Introduction to Python Flashcards

Question

Are Tuples mutable?

Answer 1

tuples are immutable - you can't add and remove items from tuples, or sort them in place.

Answer 2

dimensions = 52, 40, 100 length, width, height = dimensions print("The dimensions are {} x {} x {}".format(length, width, height)) In the second line, three variables are assigned from the content of the tuple dimensions. This is called tuple unpacking. You can use tuple unpacking to assign the information from a tuple into multiple variables without having to access them one by one and make multiple assignment statements.

Answer 3

A set is a data type for mutable unordered collections of unique elements.

Answer 4

No numbers = [99, 100, 1, 3, 4, 99, 100] unique_nums = set(numbers) print(unique_nums) Output {1, 3, 99, 100, 4}

Answer 5

using curly braces { }

Answer 6

add elements to sets using the add method, remove elements using the pop method Note: pop an element from a set, a random element is removed.

Answer 7

No Set is unordered.

Answer 8

Sample data set1 = set(range(1000)) set2 = set(range(500, 1500)) list1 = list(set1) list2 = list(set2) Union start_time = time.time() union_set = set1.union(set2) start_time = time.time() union_list = list(set(list1 + list2))

Answer 9

intersection_set = set1.intersection(set2) intersection_list = [x for x in list1 if x in set2]

Answer 10

difference_set = set1.difference(set2) difference_list = [x for x in list1 if x not in set2]

Answer 11

A dictionary is a mutable data type that stores mappings of unique keys to values. In general, dictionaries look like key-value pairs, separated by commas: {key1:value1, key2:value2, key3:value3, key4:value4, ...}

Answer 12

Using curly braces { }

Answer 13

No. Both Set and dictionaries are created using the same curly braces { }

Answer 14

Yes. Key part is immutable. Value part is mutable.

Answer 15

Using the key value passed using the Square brackets elements = {"hydrogen": 1, "helium": 2, "carbon": 6} print(elements["helium"]) Alternatively, print(elements.get("helium")) unlike square brackets will give you a "KeyError", get returns None (or a default value of your choice) if the key isn't found.

Answer 16

Yes. print("carbon" in elements)

Answer 17

is ==> evaluates if both sides have the same identity is not ==> evaluates if both sides have different identities n = elements.get("dilithium") print(n is None) print(n is not None) output: True False

Answer 18

include containers in other containers to create compound data structures. For example, this dictionary maps keys to values that are also dictionaries! We can access elements in this nested dictionary like this.

Answer 19

zip returns an iterator that combines multiple iterables into one sequence of tuples. Each tuple contains the elements in that position from all the iterables. For example, printing list(zip(['a', 'b', 'c'], [1, 2, 3])) would output [('a', 1), ('b', 2), ('c', 3)]. for letter, num in zip(letters, nums): print("{}: {}".format(letter, num))

Answer 20

exactly opposite of zip. unzip a list into tuples using an asterisk. some_list = [('a', 1), ('b', 2), ('c', 3)] letters, nums = zip(*some_list)

Answer 21

enumerate is a built in function that returns an iterator of tuples containing indices and values of a list. You'll often use this when you want the index along with each element of an iterable in a loop. letters = ['a', 'b', 'c', 'd', 'e'] for i, letter in enumerate(letters): print(i, letter) output: 0 a 1 b 2 c 3 d 4 e

Answer 22

List comprehensions allow us to create a list using a for loop in one step. You create a list comprehension with brackets [].

Answer 23

capitalized_cities = [] for city in cities: capitalized_cities.append(city.title()) can be reduced to: capitalized_cities = [city.title() for city in cities]

Answer 24

After the iterable, you can use the if keyword to check a condition in each iteration. squares = [x**2 for x in range(9) if x % 2 == 0] sets squares equal to the list [0, 4, 16, 36, 64], as x to the power of 2 is only evaluated if x is even. ==> Here if acts as a filter of the for-loop. If you would like to add else, you have to move the conditionals to the beginning of the listcomp, right after the expression, like this. squares = [x**2 if x % 2 == 0 else x + 3 for x in range(9)] ==> Here if acts as a conditional expression of the for-loop.