2D Dictionaries

   

2D Dictionaries 

Remember that dictionaries are very similar to lists, except that they store data as key:value pairs. The value is what it's worth and the key is what it is called. The key is used to access the value, and keys are more meaningful than index numbers.

Today we are going to expand our mad dictionary skills into the second dimension. 

Dynamically Adding To A 2D Dictionary 

This code dynamically adds to a 2D dictionary by starting with an empty dictionary and using an infinite loop to add user input.

EXAPMLE:

clue = {}

while True:

  name = input("Name: ")

  location = input("Location: ")

  weapon = input("Weapon: ")

  clue[name] = {"location": location, "weapon":weapon}#line 7

  print(clue)

The real magic happens on the 7th line of code. Instead of using .append() like we would with a list, we create a new dictionary entry.

The key is the name of the beast, but the value is a whole new dictionary that contains the details of the beast.
Each key:value pair in the dictionary is now a key that accesses a related dictionary.

Pretty Printing

This example shows you how to add a prettyPrint() subroutine that works with a 2D dictionary. 
 
def prettyPrint():
  print()
  
  for key, value in clue.items():
    # moves along every 'key:subDictionary' pair and outputs the key (the name of the character).
    print(key, end=": ")
    for subKey, subValue in value.items():
      # (nested) `for` loop moves along every subkey and subvalue in each subDictionary.
      print(subKey, subValue, end=" | ")
    print() 

Accessing a Single Item 

To access a single item in a 2D dictionary, we use two square brackets just like with a 2D list. 

his example stores users' data about their 100 Days Of Code progress. Note how I've set each one up as a 1D dictionary before storing them all in a 2D dictionary. 

john = {"daysCompleted": 46, "streak": 22}
janet = {"daysCompleted": 21, "streak": 21}
erica = {"daysCompleted": 75, "streak": 6}
courseProgress = {"John":john, "Janet":janet, "Erica":erica}
print(courseProgress) 

To access one item, I use two square brackets []. So to see only Erica's results, I would add:

print(courseProgress["Erica"])
# The bracket contains the key that references the sub dictionary.

👉 What if we only want to see how many days Erica has completed?

john = {"daysCompleted": 46, "streak": 22}
janet = {"daysCompleted": 21, "streak": 21}
erica = {"daysCompleted": 75, "streak": 6}
courseProgress = {"John":john, "Janet":janet, "Erica":erica}
print(courseProgress["Erica"]["daysCompleted"])
# The first bracket contains the key that references the sub dictionary. The second bracket contains the key that references the sub item. This will output '75'.