It took us a little while in class today to remember how 2D arrays work, so I thought I might go over it.
A 2 dimentional (2D) array is an array of arrays. So [[1,2,3,4],[5,6,7,8],[9,10,11,12]] is a 3 item array where each item is a 4 item array. This can be written as
[[1,2,3,4],
[5,6,7,8],
[9,10,11,12]]
You might notice that it looks like a grid (or matrix), this is where the 2D comes in to the name. In python we can create the array and assign it.
![2d](https://glow-prod-nl.s3.eu-west-1.amazonaws.com/nl/public/ColtnessHS-ComputingScience/uploads/sites/12638/2016/11/2D-300x212.png?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Security-Token=IQoJb3JpZ2luX2VjECUaCWV1LXdlc3QtMSJIMEYCIQC%2FXAI%2F1M5AhNddf72Ud5H7Aptc82ACPk81NeAWdDeQkAIhAJHDKcp%2FYOfRmT20a8Vwn1FHpJpxyM5lNCBk5y34uNTaKsEFCO7%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQBRoMMjczNTcwMTk1NDMzIgwimyCcu%2FMrNe%2Fhwl8qlQWFfvbj5ygPUEVf36MxPui%2Ft5sTXOUBt%2BcLf%2FKOlYQl7EriwhnP28ExR7owVgvGFxJybjvwuKdwjJpOZAN13nx7pfabZvyddoq%2BAT7%2F8gyr5YSVeL8q3Gzf65e1TAh8U5B%2FTrVr25n9XAgQ%2BepoP1zQ8jQDjMsD7grlelZJwTWH4XGoVQ%2F1m%2BhkgKLGwmjkGLvtbe%2FSb9G%2BI6M%2BiM22pVtwFP8SJbd%2BA19PUOSIffZGKT8sYoHJU4OPk0keiVmrt40hkkE5n8sg6hrNxyP%2FkIIphvnOeonyUbjchZGXn4zmaHRM9fhITzvyeO0WxDb5L7L%2BFfvrTYazS4WYrFjRLpMKbrsMs9JnET%2F%2Bzkfu7Me7zTc1PN2Fb9RPkbG5wQIWOW8k9lAILyrLJqK5twBrKv3SWZ%2B%2FrVd2gkkGQPfttX9Obid8MAMeJR%2Ftrqp19Ku6sNb3HzEr5Q2kXxzvs%2BOE%2BJtk6m3KUHFrLCMI5wowZIr%2Fl%2BVoh77kqfErF0Z0PmdOU5F87xW5BksNY2k2qXz08ia1U1JC0XoAM455Bxxog2xAaafKTb4Os4Odcq7bE5BrJ%2FmhBNVWUpacAcH2sRLQxGLmnS9u5ZeYQ%2BxMTEw1TPauz0LtAaY9rdlzlJrfuoMNXLJYUYoLurS6eYIH2zxQ9DGsB0nhDVyB8uIRkPDN2tQraYHR5710vdlPbi7b8b4OcP6Ft%2F1vLulBQhrpr0jKOyFsoZiabAoOCUi7EaySu7fpSPHdCeN9mbuSxN97a76Yd2bRwin3boYnk9RDUEchkcvUU6G0pojNRmZI5QFHWafh7dRIIve1OyqNwGnRSKoS7UDmHTPU3IwGTpiWHuAVSrom3yDDcKLYE2s6QwDxCxeHQmHcz9o%2BMOT13rQGOrABgi4fT%2Ba7E05uwn9ASTD35c2VnpmN5z0syTuB5%2FUCY90fXQ4oMVzM6oVH%2F3Nn3Hms7Vd8iZFIVPGGvOOo2WSlcwHfPY2HVallZfA8Ogn%2B3ODET89qOb8Lay6c49AMDFdqU3sRanph%2FLmQiLk1nkBwLG54boiECoqD0gQRZEtrJYU7bLdUW3SRQ4k%2FwJPWkBeA216HHiFUvCVE%2F4uAlLlc8vg17H7PlXkC94zSsD6kc18%3D&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=ASIAT7MQN47UYNGTFUOZ%2F20240717%2Feu-west-1%2Fs3%2Faws4_request&X-Amz-Date=20240717T132857Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Signature=be2e0d4a25de5ab3c4522f904468d102954cb92230fd255d4c1d1f7a1f81a6a7)
In the code above you can see the the individual elements of the 2D array are accessed using a pair of square brackets [][]. Using the image below we can see the [1][2] is number 7, as demonstrated in the program above.
