Python

Question 1

What are the logical operators in Python

Answer 1

and, or, and not

Question 2

What are the bitwise operators in Python

Answer 2

&, |, and ^

Question 3

What are the priorities of the sequence operations in Python

Answer 3

x in s, x not in s
s + t, s * n or n * s
s[i], s[i:j], s[i:j:k]
len(s)
min(s)
max(s)
s.index(x[, i[, j]])
s.count(x)

Question 4

What sequence operation is used to test if an item exists in a sequence

Answer 4

x in seq True if x exists in seq, False otherwise
x not in seq False if x exists in seq, True otherwise

Question 5

What sequence operation is used to concatenate two sequences

Answer 5

seq1 + seq2

Question 6

What sequence operation is used to repeat a sequence

Answer 6

seq * n or n*seq

Question 7

What sequence operation is used to return an element or slice of a sequence

Answer 7

seq[i] return the ith element
seq[i:j] slice from i to j, not including j
seq[i:j:k] slice from i to j, not including j, with step k

Question 8

What sequence operation is used to get the length of a sequence

Answer 8

len(seq) the length of seq

Question 9

What sequence operation is used to get the minimum value of a sequence

Answer 9

min(seq) the smallest item of seq

Question 10

What sequence operation is used to get the maximum value of a sequence

Answer 10

max(seq) the largest item of seq

Question 11

What sequence operation returns the index of an object in a sequence

Answer 11

seq.index(x[,i[, j]]) index of the first occurrence of x (at or after index i and before index j)

Question 12

What sequence operation is counts the number of occurrences of an object in a sequence

Answer 12

seq.count(x) total number of occurrences of x in seq

Question 13

What are the basic sequence types in Python

Answer 13

list, tuple, range, str, bytes, and bytearray

Question 14

What are Falsey values in Python

Answer 14

Constants defined to be false: None and False
Numeric types that are zero: 0, 0.0, 0j, Decimal(0), Fraction(0, 1)
Empty sequences and collections: '', (), [], {}, set(), range(0)

Question 15

What are Truthy values in Python

Answer 15

Constants defined to be true: True
Numeric types that are not zero
Non-empty sequences or collections

Question 16

What data types are valid keys for a hash map/dictionary

Answer 16

Objects: Integer, Float, String, Boolean
Immutable sequences: String, Tuple, Range, Frozenset

Question 17

For small inputs, an array can be faster than a hash map. Why?

Answer 17

There is overhead associated with a hash map such as the hash function

Question 18

When designing a hash map what are some good design choices

Answer 18

1. Use a prime number in your hash function which helps spread the keys more evenly
2. Design a hash function that spreads hashes evenly to avoid collisions
3. Implement a method to handle collisions: chaining or open addressing

Question 19

How can you use a list to simulate a stack

Answer 19

stack = []
stack.append(3) # push
stack.pop() # pop
len(stack) # num of element
stack[-1] # peek
if not stack # check empty

Question 20

How can you simulate a queue

Answer 20

# Initialize a queue
from collections import deque
queue = deque()
queue = deque([1,2,3])

queue.append(4) # Enqueue
queue.pop()     # deque
queue[0]        # peek
len(queue)      # get size

Question 21

What built-in function returns the absolute value of a number

Answer 21

abs(x)

>>> abs(-10)
10
>>> abs(-3.145)
3.145

Question 22

What built-in function converts a number to a binary string

Answer 22

bin(x)

>>> bin(10)
'0b1010'
>>> format(10,'b')
'1010'

Question 23

What built-in Python function returns the character corresponding to a given Unicode code point (integer)?

Answer 23

chr(i)

>>> chr(97)
'a'
>>> chr(ord('a'))
'a'

Question 24

What built-in function takes two (non-complex) numbers as arguments and returns a pair of numbers consisting of their quotient and remainder when using integer division

Answer 24

divmod(a, b)

>>> divmod(30,4)
(7, 2)

Question 25

Which built-in Python function returns an iterator that yields pairs of index and value from an iterable?

Answer 25

`enumerate(iterable, start=0)` ``` >>> list(enumerate(['a','b','c'])) [(0, 'a'), (1, 'b'), (2, 'c')] ```

Question 26

What built-in function returns a floating point number from a number or a string

Answer 26

`float(x)` ``` >>> float(1) 1.0 >>> float(" -1.345\n") -1.345 ```

Question 27

What built-in function returns a new frozenset object

Answer 27

`frozenset(iterable=set())` ``` >>> frozenset([1,2,2,3,4,5,5]) frozenset({1, 2, 3, 4, 5}) ```

Question 28

What built-in function returns the hash value of an object

Answer 28

`hash(object)` ``` >>> hash('foo') 9059890961789401645 >>> hash(1) 1 >>> hash(2) 2 >>> hash(True) 1 >>> hash(False) 0 >>> hash((1,2,5)) 2143910794424799510 ```

Question 29

What built-in function returns the hexadecimal string of an integer

Answer 29

`hex(x)` ``` >>> hex(420) '0x1a4' >>> format(420, 'x') '1a4' >>> format(420, 'X') '1A4' ```

Question 30

What built-in function returns an integer object from a number or a string

Answer 30

`int(number=0)` `int(string, base=10)` ``` >>> int("1234") 1234 >>> int(123.45) 123 >>> int("1234") 1234 >>> int(' -12_345\n') -12345 >>> int('0x1a4', 0) 420 >>> int('0b110100100', 0) 420 >>> int('110100100', 2) 420 ```

Question 31

What built-in function returns the length (number of items) in an object

Answer 31

`len(s)`

Question 32

What built-in function returns a new list object from an iterable

Answer 32

`list(iterable)`

Question 33

Which built-in Python function returns a map object that applies a function to items from one or more iterables?

