Data Types - General - Beginner Concepts

Question 1

Explain what an iterable is and list all the different types of iterables

Answer 1

It’s any object that you can loop over.

String
List
Tuple
Set
Dictionary
range(n)

Question 2

Which of the below iterables can be sliced?

String
List
range(n)

Answer 2

All of these can be sliced

Question 3

What data types can the for loop be used on

Answer 3

All iterables

E.g., for item in iterable:

Question 4

What iterables can the “in” keyword be used on and why

Answer 4

All iterables - because if an object is iterable, Python can loop through it to check for membership — which is what “in” does

E.g., if x in iterable:

Question 5

What iterables can sum() be used on

Answer 5

Any iterable provided all items are numeric…

… thus String is the only iterable that can never utilise sum()

Question 6

What iterables can max() & min() be used on

Answer 6

All iterables

Though Dictionary operates on the keys

Items MUST be “comparable”

Question 7

What iterables can len() be used on

Answer 7

All iterables

Question 8

What iterables can sorted() be used on

Answer 8

All iterables

Items MUST be “comparable”

Question 9

What iterables can join() be used on

Answer 9

All iterables - provided all items inside the iterable are strings

Join() takes a string seperator, and joins strings from an iterable - seperating thoes strings by that string seperator

Question 10

What does it mean if an iterables is indexed

Answer 10

Each item in a collection is given a numeric position (an index number)

Question 11

What does it mean if an iterable is ordered

Answer 11

Items stay in the order you added them

If an iterable is unordered, Python may reorder the items immediately upon creation or when operations are performed

Question 12

Complete this table

Answer 12

Question 13

Complete this table

Answer 13

Question 14

What is the main difference between a List and a Tuple, and why might this make you prefer to use a Tuple instead of a List

Answer 14

A List is mutable.
A Tuple is immutable.

Use a tuple when your data should not changed “in place”

Question 15

What does it mean if an iterable is mutable or immutable

Answer 15

Immutable means you cannot modify the object “in place”. To “change” it, you must create a modified copy and reassign it to the variable.

Question 16

What is the MAIN difference between a List and a String

Answer 16

A list is a collection of any type of items.
A string is a collection of characters only.

Question 17

How can you find the data type of an object

Answer 17

print(type(object))

Question 18

x = 10

delete variable x from memory

Answer 18

del x

Question 19

Can methods like .append(), .remove(), .pop() be used on both mutable & immutanbe iterables

Answer 19

No, only on mutable iterables.

With a String, for example, these won’t work even if you attempt to store the result in a variable.

Because these methods try to modify iterables in place

Question 20

Can assignment operators like += & *= be used on both mutable & immutable iterables

Answer 20

Yes, but…

On mutable iterables → they change the object in place

On immutable iterables → they create and return a new object

Question 21

iterable[2] = “d”

Does the above item assignment work on all iterables

Answer 21

No, it only works on iterables that are mutable and support indexing.

Hence, it only works on List & Dictionary (though with Dictionary, “2” is the key and “d” is the value)

Question 22

del iterable[2]

Does the above deletion work on all iterables

Answer 22

No, it only works on iterables that are both mutable and indexable.

Hence, it only works on List & Dictionary (though with Dictionary, it deletes the key)

Question 23

iterable.sort()

Does the above work on all iterables

Answer 23

No, List is the only object with the attribute ‘sort’

Question 24

sorted(iterable)

Does the above work on all iterables

Answer 24

Yes, because it always returns a new object

Question 25

What's the difference between sort() & sorted()

Answer 25

sort() is really .sort() & it's a method of the "List" iterable and can only be used on Lists - it modifies the List "in place". sorted() always returns a new object, hence can be used on any iterable.

Question 26

len(iterable) Does the above work on all iterables

Answer 26

Yes

Question 27

What is an easier way to do the below, num_list = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20]

Answer 27

num_list = list(range(1, 21))

Question 28

Give 2 effective methods of reversing the order of the List "lst"

Answer 28

lst[ : :-1] list(reversed(lst)) ## Footnote reversed() creates a "Reversed **Iterator**" - it does not return a list, hence is must be converted to, in this case, a List.

