# Multi-dimensional lists in Python

There can be more than one additional dimension to lists in Python. Keeping in mind that a list can hold other lists, that basic principle can be applied over and over. Multi-dimensional lists are the lists within lists. Usually, a dictionary will be the better choice rather than a multi-dimensional list in Python.

Accessing a multidimensional list:

Approach 1:

 `# Python program to demonstrate printing ` `# of complete multidimensional list ` `a ``=` `[[``2``, ``4``, ``6``, ``8``, ``10``], [``3``, ``6``, ``9``, ``12``, ``15``], [``4``, ``8``, ``12``, ``16``, ``20``]] ` `print``(a) `

Output:

```[[2, 4, 6, 8, 10], [3, 6, 9, 12, 15], [4, 8, 12, 16, 20]]
```

Approach 2: Accessing with the help of loop.

 `# Python program to demonstrate printing ` `# of complete multidimensional list row ` `# by row. ` `a ``=` `[[``2``, ``4``, ``6``, ``8``, ``10``], [``3``, ``6``, ``9``, ``12``, ``15``], [``4``, ``8``, ``12``, ``16``, ``20``]] ` `for` `record ``in` `a: ` `    ``print``(record) `

Output:

```[2, 4, 6, 8, 10]
[3, 6, 9, 12, 15]
[4, 8, 12, 16, 20]
```

Approach 3: Accessing using square brackets.
Example:

 `# Python program to demonstrate that we ` `# can access multidimensional list using ` `# square brackets ` `a ``=` `[ [``2``, ``4``, ``6``, ``8` `],  ` `    ``[ ``1``, ``3``, ``5``, ``7` `],  ` `    ``[ ``8``, ``6``, ``4``, ``2` `],  ` `    ``[ ``7``, ``5``, ``3``, ``1` `] ]  ` `         `  `for` `i ``in` `range``(``len``(a)) :  ` `    ``for` `j ``in` `range``(``len``(a[i])) :  ` `        ``print``(a[i][j], end``=``" "``) ` `    ``print``()     `

Output:

```2 4 6 8
1 3 5 7
8 6 4 2
7 5 3 1
```
Creating a multidimensional list with all zeros:

 `# Python program to create a m x n matrix ` `# with all 0s ` `m ``=` `4` `n ``=` `5` ` `  `a ``=` `[[``0` `for` `x ``in` `range``(n)] ``for` `x ``in` `range``(m)] ` `print``(a) `

Output:

```[[0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0], [0, 0, 0, 0, 0]]
```

Methods on Multidimensional lists

1. append(): Adds an element at the end of the list.
Example:

 `# Adding a sublist ` ` `  `a ``=` `[[``2``, ``4``, ``6``, ``8``, ``10``], [``3``, ``6``, ``9``, ``12``, ``15``], [``4``, ``8``, ``12``, ``16``, ``20``]] ` `a.append([``5``, ``10``, ``15``, ``20``, ``25``]) ` `print``(a) `

Output:

```[[2, 4, 6, 8, 10], [3, 6, 9, 12, 15], [4, 8, 12, 16, 20], [5, 10, 15, 20, 25]]
```

2. extend(): Add the elements of a list (or any iterable), to the end of the current list.

 `# Extending a sublist  ` ` `  `a ``=` `[[``2``, ``4``, ``6``, ``8``, ``10``], [``3``, ``6``, ``9``, ``12``, ``15``], [``4``, ``8``, ``12``, ``16``, ``20``]] ` `a[``0``].extend([``12``, ``14``, ``16``, ``18``]) ` `print``(a) `

Output:

```[[2, 4, 6, 8, 10, 12, 14, 16, 18], [3, 6, 9, 12, 15], [4, 8, 12, 16, 20]]
```

3. reverse(): Reverses the order of the list.

 `# Reversing a sublist  ` ` `  `a ``=` `[[``2``, ``4``, ``6``, ``8``, ``10``], [``3``, ``6``, ``9``, ``12``, ``15``], [``4``, ``8``, ``12``, ``16``, ``20``]] ` `a[``2``].reverse() ` `print``(a) `

Output:

```[[2, 4, 6, 8, 10], [3, 6, 9, 12, 15], [20, 16, 12, 8, 4]]
```

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