Python

Question 1

Filter a list

l = [“ab”, “a”, “c”]
Return items that have a length more than 1

Answer 1

list(filter(lambda x: len(x) > 1, l))

Question 2

Use reduce on a List

Answer 2

from functions import reduce

reduce(lambda a, b: a + b, myList)

This will sum up all the numbers left to right.

reduce(lambda a, b: a if a > b else b, myList)

This will return the max value from list

Question 3

Insert 5 into Index 0 in List

Answer 3

x = [1,2,3,4]

x.insert(0,5)

or

x[0:0] = 5

Question 4

Get character length away from ‘a’

Answer 4

x = ‘f’

ord(x) - ord(‘a’)

Can use to build tuple of 26 letters and add count of letters for an anagram problem (can then compare tuples to see if they match and words are anagrams)

Question 5

Separate word into list of characters

Answer 5

word = “hello”
chars = [*word]

Question 6

Deque and Operations

Answer 6

from collections import deque

x = deque()
x.append()
x.appendleft()
x.pop()
x.popleft))

Question 7

Create decoder with message and alphabet

Answer 7

import string

alpha = string.ascii_lowercase
decorder = dict(zip(msg, alpha))

Question 8

Dictionary comprehension

d = {“a”: 1, “b”: 5, “c”: 10}

Return any key over 2

Answer 8

{k:v for k,v in d.items() if v > 2}

Question 9

Check if number is int or float

Answer 9

(4/2).is_integer()

Question 10

Sum up all dictionary values

Answer 10

sum(d.values())

Question 11

Stack underflow

Answer 11

stack = []
stack[-1]

Question 12

Create a list with x number of spots

Answer 12

l = [0] * x

Question 13

Filter a list

Question 14

Apply function to elements in list

Answer 14

a = [1,2,3,4]
list(map(lambda x: x + 1, a))

Question 15

Apply function to elements in dict

Answer 15

d = {“x”: 1, “a”: 2, “c”: 3}
c = list(map(lambda x: x + 1, d.values()))
new_d = dict(zip(d.keys(), c))

Question 16

What prints out:

nums = [1,2,3,4,5]
for i in range(0, len(nums)):
print(i)

Answer 16

0,1,2,3,4

Question 17

What prints out:

nums = [1,2,3,4,5]
for i in range(0, len(nums) + 1):
print(i)

Answer 17

0,1,2,3,4,5

Question 18

Set starting value of a number without using 0

Answer 18

x = float(“-inf”)

Question 19

Create dict that won’t throw error when accessing key doesn’t exist

Answer 19

from collections import defaultdict

result = defaultdict(list)

Question 20

Scope

Answer 20

Block of code where object remains relevant

local / global

Question 21

*args vs **kwargs

Answer 21

*args = unnamed args passed a tuple

def func1(this, *args):
print(this)
print(args)

func1(1,2,3)
> 1, (2, 3)

**kwargs = keyword args passed as dict

def func2(**kwargs):
print(kwargs)

func2(this=1, that=2)
> {“this”: 1, “that”: 2)

Question 22

Remove duplicates from a file and write to a second file

Answer 22

seen = set()
with open(file1, “r+”) as fromFile, open(file2, “w”) as toFile:
l = fromFile.readlines()
fromFile.seek(0)
fromFile.truncate()
for line in l:
if line in seen:
toFile.write(line)
else:
fromFile.write(line)
seen.add(line)

Question 23

read() vs readline() vs readlines()

Answer 23

read(): returns entire file as str
readline(): returns a single line up to line break
readlines(): reads all lines into a list

Question 24

Split a string into a list of lines

Answer 24

s = “This list\nThat list”
s.splitlines()

Question 25

Sort list with Lambda

Answer 25

l = [“a”, “bb”. “ccc”]
l.sort(key=lambda x: len(x))

Question 26

Delete key from dictionary

Answer 26

del d[‘key_name’]

Question 27

Count number of chars in a string with standard library

Answer 27

from collections import Counter
x = Counter(“thisthat”)

> > Counter({‘t’: 3, ‘h’: 2, ‘i’: 1, ‘s’: 1, ‘a’: 1})

Can then conver to dict:
dict(x)

Question 28

l.sort() vs sorted(l)

Answer 28

l.sort(): Sorts list in-place
sorted(l): Creates new list object that’s sorted

Question 29

Magic methods

Answer 29

aka dunder methods

These methods provide a way to define how objects of a class behave in various contexts, such as arithmetic operations, string representations, comparisons, and more

__str__: defines behavior of ‘str(obj)’
__len__: defines behavior of ‘len(obj)’
__add__(self, other): ‘obj1 + obj2’
__eq__(self, other): ‘obj1 == obj2’
__getitem__(self, key): ‘obj[key]’

Question 30

Python dictionary collisions

Answer 30

Python uses open addressing to handle dict collisions

Question 31

Memory management

Answer 31

• Memory is managed by a private heap space. Interpreter take scare of heap
• Built-in garbage collector

Question 32

Inheritance Types

Answer 32

• Single: When a class inherits only one superclass/parent
• Multiple: When a class inherits multiple superclasses
• Multilevel: When a class inherits a superclass, then another class inherits from it (parent, child, grandparent)
• Hierarchical: When one superclass is inherited by multiple derived/child classes

Question 33

Decorators

Answer 33

Functions that help add functionality to an existing function without changing the structure of the function.

Question 34

Three Types of Control Flow

Answer 34

1. Break: Terminate loop or statement and pass control to next statement
2. Continue: Force execution of the next iteration instead of terminating it
3. Pass: Skip the execution

Question 35

Count number of lines in a file

Answer 35

with open(file_path, ‘r’) as f:
line_count = sum(1 for line in f)

or

with open(file_path, ‘r’) as f:
for count, line in enumerate(fp):
pass
print(‘Total Lines’, count + 1)

Question 36

Drop duplicates in a file using Pandas

Answer 36

import pandas as pd

df = pd.read_csv(fromFile)
df.drop_duplicates(inplace=True)
df.to_csv(toFile)

Question 37

Use sets to get a list of all words in str1 not in str2 and vice versa

Answer 37

words1 = set(str1.split())
words2 = set(str2.split())
result = words1.symmetric_difference(words2)

RETURNS SET

Question 38

Get key with max value from dictionary

Answer 38

d = {‘a’: 10, ‘b’: 5, ‘c’: 15, ‘d’: 7}
max(d, key=d.get)

Question 39

Get key with nth largest value

Answer 39

d = {‘a’: 10, ‘b’: 5, ‘c’: 15, ‘d’: 7}
l = sorted(d, key=d.get, reverse=True)
l[n]

Question 40

Join two sets together

Answer 40

a = set()
b = set()
a.union(b)

Question 41

pass vs continue

Answer 41

continue will exit the iteration of the loop. pass will keep going