Nested containers

• what are nested containers?
• Nested containers Examples
• Nested Container indexing
• Nested Container Iteration

what are nested containers?

• Containers that have containers as items
• each level of nesting indicates the depth of the containers
• Matryoshka dolls

Nested list Examples

• collection of test scores (list of lists)

[[55,,60,93,28], [77,45,23,95],[23,88,62]]

• list of 3D coordinates (list of tuples)

[(1,1,1), (10,20,10),(-10,-10,-10),(20,0,0)]

• list of employee records (list of dictionaries)

[{'name':'James", 'hire_date':'2017/10/5'}, 
{'name':'Jana", 'hire_date':'2021/10/5'}, 
{'name':'Jae", 'hire_date':'2016/10/5'}, 
]

• Grocery Categories (dictionary of lists)

{
    'dairy':['milk', 'cheese','yoghurt'],
    'fruit':['apple', 'banana','grapes','durian'],
    'vegetable':['carrot', 'kale','lettuce','eggplant']
}

the keys are the categories, and the values are lists of items

• state information (dictionary of dictionaries)

{
    'CA':{'name': 'California', 'capital': 'Sacramento','area':'163696'},
    'OR':{'name': 'Oregon', 'capital': 'Salem','grapes','area':'93381'},
    'WA':{'name': 'Washington', 'capital': 'Olympia','area':'71362'}
}

Nested Container indexing

• Access parts of a nested container

• Consists of a series of index operators(a,b,c)

• the left most index represent the shallowest levels
• while the rightmost indexes represent the deepest levels. variable = [[[..]]] variable [a][b][c]

coord = [(-2,1),(2,-1),(3,4)]

	0	1	2
(-2,1)	(2,-1)	(3,4)

	expression	value
at coord[0]	we get the tuple (-2,1)

	expression	value
at coord[0]	we get the tuple (-2,1)

	expression	value
at coord[0][0]	-2
at coord[0][1]	1
at coord[1][0]	2
at coord[1][1]	-1

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Nested Container Iteration

• with nested containers, accessing every element requires nested iteration
• an iteration for every level of nesting
• each item is handed of the next level for further iteration

scorelist = [[38,62,93], [28], [64,76]]
#a list of lists
for outer_item in scorelist:
    #the outerloop
    for inner_item in outer_item:
        #inner loop
        print(inner_item, end='')
    print()

# Output

first iteration of the outer loop

	name	value
outer_item	[38,62,93]
inner_item	38

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