                     [1, 0, 0, 3, 0]]

edited Oct 29 '17 at 11:38

answered Oct 29 '17 at 08:39

Parth Verma

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Do I have to import anything – JoeJunior Oct 29 '17 at 08:41
No, everything used here is from the standard libraries and python built-ins – Parth Verma Oct 29 '17 at 08:43
@Parth Verma It replaces the 1 with a zero but not the 2 with a 1. – JoeJunior Oct 29 '17 at 08:58
@JoeJunior I thought that you wanted only that one replaced. Must have made that clear in the question – Parth Verma Oct 29 '17 at 11:37
"and the 2 in that list with a 1" Could you update your response please? – JoeJunior Oct 29 '17 at 11:49
@JoeJunior It is doing that – Parth Verma Oct 29 '17 at 12:29

score -1 · Accepted Answer · answered Oct 29 '17 at 08:45

For this, consider the testlist to be a matrix. You can solve this by using two for loops to loop each row and column.

testlist = [[1, 2, 3, 0, 0], [0, 0, 3, 2, 1], [1, 0, 0, 3, 2], [2,3,1,0,0], [3,0,1,2,0], [2,0,1,3,0]]

#traversing each row
for i, row in enumerate(testlist):
#traversing each column
   for j, c in enumerate(row):
   #in each column in the row check for '1', if found replace by '0'
      if j == 2 and c== 1:
         row[j] = 0
         #in the same row check for '2', if found replace my 1
         if 2 in row:
            ind = row.index(2)
            row[ind] = 1
print (testlist)

python check if a number is in a certain position in nested list

2 Answers2