Define a two-dimensional array in Python

# Define a two-dimensional array in Python

David Y.

How can I create an empty two-dimensional array in Python, e.g. for matrix operations?

## The Solution

The best way to create two-dimensional (2D) arrays or matrices is by using Python’s `numpy` module, which provides comprehensive and performant functionality for manipulating multidimensional arrays. We can create a 2D array by passing a tuple to the `zeros` function. The following code will create a 3-by-3 2D array with all values set to zero:

Click to Copy
```.css-3i4pd0{position:relative;color:inherit;-webkit-transition:box-shadow 0.3s;transition:box-shadow 0.3s;will-change:box-shadow;outline:0;display:-webkit-box;display:-webkit-flex;display:-ms-flexbox;display:flex;-webkit-flex-direction:column;-ms-flex-direction:column;flex-direction:column;z-index:9;}.css-3i4pd0:hover,.css-3i4pd0:focus{cursor:pointer;}.css-3i4pd0:hover .e1fliqfg1,.css-3i4pd0:focus .e1fliqfg1{fill:#e1567c;cursor:pointer;}import numpy

matrix = numpy.zeros((3,3))

# array([[0., 0., 0.],
#        [0., 0., 0.],
#        [0., 0., 0.]])
```

Note that `numpy.matrix` is deprecated and should not be used for this operation.

To create a 2D array without using `numpy`, we can initialize a list of lists using a list comprehension. This will be slower and deprive us of the use of `numpy`’s matrix operations, but may be desirable in cases where we don’t want to add the dependency. We can use code similar to the following:

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```matrix = [[0 for x in range(3)] for y in range(3)] # x = width, y = height
# [[0, 0, 0], [0, 0, 0], [0, 0, 0]]
```

In both of these structures, we can read and write individual elements with the following syntax:

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```matrix[0][0] = 1 # set top-left corner to 1

print(matrix[2][2]) # print value of bottom-right corner
```
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