Why Dictionaries?
Dictionaries allow for elegant and intuitive code writing.
You might remember the Grocery List exercise from Ch. 6 Lists. In that exercise, you needed to make several lists to store quantities that were related to each other, such as the name of a grocery item, its price, and its quantity. You can use a single dictionary to do this instead of using multiple lists. It also makes more sense to use a dictionary for this because it explicitly associates the grocery item with its price and quantity.
Similarly, you can make a contacts list with a dictionary to map a person's name to their address.
# dictionaries as an alternative to parallel lists names = [ "Jane Doe", "John Williams", "Alex Summers" ] addresses = ["1234 Main St", "5678 Market Pl", "1357 Wall St"] # better solution: make a dictionary to # explicitly associate a name with an address # this is also called mapping a key to a value contacts = { "Jane Doe": "1234 Main St", "John Williams": "5678 Market Pl", "Alex Summers": "1357 Wall St" }
Another example is with using if-else blocks. A couple lines of if statements can get compressed into two lines. You are essentially spitting out multiple different outputs for multiple different inputs.
Implementation 1 using if statements
# implementation 1 using if statements value = 10 if value == 10: print("Tom") elif value == 20: print("Daniel") elif value == 30: print("Elizabeth")
Implementation 2 using dictionary
# implementation 2 using dictionary dict1 = {10: "Tom", 20: "Daniel", 30: "Elizabeth"} print(dict1[value])
Finally, dictionaries are much more flexible than lists because you aren't limited to using ordered indices to access, update, or retrieve elements.
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