#1 – Core Python Concepts

Question 1

What does enumerate() do in a for loop?

Answer 1

It allows you to loop over an iterable and get both the index and the item.

for i, val in enumerate(['a', 'b', 'c']):
    print(i, val)

0 a 1 b 2 c

Question 2

What does zip() do in Python?

Answer 2

It pairs elements from two or more iterables into tuples.

for a, b in zip([1, 2], ['x', 'y']):
    print(a, b)

Question 3

What is list comprehension in Python?

Answer 3

A concise way to create a list using a single line of code.
squares = [x**2 for x in range(10) if x % 2 == 0]

Question 4

What is dict comprehension in Python?

Answer 4

A compact way to create a dictionary from an iterable.
mapping = {c: ord(c) for c in 'abc'}

Question 5

What are *args used for in a function definition?

Answer 5

*args lets you pass a variable number of positional arguments as a tuple.

def func(*args):
    print(args)
func( 2, 3)

Question 6

What are **kwargs used for in a function definition?

Answer 6

**kwargs lets you pass a variable number of keyword arguments as a dictionary.
Example:

def func(**kwargs): 
    print(kwargs)
func(a=1, b=2)
{'a': 1, 'b': 2}

Question 7

What will the following code output?

def func(a, *args, **kwargs):
    print(a)
    print(args)
    print(kwargs)
func(1, 2, 3, x=4, y=5)

Answer 7

1
(2, 3)
{‘x’: 4, ‘y’: 5}

Question 8

What is a lambda function in Python?

Answer 8

wynik: [(2, ‘a’), (3, ‘b’), (1, ‘c’)]

An anonymous (unnamed) function defined with the lambda keyword.

data = [(1, 'c'), (2, 'a'), (3, 'b')]
sorted(data, key=lambda x: x[1])

wynik: [(2, ‘a’), (3, ‘b’), (1, ‘c’)]