Tuples

Dictionary Items

items can be used to get keys and values from a dictionary

Example

runtimes = {
    "The Fellowship of the Ring": 178,
    "The Two Towers": 179,
    "The Return of the King": 201,
}

for kv_tuple in runtimes.items():
    print(kv_tuple)

Destructuring and for

Destructuring can be used to assign multiple variables in a for loop

runtimes = {
    "The Fellowship of the Ring": 178,
    "The Two Towers": 179,
    "The Return of the King": 201,
}

for movie, runtime in runtimes.items():
    print(f"{movie} is {runtime} minutes")

enumerate

enumerate can be used to add a count to iterable items
The return value from enumerate is an iterable of (count, value) tuples

Example

alphabet = "abcdefghijklmnopqrstuvwxyz"

print(list(enumerate(alphabet)))

Enumeration Loops

Enumeration can be used to avoid manual loops counters in certain loops

Example

alphabet = "abcdefghijklmnopqrstuvwxyz"

for letter in enumerate(alphabet):
    print(letter)

Exercise

Use enumerate to print only the letters with an even-numbered index in a string.

Modifying Lists Items

Enumeration can be helpful if we need a reference to list items during iteration

Example

nums = [1, 2, 3, 4, 5, 6, 7, 8]

for i, num in enumerate(nums):
    # Multiply every other value by 10
    if i % 2 == 0:
        nums[i] *= 10

print(nums)

Iterating multiple lists

It can be helpful to iterate multiple lists at the same time
This can be accomplished with an index

Example

names = ["Jordan", "Pam", "John"]
ages = ["19", "24", "23"]

for i, name in enumerate(names):
    age = ages[i]

    print(f"{name} is {age}")

zip

zip can be used to directly match items from two iterables
A new iterable is created providing tuples of items from the supplied iterators

Example

names = ["Jordan", "Pam", "John"]
ages = ["19", "24", "23"]

for pair in zip(names, ages):
    print(pair)

Example

names = ["Jordan", "Pam", "John"]
ages = ["19", "24", "23"]

for name, age in zip(names, ages):
     print(f"{name} is {age}")

Exercise

Use zip to create a list of each pair of letters in a string. For example, the string “abcd” should produce the following list:

[('a', 'b'), ('b', 'c'), ('c', 'd')]

Example

Score of a string