We can use a loop to display each value in the 1st column.
![Using a for loop with a 2D array.](https://glow-prod-nl.s3.eu-west-1.amazonaws.com/nl/public/ColtnessHS-ComputingScience/uploads/sites/12638/2016/11/for2d-300x114.png?X-Amz-Content-Sha256=UNSIGNED-PAYLOAD&X-Amz-Security-Token=IQoJb3JpZ2luX2VjECUaCWV1LXdlc3QtMSJIMEYCIQC%2FXAI%2F1M5AhNddf72Ud5H7Aptc82ACPk81NeAWdDeQkAIhAJHDKcp%2FYOfRmT20a8Vwn1FHpJpxyM5lNCBk5y34uNTaKsEFCO7%2F%2F%2F%2F%2F%2F%2F%2F%2F%2FwEQBRoMMjczNTcwMTk1NDMzIgwimyCcu%2FMrNe%2Fhwl8qlQWFfvbj5ygPUEVf36MxPui%2Ft5sTXOUBt%2BcLf%2FKOlYQl7EriwhnP28ExR7owVgvGFxJybjvwuKdwjJpOZAN13nx7pfabZvyddoq%2BAT7%2F8gyr5YSVeL8q3Gzf65e1TAh8U5B%2FTrVr25n9XAgQ%2BepoP1zQ8jQDjMsD7grlelZJwTWH4XGoVQ%2F1m%2BhkgKLGwmjkGLvtbe%2FSb9G%2BI6M%2BiM22pVtwFP8SJbd%2BA19PUOSIffZGKT8sYoHJU4OPk0keiVmrt40hkkE5n8sg6hrNxyP%2FkIIphvnOeonyUbjchZGXn4zmaHRM9fhITzvyeO0WxDb5L7L%2BFfvrTYazS4WYrFjRLpMKbrsMs9JnET%2F%2Bzkfu7Me7zTc1PN2Fb9RPkbG5wQIWOW8k9lAILyrLJqK5twBrKv3SWZ%2B%2FrVd2gkkGQPfttX9Obid8MAMeJR%2Ftrqp19Ku6sNb3HzEr5Q2kXxzvs%2BOE%2BJtk6m3KUHFrLCMI5wowZIr%2Fl%2BVoh77kqfErF0Z0PmdOU5F87xW5BksNY2k2qXz08ia1U1JC0XoAM455Bxxog2xAaafKTb4Os4Odcq7bE5BrJ%2FmhBNVWUpacAcH2sRLQxGLmnS9u5ZeYQ%2BxMTEw1TPauz0LtAaY9rdlzlJrfuoMNXLJYUYoLurS6eYIH2zxQ9DGsB0nhDVyB8uIRkPDN2tQraYHR5710vdlPbi7b8b4OcP6Ft%2F1vLulBQhrpr0jKOyFsoZiabAoOCUi7EaySu7fpSPHdCeN9mbuSxN97a76Yd2bRwin3boYnk9RDUEchkcvUU6G0pojNRmZI5QFHWafh7dRIIve1OyqNwGnRSKoS7UDmHTPU3IwGTpiWHuAVSrom3yDDcKLYE2s6QwDxCxeHQmHcz9o%2BMOT13rQGOrABgi4fT%2Ba7E05uwn9ASTD35c2VnpmN5z0syTuB5%2FUCY90fXQ4oMVzM6oVH%2F3Nn3Hms7Vd8iZFIVPGGvOOo2WSlcwHfPY2HVallZfA8Ogn%2B3ODET89qOb8Lay6c49AMDFdqU3sRanph%2FLmQiLk1nkBwLG54boiECoqD0gQRZEtrJYU7bLdUW3SRQ4k%2FwJPWkBeA216HHiFUvCVE%2F4uAlLlc8vg17H7PlXkC94zSsD6kc18%3D&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=ASIAT7MQN47UYNGTFUOZ%2F20240717%2Feu-west-1%2Fs3%2Faws4_request&X-Amz-Date=20240717T132857Z&X-Amz-SignedHeaders=host&X-Amz-Expires=900&X-Amz-Signature=4954a715a52a189d6019cda17b6078cadbbb85682af19d81c51546e1d7c37852)
Or a nested for to display each item in each array