Question 29

What is the difference between the below, lst[ : :-1] reversed(lst)

Answer 29

lst[ : :-1] returns a new reversed List reversed(lst) returns a "Reversed **Iterator**" - it does not create a new List unless you wrap it with list()

Question 30

what is the main advantages of using, list(reversed(lst)) instead of , lst[ : :-1]

Answer 30

list(reversed(lst)) is more memory efficient, so usefull for large lists.

Question 31

What is the difference between an "Iterator" & an "Iterable" (In layman's terms)

Answer 31

Iterables are collections of data - like String, List, Set, Tuple, Dictionary, range() An Iterator is like instructions for **how** to cycle through those items In a vending machine, the snacks are the **Iterables** and the retreival mechanism is the **Iterator**

Question 32

Which is better & why result = "" for char in "String": result += char * 2 print(result) vs result = [] for char in "String": result.append(char * 2) print(''.join(result))

Answer 32

Using a List with .join() is quicker & more memory-efficient than a String with += ## Footnote Because Strings are immutable, += creates a new String for each iteration - which can become very inefficient with long Strings

Question 33

result = "" for char in "String": result += char * 2 print(result) Without using a Generator Expression, write a script that does the above in a **quicker** & **more memory-efficient** way

Answer 33

result = [] for char in "String": result.append(char * 2) print("".join(result)) ## Footnote The original version (String Concatenation with +=) creates a new string object for every loop. The "List" method does not create a new object for every loop - instead .append adds new items to the list "in place".

Question 34

for i in iterable: print(iterable[i]) What does the above print

Answer 34

TypeError This treats "i" like it's an index, but it actually refers to an item in the collection "iterable". If you want to print the Item, it should be typed as below, for i in iterable: print(i)

Question 35

for i in iterable: print(i) For which iterables can you use the above

Answer 35

All Iterables

Question 36

for i in iterable: print(i) The above returns the **Items** in the iterable. How should the above be modified to return the **Index** of the items.

Answer 36

for i in range(len(iterable)): print(i)

Question 37

numbers = [0, 3, 4, 5] sqa_num = [] for num in numbers: sqa_num += num ** 2 What will the above return

Answer 37

TypeError In this case "+=" is attempting to "extend" the List with another **Iterable** You should use .append() instead to add a single number

Question 38

a = 1 b = 2 c = 3 Modify the above assignments to be in a single line

Answer 38

a, b, c = 1, 2, 3

Question 39

There a 2 variables a & b. Swap their assigned values without using a temporary variable

Answer 39

a, b = b, a

Question 40

There are 3 vaiables, a, b & c In a single line, assign b to a, c to b & a to c

Answer 40

a, b, c = b, c, a

Question 41

lst = [1, 2, 3] In a single line, re-arrange "lst" to the below [3, 1, 2]

Answer 41

lst[0], lst[1], lst[2] = lst[1], lst[2], lst[3]

Question 42

a, b = divmod(10, 3) What does the above do

Answer 42

It divides 10 by 3 and assigns: 1) "a" the quotient → 10 // 3 = 3 2) "b" the remainder → 10 % 3 = 1

Question 43

for i in range(len("abc")): print(i) What's a cleaner and more Pythonic way to write the above

Answer 43

for i, item in enumerate("abc"): print(i) ## Footnote Enumerate() actually retrieves both the index number and the item value, hence print(i, item) will print both

Question 44

An easy way to check if **all** the characters in a string are digits

Answer 44

str.isdigit() | Returns True or False

Question 45

"123".isdigit() What deos the above do

Answer 45

Checks if **ALL** characters in a String are digits | Returns True or False

Question 46

An easy way to compare 2 Lists for similarity, returning True or False for each item

Answer 46

for a, b in zip(list1, list2): if a != b: return False

Question 47

names = ['Link', 'Zelda', 'Ganon'] scores = [95, 87, 78] zipped = zip(names, scores) print(list(zipped)) What does the above print, and why does "zipped" need to first be converted to a List before printing

Answer 47

[('Link', 95), ('Zelda', 87), ('Ganon', 78)] It must first be converted to a List because zip() returns an "iterator", not an "iterable" ## Footnote zip() essentially pairs up elements from multiple sequences (e.g., lists, tuples, etc.) by their position — into tuples

Question 48

char = ['a', 'b', 'c'] n = [1, 2, 3] Turn the above into... [('a', 1), ('b', 2), ('c', 3)]

