Python Collections

Question 1

TF: Lists are mutable and strings are immutable:

Answer 1

True. When you change a list, it’s now different but it still takes up the same spot in the memory. A string however, when you change it, it takes up a new spot in memory.

Question 2

This challenge is just meant as a refresher. Create a single new list variable named my_list. Put 3 numbers and 2 strings into it in whatever order you want. For the last member, though, add another list with 2 items in it.

Answer 2

my_list = [1, 2, 3, “Jon”, “Snow”, [5, 6]]

Question 3

Create a list named best that has three items in it. The items can be anything you want.

Using .extend(), .append(), or +, add two new items onto the end of best. Again, the items can be anything you want.

Finally, use the .insert() method to place the string “start” at the beginning of your best list.

Answer 3

best = [1, 2, 3]

best. extend([4, 5])
best. insert(0, “start”)

Question 4

TF: The + symbol is used to concatenate two lists together, just like with strings.

Answer 4

True

Question 5

What does the first_list.extend(second_list) method do?

Answer 5

Adds the contents of a second list onto the first list

Question 6

letters = [“A”, “B”, “C”]
letters.append([“D”, “E”, “F”])
What will letters be at the end of this?

Answer 6

[“A”, “B”, “C”, [“D”, “E”, “F”]]

Question 7

I want my_list to have 1 as the last item.
Complete this method call:

My_list. _________ (1)

Answer 7

append

Question 8

What does the list() function do?

Answer 8

Creates a new list & turns an iterable into a list.

Question 9

What is the first argument to the .insert() method?

Answer 9

Index - the position in the list that you want something inserted

Question 10

What are the 2 ways we can delete an item from the list?

alpha_list = [“A”, “B”, “C”, “D”, “E”]

Answer 10

Del
del alpha_list[2]
.remove()
alpha_list.remove(“D”)

Question 11

If you use .remove, and there are multiple items in the list with the same name? What will happen? My_list = [1, 2, 3, 4, 1] my_list.remove(1)

Answer 11

It will remove the first 1 in the list and keep the second. So [2, 3, 4, 1]

Question 12

What happens if we try to .remove() an item that doesn’t exist in the list?

Answer 12

We get a ValueError

Question 13

What does ‘pass’ do?

Answer 13

A pass is essentially a “do nothing” statement.

Question 14

OK, I need you to finish writing a function for me. The function disemvowel takes a single word as a parameter and then returns that word at the end.
I need you to make it so, inside of the function, all of the vowels (“a”, “e”, “i”, “o”, and “u”) are removed from the word. Solve this however you want, it’s totally up to you!
Oh, be sure to look for both uppercase and lowercase vowels!

def disemvowel(word):
    return word

Answer 14

def disemvowel(word):
    new_word = ""
    vowels = ["a", "e", "i", "o", "u", "A", "E", "I", "O", "U"]
    for letters in word:
        if letters not in vowels:
            new_word += letters
    return new_word

Question 15

What does .pop do?

Answer 15

.pop() will remove and return the last item from a list.

names.pop()

Question 16

What do you have to use if you want to pop an item that isn’t the last one in the list?

Answer 16

.pop(index) will remove whatever index the item is at, assuming something is.
names.pop(0)

Question 17

Alright, my list is messy! Help me clean it up!
First, start by moving the 1 from index 3 to index 0. Try to do this in a single step by using both .pop()and .insert(). It’s OK if it takes you more than one step, though!

messy_list = ["a", 2, 3, 1, False, [1, 2, 3]]
# Your code goes below here

Great! Now use .remove() and/or del to remove the string, the boolean, and the list from inside of messy_list. When you’re done, messy_list should have only integers in it.

Answer 17

messy_list.pop(3)
messy_list.insert(0, 1)

messy_list.remove(“a”)
messy_list.remove(False)
messy_list.remove([1, 2, 3])

Question 18

What is a slice?

