CODEWITHSUNDEEP
python
user3221453
user3221453

Reputation: 77

Inserting values in a list in a list

So i have

matrix = [['B Borg', '3', '3', '1.0'], ['F Perry', '7', '8', '0.875'], ['R Nadal', '3', '5', '0.6']]

I want to make it look like this:

[['1','B Borg', '3', '3', '1.0'], ['2','F Perry', '7', '8', '0.875'], ['3','R Nadal', '3', '5', '0.6']]

I've tried

matrix.insert([0][0],"1")
matrix.insert([1][0],"2")
matrix.insert([2][0],"3")

But the end result is:

matrix = ["1",",2","3"['B Borg', '3', '3', '1.0'], ['F Perry', '7', '8', '0.875'], ['R Nadal', '3', '5', '0.6']]

My guess is that i messed up the indexing in the insert part, but i just cannot figure out what i did wrong.

Upvotes: 2

Views: 84

Answers (4)

John La Rooy
John La Rooy

Reputation: 304167

If you loop over the matrix, the items will be the things you need to insert into

>>> matrix = [['B Borg', '3', '3', '1.0'], ['F Perry', '7', '8', '0.875'], ['R Nadal', '3', '5', '0.6']]
>>> for i, item in enumerate(matrix, 1):
...     item.insert(0, str(i))
... 
>>> matrix
[['1', 'B Borg', '3', '3', '1.0'], ['2', 'F Perry', '7', '8', '0.875'], ['3', 'R Nadal', '3', '5', '0.6']]

Upvotes: 0

inspectorG4dget
inspectorG4dget

Reputation: 113955

>>> matrix = [[str(i)]+subl for i,subl in enumerate(matrix, 1)]
>>> matrix
[['1', 'B Borg', '3', '3', '1.0'], ['2', 'F Perry', '7', '8', '0.875'], ['3', 'R Nadal', '3', '5', '0.6']]

Or, use the consume itertools recipe:

>>> matrix = [['B Borg', '3', '3', '1.0'], ['F Perry', '7', '8', '0.875'], ['R Nadal', '3', '5', '0.6']]
>>> collections.deque((subl.insert(0, str(i)) for i,subl in enumerate(matrix, 1)), maxlen=0)
deque([], maxlen=0)
>>> matrix
[['1', 'B Borg', '3', '3', '1.0'], ['2', 'F Perry', '7', '8', '0.875'], ['3', 'R Nadal', '3', '5', '0.6']]

Upvotes: 0

fivetentaylor
fivetentaylor

Reputation: 1287

Try this:

matrix2 = [[str(i+1)] + x for i,x in enumerate(matrix)]

Upvotes: 0

abarnert
abarnert

Reputation: 365717

The problem is that [0][0] is the first element in the list [0]—that is, 0. So, matrix.insert([0][0], "1") is the same as matrix.insert(0, "1"). In other words, it inserts a new row at the top of the matrix, with only a single value, "1".

What you want is matrix[0].insert(0, "1"). Since matrix[0] is the first row in the matrix, this inserts a new column at the left end of the first row.

Upvotes: 5

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