Python Snippets

Question 1

Python Snippet

Answer 1

Explanation

Question 2

if not nums:

Answer 2

Check if the list is empty.

Question 3

if x in my_set:

Answer 3

Check if ‘x’ is an element in the set.

Question 4

for i, val in enumerate(arr):

Answer 4

Loop with both index and value.

Question 5

nums = [x for x in arr if x % 2 == 0]

Answer 5

List of even numbers from ‘arr’.

Question 6

return sorted(arr)

Answer 6

Return a new sorted list.

Question 7

arr.sort()

Answer 7

Sort the list in-place.

Question 8

from collections import Counter

Answer 8

Import Counter to count elements.

Question 9

Counter(arr)

Answer 9

Create frequency dictionary of ‘arr’.

Question 10

’‘.join(chars)

Answer 10

Join list of characters into a string.

Question 11

list(map(int, input().split()))

Answer 11

Read integers from input.

Question 12

while stack:

Answer 12

Loop while stack is not empty.

Question 13

stack.append(x)

Answer 13

Push ‘x’ onto the stack.

Question 14

stack.pop()

Answer 14

Pop the top element from the stack.

Question 15

if not stack:

Answer 15

Check if stack is empty.

Question 16

set1 & set2

Answer 16

Intersection of two sets.

Question 17

set1 | set2

Answer 17

Union of two sets.

Question 18

set1 - set2

Answer 18

Elements in set1 but not in set2.

Question 19

nums[::-1]

Answer 19

Reverse a list.

Question 20

s[::-1]

Answer 20

Reverse a string.

Question 21

any(x > 10 for x in arr)

Answer 21

Check if any element is > 10.

Question 22

all(x > 0 for x in arr)

Answer 22

Check if all elements are > 0.

Question 23

{i: 0 for i in range(5)}

Answer 23

Create a dictionary with values 0.

Question 24

for key in my_dict:

Answer 24

Loop through dictionary keys.

Question 25

my_dict.get(k, 0)

Answer 25

Get value for key with default 0.

Question 26

try: ... except:

Answer 26

Handle exceptions safely.

Question 27

import heapq

Answer 27

Import heapq module.

Question 28

heapq.heappush(heap, x)

Answer 28

Add element to heap.

Question 29

heapq.heappop(heap)

Answer 29

Remove smallest element.

Question 30

heapq.heapify(arr)

Answer 30

Turn list into a heap.

Question 31

defaultdict(list)

Answer 31

Dictionary with list as default.

Question 32

isinstance(x, list)

Answer 32

Check if 'x' is a list.

Question 33

lambda x: x**2

Answer 33

Short function that squares x.

Question 34

sorted(arr, key=len)

Answer 34

Sort by length of elements.

Question 35

sorted(arr, reverse=True)

Answer 35

Sort in descending order.

Question 36

filter(lambda x: x > 0, arr)

Answer 36

Keep only positive elements.

Question 37

map(str, nums)

Answer 37

Convert numbers to strings.

Question 38

zip(list1, list2)

Answer 38

Pair elements from two lists.

Question 39

list(zip(*matrix))

Answer 39

Transpose a matrix.

Question 40

a, b = b, a

Answer 40

Swap values of a and b.

Question 41

x = a or b

Answer 41

Use 'a' if truthy, else 'b'.

Question 42

x = a and b

Answer 42

Use 'b' if 'a' is truthy, else 'a'.

Question 43

my_dict.items()

Answer 43

Key-value pairs from dict.

Question 44

my_dict.keys()

Answer 44

Keys of the dictionary.

Question 45

my_dict.values()

Answer 45

Values of the dictionary.

Question 46

with open('file.txt') as f:

Answer 46

Open file and close it automatically.

Question 47

yield x

Answer 47

Return value from generator.

Question 48

def gen(): yield from range(5)

Answer 48

Generator that yields 0–4.

Question 49

re.findall(r'\d+', s)

Answer 49

Find all numbers in string.

Question 50

import re

Answer 50

Import regex module.

Question 51

re.sub(r'\s+', ' ', s)

Answer 51

Replace multiple spaces with one.

Question 52

s.strip()

Answer 52

Trim whitespace.

Question 53

s.lower()

Answer 53

Convert string to lowercase.

Question 54

s.upper()

Answer 54

Convert string to uppercase.

Question 55

s.startswith('abc')

Answer 55

Check if string starts with 'abc'.

Question 56

s.endswith('xyz')

Answer 56

Check if string ends with 'xyz'.

Question 57

len(set(s)) == len(s)

Answer 57

Check if all characters are unique.