Answer 18

A slice is a new list or string made from another list or string.
If you make a slice from a list, you get a list.
If you make a slice from a string, you get a string.
[start:stop]
Favorite_things[1:4]

Question 19

What happens when you don’t provide a value for the start or end off of a slice?

Answer 19

Both start and stop are optional. If you leave off start, the slice will start at the beginning of the iterable. If you leave off stop, the slice will continue until the end of the iterable.

Question 20

Create a new variable named slice1 that has the second, third, and fourth items from favorite_things.

favorite_things = [‘raindrops on roses’, ‘whiskers on kittens’, ‘bright copper kettles’, ‘warm woolen mittens’, ‘bright paper packages tied up with string’, ‘cream colored ponies’, ‘crisp apple strudels’]

OK, let’s do another test. Get the last two items from favorite_things and put them into slice2.

Make a copy of favorite_things and name it sorted_things.
Then use .sort() to sort sorted_things.

Answer 20

slice1 = favorite_things[1:4]

slice2 = favorite_things[5:]

sorted_things = favorite_things[:]
sorted_things.sort()

Question 21

How do you splice with a step?

Answer 21

[start:stop:step]
Numbers[::2] → this will show us the entire list and skip every 2
Numbers[::-1] → this will give us the entire list, but backwards.

Question 22

In this first one, create a function named first_4 that returns the first four items from whatever iterable is given to it.

OK, this second one should be pretty similar to the first. Make a new function named first_and_last_4. It’ll accept a single iterable but, this time, it’ll return the first four and last four items as a single value.

OK, try this one on for size: create a new function named odds that returns every item with an odd index in a provided iterable. For example, it would return the items at index 1, 3, and so on.

Make a function named reverse_evens that accepts a single iterable as an argument. Return every item in the iterable with an even index…in reverse.
For example, with [1, 2, 3, 4, 5] as the input, the function would return [5, 3, 1].

Answer 22

def first_4(list):
    return list[0:4]

def first_and_last_4(list):
    return first_4(list) + list[-4::1]

def odds(list):
    return list[1::2]

def reverse_evens(list):
return list[::2][::-1]

Question 23

a_list = [1, 2, 3]
a_list _____
Copy the entire list with a slice.

Answer 23

a_list[:]

Question 24

[1:] will stop where?

Answer 24

The end of an iterable

Question 25

TF: Slices can only be used on lists.

Answer 25

False

Question 26

[:4] will start at what index?

Answer 26

0

Question 27

How do you delete using slices? Delete Black to Aqua

rainbow = [“red”, “orange”, “green”, “yellow”, “blue”, “black”, “white”, “aqua”, “puple”, “pink”]

Answer 27

del rainbow[5:8]

Question 28

How do you change the order of a list using slices?
Swap green and yellow
rainbow = [“red”, “orange”, “green”, “yellow”, “blue”, “black”, “white”, “aqua”, “puple”, “pink”]

Answer 28

rainbow[2:4] = [“yellow”, “green”]

Question 29

How would you add “indigo‘ after blue using slices?

Answer 29

rainbow[4:5] = [“blue”, “indigo”]

Question 30

TF: When replacing a slice with another iterable, they must be the same size.

Answer 30

False

Question 31

What step do I want to use if I want every item in reverse?

Answer 31

-1

Question 32

grades = [70, 82, 94, 105, “B”, “A”, 72, “D”]

Given the above list, how would I delete the letter grades?

Answer 32

del grades[4:6]

del grades[-1]

Question 33

Name the three parts of the slice syntax.

[_____ : ______ : ______]

Answer 33

Start, stop, step

Question 34

grades = [70, 82, 94, 105, “B”, “A”, 72, “D”]

Given the above list, how would I replace the middle two letter grades with 89 and 94?

Answer 34

Grades[4:6] = [89. 94]

Question 35

______ my_list[2:5]

What keyword do I need to use to remove this slice from the list?

