Data Types - General Flashcards
Explain what an iterable is and list all the different types of iterables
It’s any object that you can loop over.
String
List
Tuple
Set
Dictionary
range(n)
Which of the below iterables can be sliced?
String
Set
List
Tuple
Dictionary
range(n)
Can be sliced,
String
List
Tuple
range(n)
Can’t be sliced,
Set
Dictionary
What data types can the for loop be used on
All iterables
E.g., for item in iterable:
What iterables can the “in” keyword be used on and why
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:
What iterables can sum() be used on
Any iterable provided all items are numeric…
… thus String is the only iterable that can never utilise sum()
What iterables can max() & min() be used on
All iterables
Though Dictionary operates on the keys
Items MUST be “comparable”
What iterables can len() be used on
All iterables
What iterables can sorted() be used on
All iterables
Items MUST be “comparable”
What iterables can join() be used on
All iterables - provided all items inside the iterable are strings
Using it on a dictionary will join the keys
Join() takes a string seperator, and joins strings from an iterable - seperating thoes strings by that string seperator
What does it mean if an iterables is indexed
Each item in a collection is given a numeric position (an index number)
What does it mean if an iterable is ordered
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
Which of the following iterables are ordered
Set
Tuple
Tuple
a Set is not ordered
Which of the following iterables are indexed
Tuple
Set
Tuple
Which of the following iterables allow duplicates
Set
Tuple
Tuple
What is the main difference between a List and a Tuple
A List is mutable.
A Tuple is immutable.
What does it mean if an iterable is mutable or immutable
Immutable means you cannot modify the object “in place”. To “change” it, you must create a modified copy and reassign it to the variable.
What iterables are immutable
String
Tuple
range()
What iterables are mutable
List
Dictionary
Set
What is the MAIN difference between a List and a String
A list is a collection of any type of items.
A string is a collection of characters only.
Out of the below, which are not ordered,
String
List
Tuple
Set
Dictionary
range(n)
Set is the only one
Out of the below, which don’t allow duplicates,
Tuple
Set
Set
A Dictionary allows duplicate values, but not duplicate k
Out of the below, which are not Indexable,
String
List
Tuple
Set
Dictionary
range(n)
Set
Though a Dictionary is Indexable via Keys rather then Index numbers
How can you find the data type of an object
print(type(object))
x = 10
delete variable x from memory
del x
Can methods like .append(), .remove(), .pop() be used on both mutable & immutanbe iterables
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 the iterable “in place”
Can assignment operators like += & *= be used on both mutable & immutanbe iterables
Yes, but…
On mutable iterables → they change the object in place
On immutable iterables → they create and return a new object
iterable[2] = “d”
Does the above item assignment work on all iterables
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)
del iterable[2]
Does the above deletion work on all iterables
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)
iterable.sort()
Does the above work on all iterables
No, List is the only object with the attribute ‘sort’
sorted(iterable)
Does the above work on all iterables
Yes, because it always returns a new object
What’s the difference between sort() & sorted()
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.
len(iterable)
Does the above work on all iterables
Yes
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]
num_list = list(range(1, 21))
Give 2 effective methods of reversing the order of the List “lst”
lst[ : :-1]
list(reversed(lst))
reversed() creates a “Reversed Iterator” - it does not return a list, hence is must be converted to, in this case, a List.
What is the difference between the below,
lst[ : :-1]
reversed(lst)
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()
what is the main advantages of using,
list(reversed(lst))
instead of ,
lst[ : :-1]
list(reversed(lst)) is more memory efficient, so usefull for large lists.
What is the difference between an “Iterator” & an “Iterable”
(In layman’s terms)
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
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))
Using a List with .join() is quicker & more memory-efficient than a String with +=
Because Strings are immutable, += creates a new String for each iteration - which can become very inefficient with long Strings
for i in iterable:
print(iterable[i])
What does the above print
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)
for i in iterable:
print(i)
For which iterables can you use the above
All Iterables
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.
for i in range(len(iterable)):
print(i)
numbers = [0, 3, 4, 5]
sqa_num = []
for num in numbers:
sqa_num += num ** 2
What will the above return
TypeError
In this case “+=” is attempting to “extend” the List with another Iterable
You should use .append() instead to add a single number
a = 1
b = 2
c = 3
Modify the above assignments to be in a single line
a, b, c = 1, 2, 3
There a 2 variables a & b. Swap their assigned values without using a temporary variable
a, b = b, a
There are 3 vaiables, a, b & c
In a single line, assign b to a, c to b & a to c
a, b, c = b, c, a
lst = [1, 2, 3]
In a single line, re-arrange “lst” to the below
[3, 1, 2]
lst[0], lst[1], lst[2] = lst[1], lst[2], lst[3]
a, b = divmod(10, 3)
What does the above do
It divides 10 by 3 and assigns:
1) “a” the quotient → 10 // 3 = 3
2) “b” the remainder → 10 % 3 = 1
for i in range(len(“abc”)):
print(i)
What’s a cleaner and more Pythonic way to write the above
for i, item in enumerate(“abc”):
print(i)
Enumerate() actually retrieves both the index number and the item value, hence print(i, item) will print both
An easy way to check if all the characters in a string are digits
str.isdigit()
Returns True or False
“123”.isdigit()
What deos the above do
Checks if ALL characters in a String are digits
Returns True or False
An easy way to compare 2 Lists for similarity, returning True or False for each item
for a, b in zip(list1, list2):
if a != b:
return False
What does any() do
any() returns True if any element is truthy
for word in words:
if “x” in word:
return True
return False
Write the above using the any() function
return any(“x” in word for word in words)
What does all() do
all() returns True if all elements are truthy
for c in password:
if c.isdigit() == False:
return False
return True
Write the above using the all() function
return all(c.isdigit() for c in password)
Using the any() function, check if any number is even in a List of numbers
any(num % 2 == 0 for num in nums)
Using the all() function, check if all numbers in a List of numbers are between 1 and 10
all(1 <= n <= 10 for n in nums)
