Python - Data Types

Question 1

Research: what is a Data Type in the Python Programming Language.

Answer 1

Data values in Python are known as objects; each object, aka value, has a type.

Question 2

List and Describe: each Data Type in the Python Programming Language.

Answer 2

Numbers
Sequences
Sets
Dictionaries
None
Ellipsis (…)
Callables
Boolean Values

Question 3

What is the ‘numbers’ data types in the Python Programming Language?

Answer 3

The ‘numbers’ data types are built-in numeric types such as integers, floating-point numbers and complex numbers.

Question 4

What is a ‘sequence’ data type in the Python Programming Language?

Answer 4

A sequence is a container of ordered of items, indexed by integers.

Question 5

What is a ‘set’ data type in the Python Programming Language?

Answer 5

A ‘set’ is a container of an arbitrarily ordered collection of unique items that can be of different types.

Question 6

What is a ‘dictionary’ data type in the Python Programming Language?

Answer 6

A ‘dictionary’ is a container of mappings of an arbitrary collection of objects indexed by arbitrary values. An array of key-value pairs.

Question 7

What is the ‘none’ data type in the Python Programming Language?

Answer 7

The ‘none’ data type denotes a null object.

Question 8

Describe ‘callable’ data types in the Python Programming Language?

Answer 8

A ‘callable’ data type supports the function call operation. Examples are function, generators and methods.

Question 9

What is the ‘boolean’ data type in the Python Programming Language?

Answer 9

A ‘boolean’ data type evaluates to either True of False. Any data value in python can be used as a truth value.

Question 10

What are the three built-in types that are numerical data types?

Answer 10

The built-in numeric types in Python include integers, floating-point numbers, and complex numbers.

Question 11

List and Describe: the four Integers literals of the numerical data types.

Answer 11

Decimal
A decimal literal is a sequence of digits in which the first digit is nonzero.

Binary
A binary literal is 0b followed by a sequence of binary digits (0 or 1).

Octal
An octal literal is 0o followed by a sequence of octal digits (0 to 7).

Hexadecimal
hexadecimal literal is 0x followed by a sequence of hexadecimal digits (0 to 9 and A to F, in either upper- or lowercase).

Question 12

Describe: floating-point literals of the numerical data types.

Answer 12

A floating-point literal is a sequence of decimal digits that includes a decimal point (.), an exponent suffix (e or E, optionally followed by + or -, followed by one or more digits), or both.

Question 13

Describe: Complex Number of the numerical data types.

Answer 13

A complex number is made up of two floating-point values, one each for the real and imaginary parts.

You can access the parts of a complex object z as read-only attributes z.real and z.imag.

Examples: 0j, 0.j, 0.0j, .0j, 1j, 1.j, 1.0j, 1e0j, 1.e0j, 1.0e0j

You can specify an imaginary literal as any floating-point or integer decimal literal followed by a j or J. The j at the end of the literal indicates the square root of -1, as commonly used in electrical engineering (some other disciplines use i for this purpose, but Python uses j).

Question 14

Name three types of sequences in the Python Programming Language

Answer 14

Python has built-in sequence types known as strings (bytes or str), tuples, and lists.

Question 15

Research: the term ‘iterate’, ‘iterable’ and ‘iterator’.

Answer 15

An iterable is any Python object capable of returning its members one at a time, permitting it to be iterated over in a for-loop.

Question 16

What is the difference between a bounded iterable and an unbounded iterable in the Python Programming Language?

Answer 16

A bounded iterable is an iterable that eventually stops yielding items.
An unbounded iterable is an iterable that has no limit.

Question 17

What are ‘strings’ in the Python Programming Language?

Answer 17

‘Strings’ are classified a ‘Sequences’.
‘Strings’ are objects that contain either a sequence of characters or a sequence of bytes.

Question 18

Research the term ‘immutable’.

Answer 18

Wikipedia: an immutable object (unchangeable object) is an object whose state cannot be modified after it is created. This is in contrast to a mutable object (changeable object), which can be modified after it is created.

Question 19

Are strings ‘mutable’ or ‘immutable’?

Answer 19

Strings of both types in Python are immutable: when you perform an operation on strings, you always produce a new string object of the same type, rather than mutating an existing string.

Question 20

What is the difference between a single quoted string, a double quoted string and a triple quoted string.

