Python-Intermediate-Notes

Dictionary

Dictionary is a collection of unordered data, which is stored in key-value pairs.

price_list = {
    "jeans": 134,
    "shirt": 135, 
    "shoes": 153,
}

Key-Value pairs

A key-value pair is a set of values associated with each other.

price_list = {
    "jeans": 134, #key-value pair
    "shirt": 135, 
    "shoes": 153,
}

Key

Key is a unique identifier for some item in the data.

price_list = {
    "jeans": #Key
}

Value

The value is that data that is identified or a pointer to the location of the data.

price_list = {
    "jeans": 425 #value - 425
}

.update() method

The update method updates dictionary with the specifies key and value pairs.

price_list.update =  ({
    "boots": 563,
    "sneakers": 326 })

zip() function

The zip function is used to quickly combine associated data-sets without needing to rely on multi-dimensional lists.

var1 = ["weight", "height"]
var2 = [35, 536]
combined_variables = zip(var1, var2)

dict function

The dict function turns the combined list into a dictionary

relative = ["a", "b", "c"]
num = [1, 2, 3]
dictVar = dict(zip(relative, num))
print(dictVar)

Navigating in dictionary

Getting a key from the dictionary

test_scores = {"jonathan": 64, "abra": 98, "key": 86, "jane": 36}
print(test_scores["jane"])

KeyError occurs when you input a key that isn’t present in the dictionary/code

Checking if the key is present

check_Key = "andrew"

if check_Key in text_scores:
    print(check_Key, "took the test")
else:
    print(check_Key, "didn't took the test")

.get()method

The .get()method shows us the key we’re looking for. If it doesn’t exist, it return none.

print(test_scores.get("abra"))
print(test_scores.get("cong")) #print "None" if it doesn't exist

.pop()method

If you want to delete a key in the dictionary/code

neighbors = {"Ms. Santos": "fruitcake", "Toni": "socks", "Alex": "vinegar"}
neighbors_pop = neighbors.pop("Ms. Santos")
print(neighbors_pop)

.keys()method

If you want to get all the keys without their values

neighbors = {"Ms. Santos": "fruitcake", "Toni": "socks", "Alex": "vinegar"}
y = neighbors.keys()
print(y)

.values()method

To get all the values without their keys

neighbors = {"Ms. Santos": "fruitcake", "Toni": "socks", "Alex": "vinegar"}
done = neighbors.pop("Ms. Santos")
w = neighbors.values()
print(w)

.items()method

Shows both keys and values

neighbors = {"Ms. Santos": "fruitcake", "Toni": "socks", "Alex": "vinegar"}
done = neighbors.pop("Ms. Santos")
z = neighbors.items()
print(z)

Looping Through Dictionaries

neighbors = {"Ms. Santos": "fruitcake", "Toni": "socks", "Alex": "vinegar"}

using .items()

for key, value in neighbors.items():
    print(key)
    print(value)

using .keys()

for name in neighbors.keys():
    print(name)

continue

for name in neighbors.keys():
    if name == "Ms. Santos":
        continue
    print(name)

.values()

for gift in neighbors.values():
    print(gift)

nested keyword (dictionary within a dictionary)

cat = { 1: {"name": "pepper", "age": 5, "color": "black"}, 
        2: {"name": "sashimi", "age": 6, "color": "gray"} }

[] to access elements of each dictionaries

print(cat[2]["age"])
print(cat[1]["color"])

{} create a new dictionary

cat[3] = {}
cat[3]["name"] = "tuna"
cat[3]["age"] = 2
cat[3]["color"] = "orange"
cat[3]["personality"] = "wild"
print(cat[3])
print(cat[3]["personality"])
print(cat[1])

another method to add a dictionary

cat[4] = {"name": "sushi", "age": 10, "color": "white", "personality": "shy"}
print(cat[3])
print(cat[4])
print(cat[4]["age"])

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