Answer 35

Del

Question 36

This one will be named sillycase and it’ll take a single string as an argument.
sillycase should return the same string but the first half should be lowercased and the second half should be uppercased.
For example, with the string “Treehouse”, sillycase would return “treeHOUSE”.
Don’t worry about rounding your halves, but remember that indexes should be integers. You’ll want to use the int() function or integer division, //.

Answer 36

def sillycase(word):

return word[:len(word)//2].lower() + word[len(word)//2:].upper()

Question 37

What are dictionaries?

Answer 37

Data set that is like an unordered list of keys and values.

course = {“title”: “Python Collections”}

Question 38

What happens when you search for a value using a key in a dictionary that does not exist?

Answer 38

KeyError

Question 39

Make a dictionary named player and add two keys to it. The first key should be “name” and the value can be any string you want.
The second key should be “remaining_lives”. Set this key’s value to 3.

Now add a “levels” key. It should be a list with the values 1, 2, 3, and 4 in it.
And, lastly, add an “items” key. This key’s value should be another dictionary. Give it at least one key and value, but they can be anything you want.

Answer 39

player = {“name”: “Jon snow”, “remaining_lives”: 3}

player = {“name”: “Jon snow”,
“remaining_lives”: 3,
“levels”: [1, 2, 3, 4],
“items”: {“friends”: 3} }

Question 40

What are the 2 ways that you can add an item to your dictionary?

Answer 40

Person[“last_name”] = “snow”

Or person.update({“last_name”: “Snow”})

Question 41

How do you delete something in a dictionary?

Answer 41

del person[“last_name”]

Question 42

What method is used to set or change several keys and their values at once?

Answer 42

.update()

Question 43

What types of data can be used for keys?

Answer 43

String numbers and tuples

Question 44

With the following code:
test_dict = {“a”: 1, “b”: 2, “a”: 3}
what value would test_dict[“a”] return?

Answer 44

It’ll be 3 because the keys are created in order. First it’s 1 and then the 3 is assigned later.

Question 45

TF: Dictionary keys have an order.

Answer 45

False

Question 46

Set the key color to the value ‘red’.

My_car [______ ] = _______

Answer 46

My_car[“color”] = “red”

Question 47

How do you remove a key from a dictionary?

Answer 47

Del

Question 48

What does packing a dictionary mean?

Answer 48

Putting multiple keyword arguments into a single dictionary.

> > > def packing(**kwargs):
print(len(kwargs))
packing(name=”Kenneth”)

This will print {“name”: “Kenneth”}

Question 49

What does unpacking a dictionary mean?

Answer 49

Pulling multiple keys and their values of out of a dictionary to feed them to a function.

> > > my_dict = {‘name’: ‘Kenneth’}
“Hi, my name is {name}!”.format(**my_dict)

“Hi, my name is Kenneth!”

Question 50

Let’s test unpacking dictionaries in keyword arguments.
You’ve used the string .format() method before to fill in blank placeholders. If you give the placeholder a name, though, like in template below, you fill it in through keyword arguments to .format(), like this:
template.format(name=”Kenneth”, food=”tacos”)
Write a function named string_factory that accepts a list of dictionaries as an argument. Return a new list of strings made by using ** for each dictionary in the list and the template string provided.

values = [{“name”: “Michelangelo”, “food”: “PIZZA”},
{“name”: “Garfield”, “food”: “lasagna”}]
template = “Hi, I’m {name} and I love to eat {food}!”

Answer 50

def string_factory(values):
    new_list = []
    for item in values:
        new_list.append(template.format(**item)
    return new_list

Question 51

How do you get the key, value or items of a dictionary?

Answer 51

.keys() - this method returns an iterable of all of the keys in a dictionary. .values() - this method returns an iterable of all of the values in the dictionary.
.items()` - this method is basically a combo of the above two. It returns an iterable of key/value pairs inside of tuples.