Answer 20

All quoted strings create string literals, but in a triple quoted string, line breaks act as newline characters.

Question 21

What are ‘raw string literals’ in the Python Programming Language?

Answer 21

‘Raw string literals’ do not evaluate escape sequences. They are quoted and triple quoted strings preceded with an ‘r’ or ‘R’.

Question 22

What are ‘formatted string literals’?

Answer 22

Formatted string literals (commonly called f-strings) let you inject formatted expressions into your string “literals

Question 23

How do you concatenate multiple string literals into one?

Answer 23

Use parentheses:

marypop = (‘supercali’ # ‘(‘ begins logical line,
‘fragilistic’ # indentation is ignored
‘expialidocious’) # until closing ‘)’

Question 24

What is a ‘bytes’ object?

Answer 24

A bytes object is an immutable ordered sequence of ints from 0 to 255.

Question 25

How do you create a ‘bytes string literal’?

Answer 25

A bytes literal has the same syntax as a str literal, prefixed with ‘b’: b’abc’

Also: bytes([97, 98, 99])

Also a ‘raw byte literal’: rb’\ = solidus’

Question 26

What is a ‘bytearray’?

Answer 26

A bytearray is a mutable ordered sequence of ints from 0 to 255:
ba = bytearray([97, 98, 99])
ba[1] = 97
print(ba.decode())

Question 27

What is the sequence called ‘tuple’?

Answer 27

A tuple is an immutable ordered sequence of items. The items of a tuple are arbitrary objects and may be of different types.

Question 28

What are four ways of creating a tuple?

Answer 28

tuple: 100, 200, 300 # Tuple with three items
one-item tuple: (3.14,) # Tuple with one item, needs trailing comma
empty tuple: ()
tuple built-in type: tuple(‘wow’) #creates (‘w’, ‘o’, ‘w’)

Question 29

What is the sequence called ‘list’?

Answer 29

A list is a mutable ordered sequence of items. The items of a list are arbitrary objects and may be of different types

Question 30

What are four ways of creating a list?

Answer 30

[42, 3.14, ‘hello’] # List with three items
[100] # List with one item
[] # Empty list
list(‘wow’) #creates [‘w’, ‘o’, ‘w’]

Question 31

What is a hash table and what does it mean to be hashable?

Answer 31

An object is hashable if it has a hash value that never changes during its lifetime.

Question 32

What are the two types of built-in Sets and what is the difference?

Answer 32

‘set’ is mutable and ‘frozenset’ is immutable.

Question 33

What are the two ways to create a set?

Answer 33

To denote a (nonfrozen, nonempty) set, use a series of expressions (the items of the set) separated by commas (,) within braces ({}):
{42, 3.14, ‘hello’}

or use the built-in type: set()

Question 34

What are the three ways to create a dictionary?

Answer 34

{1:’za’, ‘br’:23} # Dictionary with different key types
{} # Empty dictionary
dict(x=42, y=3.14, z=7) #built-in type
dict([(1,’za’), (‘br’,23)]

Question 35

What code is used to unpack a ‘dict’ into another ‘dict’?

Answer 35

unpack a dict’s contents into another dict using the ** operator

d1 = {‘a’:1, ‘x’: 0}
d2 = {‘c’: 2, ‘x’: 5}
d3 = {**d1, **d2}

or use the | operator (python 3.9+)

d4 = d1 | d2

Question 36

How do you create a dictionary using the ‘dict.fromkeys’ method?

Answer 36

The first argument is an iterable whose items become the keys of the dictionary; the second argument is the value that corresponds to each and every key (all keys initially map to the same value). If you omit the second argument, it defaults to None.

dict.fromkeys(‘hello’, 2) # Same as {‘h’:2, ‘e’:2, ‘l’:2, ‘o’:2}
dict.fromkeys([1, 2, 3]) # Same as {1:None, 2:None, 3:None}

Question 37

What does the ellipsis (‘…’) mean in python?

Answer 37

an indicator of “no value supplied, not even None.” Ellipsis is hashable and so can be used as a dict key

Question 38

How are data values used to indicate True or False?

Answer 38

Any nonzero number or nonempty container (e.g., string, tuple, list, set, or dictionary) is true.

Zero (0, of any numeric type), None, and empty containers are false.