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Flashcards in 4 Lists Deck (22)
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1
Q
A = [ [ A, B, C], [1, 2, 3] ]
B = [ 9, 8, 7, 6, 5 ]

How many list values and items are in A?
What is A [0][1]?

What is the index range of B?

A

A = [ [ A, B, C], [1, 2, 3] ]
-> 2x list values
-> 2x lists with 3 items each
A [0][1] -> 0 indicates the first list value ABC, 1 indicates the index of that list, which is index and thus item B

B = [ 9, 8, 7, 6, 5 ]
-> index range 0 to 4

2
Q

In a slice the first integer is the index where the slice […]. The second integer is where the slice […]. A slice […], but will not […] the value at the second index.

A

In a slice the first integer is the index where the slice [starts]. The second integer is where the slice [ends]. A slice [goes up to], but will not [include] the value at the second index.

3
Q
A = [ A, B, C]
How do you:
    replace
    add
    delete items from a list
A

A = [ A, B, C]
Replace:
A[0] = ‘D’

Add:
A.append(‘D’)
A.insert(‘2, D’)

Delete:
A.remove(‘D’) -> When you know the value
del A[0] -> When you know the index

4
Q

A= [‘pens’, ‘staplers’, ‘flamethrowers’]

How can a for loop access and print out the indexes of a loop combined with their item value? (2x)

A

1.
A= [‘pens’, ‘staplers’, ‘flamethrowers’]
for x in range(len(A) ):
print( str(x) + A[x] )

Output:
0pens
1staplers
2flamethrowers

  1. enumerate() function returns two values: The first one is the index of the item, the second one the item itself
    for index, item in enumerate(A):
    print(str(index) + item)
5
Q

How can you find out if a certain value is in a list?

-> myPets example

A

With the ‘in’ and ‘not in ‘ operators which will return False or True

myPets = ['Zophie', 'Pooka', 'Fat-tail']
print('Enter a pet name:')
name = input()
if name not in myPets:
    print('I do not have a pet named ' + name)
else:
    print(name + ' is my pet.')
6
Q

What is the Multiple Assignment Trick, what is a preqrequisite for it and how is it called technically?

A

Instead of assigning values to items in a list one by one, they can be assigned simulteanously.
Preqrequisite : number of variables and length of list must be equal
Technical term: Tuple Unpacking

> > > cat = [‘fat’, ‘gray’, ‘loud’]
size, color, disposition = cat
size
‘fat’

7
Q

What is the long version of:
»> import random
»> random.choice(listA)

How can you randomly reorder items in a list?

A

listA[random.randint(0, len(listA)-1)]

Reorder:
random.shuffle(listA)

8
Q

Name the 5 Augmented Assignment Operators

A
spam += 1
spam -= 1
spam *= 1
spam /= 1
spam %= 1
9
Q
>>> bacon = 'Hello'
>>> id(bacon)
44491136
>>> bacon += ' world!' 
>>> id(bacon) 

What happens to the ID of bacon and why?

A

Strings are immutable. Thus, the “change” leads to the creation of a new string with a new ID

10
Q
>>> bacon = ['cat', 'dog'] 
>>> id(bacon )
35152584
>>> bacon .append('moose') # modifies the list "in place".
>>> id(bacon ) 

What happens to the ID of bacon and why?

A

Lists are mutable. So the object is “modified in place”, altering the existing object instead of creating a new one. The ID stays the same.

11
Q

What can be modified in place and how?

A

Mutable data types, such as lists.
For that you can use list methods, e.g.
sort(), remove(), extend(), append(), reverse()

12
Q

What is the purpose of Python´s copy.module?

A

When a function is called, the values of the arguments are copied to the parameter variables. For lists & dict´s this means a copy of the reference is used for the parameter.
To create entirely new lists, and not copies to former references, you can use the copy module.

13
Q

What is the difference between copy and deepcopy?

A
copy = for lists
deepcopy = for lists that contain lists as well
14
Q

What is a tuple

A

A tuple is an immutable sequence data type. In contrast to lists it is written with () instead of []
egg = (A, B, C)

A tuple with a single item is distinct from a strin because of its ‘,’
egg = (‘hello’,) instead of ‘hello’

just like all immutable data types, tuples cannot be changed

15
Q

What are lists?

A

Lists are a mutable sequence data type, indicated by = [ ]. Variables can store references to lists (not list values directly!!!).

Changes to a list might change other variables in the code

16
Q

How would you assign the value ‘hello’ as the third value in a list stored in a variable named spam? (Assume spam contains [2, 4, 6, 8, 10].)

A

spam[2] = ‘hello’

17
Q

Imagine spam = [a, b, c, d]

  1. What does spam[int(int(‘3’ * 2) // 11)] evaluate to?
  2. What does spam[-1] evaluate to?
  3. What does spam[:2] evaluate to?
A

Imagine spam = [a, b, c, d]
1. What does spam[int(int(‘3’ * 2) // 11)] evaluate to?
33 / 11 = 3 -> spam[3] -> ‘d’
2. What does spam[-1] evaluate to?
‘d’
3. What does spam[:2] evaluate to?
‘a’, ‘b’ –> up to 2, so ‘c’ is not included!

18
Q

Imagine bacon = [3.14, ‘cat’, 11, ‘cat’, True]

  1. What does bacon.index(‘cat’) evaluate to?
  2. What does bacon.append(99) make the list value in bacon look like?
  3. What does bacon.remove(‘cat’) make the list value in bacon look like?
A

Imagine bacon = [3.14, ‘cat’, 11, ‘cat’, True]

  1. What does bacon.index(‘cat’) evaluate to?
    ‘1’
  2. What does bacon.append(99) make the list value in bacon look like?
    bacon = [3.14, ‘cat’, 11, ‘cat’, True, 99]
  3. What does bacon.remove(‘cat’) make the list value in bacon look like?
    bacon = [3.14, 11, ‘cat’, True, 99]
19
Q

What is the difference between the append() and insert() list methods?

A

append() adds to the end of the list

insert() adds to the specified index

20
Q

Name a few ways that list values are similar to strings

A

Strings start with ‘’, lists with [ ]
Strings store series of letters, lists of items
both letters and items can be accessed with egg[i]
both can be *multiplied or +concatenated

21
Q

How do you type the tuple value that has just the integer value 42 in it?

A

egg = (42,)

-> the , is important!

22
Q

How can you get the tuple form of a list value? How can you get the list form of a tuple value?

A

> > > tuple([‘cat’, ‘dog’, 5])
(‘cat’, ‘dog’, 5)
list((‘cat’, ‘dog’, 5))
[‘cat’, ‘dog’, 5]