Answer 48

result = list(zip(char, n)) ## Footnote zip() must first be converted to a List because zip() returns an "iterator", not an "iterable"

Question 49

list1 = [1,2,3] list2 = [4,5,6] for a, b in zip(list1, list2): print(b) What does the above print

Answer 49

4 5 6

Question 50

What does any() do

Answer 50

any() returns True if **any** element is truthy

Question 51

for word in words: if "x" in word: return True return False Write the above using the any() function

Answer 51

return any("x" in word for word in words)

Question 52

Return True if any score is greater than 50 in "scores" scores = [35, 42, 75]

Answer 52

if any(score > 50 for score in scores): Return True

Question 53

Return True if any field is blank in "fields" fields = ["Alice", "", "email@example.com"]

Answer 53

if any(field == "" for field in fields): return True

Question 54

Return True if any word from "words" is in "text" words = ["python", "code"] text = "I love to code."

Answer 54

return = any(word in text for word in words) print(return) ## Footnote The above is the "generator expression" of... for word in words: if word in text: print(True) break It might be easier to think of it in reverse "for word in words" - any() returns True if **any** "word in text" == True

Question 55

What does all() do

Answer 55

all() returns True if **all** elements are truthy

Question 56

for c in password: if c.isdigit() == False: return False return True Write the above using the all() function

Answer 56

return all(c.isdigit() for c in password)

Question 57

Using the any() function, check if any number is even in "nums" nums = [1,2,3,4,5,6,7,8,9]

Answer 57

if any(num % 2 == 0 for num in nums): return True

Question 58

Using the all() function, check if all numbers in "nums" are between 1 and 10 nums = [3,4,5,6,7]

Answer 58

if all(1 <= n <= 10 for n in nums) return True

Question 59

text = "World" return reversed(text) Why does the above not work & how can you fix it

Answer 59

reversed(text) returns a reversed iterator, not a string You can convert the reversed iterator into a string using "".join(reversed(text)) str(reversed(text)) won't work because reversed(text) does not return the actual characters in reverse ## Footnote However, a more Pythonic way to reverse a string is simply to use text[ : :-1]

Question 60

list(reversed(lst)) str(reversed(text)) Which of the above will work & why/why-not

Answer 60

reversed() returns an iterator str() does not loop through iterables. list() does! str() just converts the object itself to a string ## Footnote You can convert the reversed iterator into a string using "".join(reversed(text)) But a more Pythonic way to reverse a string is text[ : :-1]

Question 61

What is a "Sequence"

Answer 61

An **Ordered** iterable ## Footnote E.g., **Includes;** String, List, Tuple, range() **Excludes;** Set, Dict

Question 62

a = [1, 2, 3] b = a b.append(4) print(a) print(b) What does a & b print

Answer 62

a = [1, 2, 3, 4] b = [1, 2, 3, 4] ## Footnote Both the same, because **both point to the same List in memory** (b = a) and Lists are **mutable**. This is why mutability is important, because by amending "b", you are also amending "a", which could cause bugs in your code.

Question 63

a = (1, 2, 3) b = a b.append(4) print(a) print(b) What does a & b print

Answer 63

Attribute Error ## Footnote Tupes are immutable, so cannot be amended in place

Question 64

a = "hello" b = a b = b + " world" print(a) print(b) What does a & b print

Answer 64

a = hello b = hello world ## Footnote Because Strings are immutable, even though "b = a", "a" remains unchanged

Question 65

Lists are mutable, Tuples are immutable. Is this the only difference?

Answer 65

*Mostly*, yes However, note that, for Tuples, this means that only the methods below are available, .count() .index()

Question 66

a = (1, 2, 3) b = a b = b + (4,) print(a) print(b) What does a & b print

Answer 66

a = (1, 2, 3) b = (1, 2, 3, 4) ## Footnote Because Tuples are immutable, even though "b = a", "a" remains unchanged

Question 67

a = [1, 2, 3] b = a b.append(4) If you want to copy "a" to "b" so you *can* amend "b" yet leave "a" untouched, the above will not work, since "b = a" means **both** a & b refer to the same place in memory, so changing one changes the other. Give 2 methods of "safely" making a "shallow" copy of a to b

Answer 67

b = a.copy() or b = a[ : ] ## Footnote The seconds method slices the entire list