Python Flashcards by Zachary Radtka

What are the logical operators in Python

and, or, and not

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What are the bitwise operators in Python

&, |, and ^

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What are the priorities of the sequence operations in Python

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)

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

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

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What sequence operation is used to concatenate two sequences

seq1 + seq2

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What sequence operation is used to repeat a sequence

seq * n or n*seq

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

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

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

len(seq) the length of seq

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

min(seq) the smallest item of seq

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

max(seq) the largest item of seq

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

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

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

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

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What are the basic sequence types in Python

list, tuple, range

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What are Falsey values in Python

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)

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What are Truthy values in Python

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

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

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

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

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

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When designing a hash map what are some good design choices

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

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How can you use a list to simulate a stack

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

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How can you simulate a queue

# 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

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

abs(x)

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

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

bin(x)

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

What built-in function returns the string representing a character whose Unicode code point is the integer i

chr(i)

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

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

divmod(a, b)

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

What built-in function returns an enumerate object

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

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

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

What built-in function returns a new frozenset object

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

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

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

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

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

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

`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 ```

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

`len(s)`

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

`list(iterable)`

What built-in function returns a map object from a function and multiple iterables

`map(function, iterable, *iterables)` If additional iterables arguments are passed, function must take that many arguments and is applied to the items from all iterables in parallel.

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

`max(iterable, *, key=None)` `max(iterable, *, default, key=None)` `max(arg1, arg2, *args, key=None)`

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

`min(iterable, *, key=None)` `min(iterable, *, default, key=None)` `min(arg1, arg2, *args, key=None)`

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

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

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

`ord(c)` ``` >>> ord('a') 97 ```

What built-in function returns the base to the power, e.g. 2^4

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

What built-in function returns a range object

`class range(stop)` `class range(start, stop, step=1)`

What built-in function reverses an sequence

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

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

`set(iterable)`

What built-in function returns a slice of an object

`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]`

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

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

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

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

What built-in function returns sum of an iterable

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

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

`tuple(iterable)`

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

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

What are naming conventions for variables and functions

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

What are naming conventions for constants

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

How can you simulate a heap

``` 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) ```

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`

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

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

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

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

`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 ```