Answer 33

`map()` **Explanation:** If multiple iterables are provided, the function must accept the same number of arguments. The function is applied to elements from each iterable in parallel. **Example:** ``` >>> list(map(lambda x: x * 2, [1, 2, 3])) [2, 4, 6] >>> list(map(lambda x, y: x + y, [1, 2, 3], [4, 5, 6])) [5, 7, 9] ```

Question 34

What built-in function returns the largest item in an iterable or the largest of two or more arguments

Answer 34

**Answer** `max()` **Signature** ``` max(iterable, *, key=None) max(iterable, *, default, key=None) max(arg1, arg2, *args, key=None) ``` **Example** ``` >>> max([1, 5, 3]) 5 >>> max(10, 20, 7) 20 >>> max(["apple", "banana", "pear"]) 'pear' >>> words = ["apple", "banana", "pear"] >>> max(words, key=len) 'banana' >>> numbers = [-4, 1, 7, -10] >>> max(numbers, key=lambda x: abs(x)) -10 ```

Question 35

What built-in Python function returns the smallest item in an iterable, or the smallest of two or more arguments?

Answer 35

**Answer** `min()` **Function Signatures** ``` min(iterable, *, key=None) min(iterable, *, default, key=None) min(arg1, arg2, *args, key=None) ``` **Example** ``` >>> min([3, 1, 4, 2]) 1 >>> min(10, 5, 7) 5 >>> min(["apple", "banana", "pear"], key=len) 'apple' >>> min([], default=0) 0 ```

Question 36

What built-in Python function converts an integer to an octal string?

Answer 36

**Answer** `oct(x)` **Examples** ``` >>> oct(8) '0o10' >>> >>> oct(-56) '-0o70' >>> format(10, 'o') '12' ```

Question 37

What built-in Python function returns an integer representing a Unicode character?

Answer 37

**Answer** `ord(c)` **Example** ``` >>> ord('a') 97 ```

Question 38

What built-in Python function returns a number raised to a power, optionally modulo a third argument?

Answer 38

**Answer** `pow(base, exp, mod=None)` **Examples** ``` >>> pow(2, 4) 16 >>> 2**4 16 ```

Question 39

What built-in Python function creates a range of numbers as a `range` object?

Answer 39

**Answer** `range()` **Signatures** ``` range(stop) range(start, stop, step=1) ``` **Examples** ``` >>> range(5) range(0, 5) >>> list(range(1, 10, 2)) [1, 3, 5, 7, 9] ```

Question 40

What built-in function reverses an sequence

Answer 40

`reversed(seq)` `seq` must implement the `__reversed__()` method

Question 41

What built-in function returns a new set object from an iterable

Answer 41

`set(iterable)`

Question 42

What built-in function returns a slice of an object

Answer 42

`slice(stop)` `slice(start, stop, step=None)` Slice objects are also generated when extend indexing syntax is being used, e.g. `a[start:stop:step]`

Question 43

What built-in function returns a new sorted list from an iterable

Answer 43

`sorted(iterable, /, *, key=None, reverse=False)`

Question 44

What built-in function returns a string version of an object

Answer 44

`str(object='')` `str(object=b'', encoding='utf-8', errors='strict')`

Question 45

What built-in function returns sum of an iterable

Answer 45

`sum(iterable)` `sum(iterable /, start =0)`

Question 46

What built-in function returns a new tuple object from an iterable

Answer 46

`tuple(iterable)`

Question 47

What built-in function is used to iterate over several iterables in parallel

Answer 47

`zip(*iterables, strict=False)` ``` >>> for item in zip([1,2,3], ['a','b','c']): ... print(item) ... (1, 'a') (2, 'b') (3, 'c') ```

Question 48

What are naming conventions for variables and functions

Answer 48

Names should be lowercase separated by underscores (snake case) ``` def add_two_numbers(num_one, num_two): return num_one + num_two ```

Question 49

What are naming conventions for constants

Answer 49

Constants are written in all capital letters with underscores separating words ``` PI = 3.14 MAX_OVERFLOW = 4 TOTAL = 1337 ```

Question 50

How can you simulate a heap

Answer 50

``` from heapq import * heap = [] # add elements to a heap heappush(heap, 2) heappush(heap, 1) heappush(heap, 3) # Check minimum element heap[0] # Pop minimum element heappop(heap) # Get the size of the heap len(heap) # Convert an array to a heap in O(n) nums = [42, 2, 13, 74, 420] heapify(nums) ```

Question 51

How can you count the number of a certain characters in binary, hex, or octal. E.g. Count the number of 1's in `0b101`

Answer 51

``` >>> bin(5) '0b101' >>> bin(5).count('1') 2 >>> hex(54) '0x36' >>> hex(54).count('3') 1 ```

Question 52

What methods are used in string and binary sequence types to determine if the value is a digit, alphabetical, or alphanumeric

Answer 52

`.isdigit()` `.isalpha()` `.isalnum()`

Question 53

What built in module is useful for creating iterators for efficient looping

Answer 53

`itertools` ``` from itertools import * >>> product('ABCD', repeat=2) AA AB AC AD BA BB BC BD CA CB CC CD DA DB DC DD >>> permutations('ABCD', 2) AB AC AD BA BC BD CA CB CD DA DB DC >>> combinations('ABCD', 2) AB AC AD BC BD CD >>> combinations_with_replacement('ABCD', 2) AA AB AC AD BB BC BD CC CD DD ```