Python Fundamentals

Question 1

GENERAL

Answer 1

GENERAL

Question 2

How does logical operators work?

Answer 2

There are two main logical operators ‘and’ & ‘or’ which operate
on boolean values. The ‘and’ operator needs both values to be
True to return a True result. The ‘or’ operator only needs
one value to be True to return a True result.

Question 3

What is boolean logic?

Answer 3

Boolean logic is the name given to comparison operations whose
result is True or False.
==
!=
>
<
>=
<=
are all comparison operations that result in True or False

Question 4

Is it possible to assign a maximum or minimum value to a variable in python.

Answer 4

Yes, python has the concept of positive and negative infinity which is a float.

Question 5

What is a bitwise operation?

Answer 5

A bitwise operation is a logical operation performed on individual bits where 0 represents false and 1 represents true.

A bitwise ‘&’ operation tends to drop bits

A bitwise ‘|’ operation tends to add the bit together

Question 6

What is binary? how does it work?

Answer 6

The binary number system is the base two representation of numbers using only two symbols 0 and 1.
When writing a number in binary, the prefix 0b is used to indicate that what follows is a binary number.

0b0101 is 5

Question 7

What is floor division and what is the result of performing this operation?

Answer 7

floor division is just like regular division except the result is always an integer i.e. the decimal portion of the result is dropped NOT rounded.

Question 8

What are the main types in python?

Answer 8

string, integer, float, boolean and None

Question 9

How do we assign a multi-line string?

Answer 9

By using “”” (triple quotes)

Question 10

Is there an increment and decrement operator in python?

Answer 10

Yes it is the ‘+= ‘ and ‘-=’.
‘++’ and ‘- -‘ do not exist in python like many C-style programming languages.

Question 11

Is type hinting enforced by python?

Answer 11

The python interepter does not enforce types. Python is dynamically typed therefore type hinting only allows the user of the code to see the expected types.

Question 12

Is python statically or dynamically typed?
What does this mean?

Answer 12

python is dynamically typed, which means you can assign any type to a variable, more IMPORTANT this also means that you can change the type of the variable after its assignment.
This in NOT recommended however.

Question 13

DATE
<===>

Answer 13

DATE
<===>

Question 14

syntax for creating a date object?

Answer 14

Use single integer inputs when creating the date object.

Question 15

CONTROL FLOW
<===========>

Answer 15

CONTROL FLOW
<===========>

Question 16

Short hand syntax for if-statement?

Answer 16

(do something) if (condition) else (do something else)

Question 17

for-else….?

Answer 17

The else statement can be used with a loop as folows:

Question 18

FUNCTONS
<===========>

Answer 18

FUNCTONS
<===========>

Question 19

what is a function and what keyword is used to create one?

Answer 19

A function is a reusable block of code, that returns a result or performs an action. The ‘def’ keyword is used to declair a function.

Question 20

Function parameters vs arguments

Answer 20

The function parameters are the inputs to the function at its definition, the arguments on the other hand are the inputs used when calling the function.

Question 21

Can you call a function before it ‘s declaration?

Answer 21

You cannot call a function before you declare it. A common convention in many languages is to use a single main function which is then called at the end as the entry point for the program, this ensures all subsequent functions are called in the correct order.

Question 22

What value is returned by a function without a return keyword or the return keyword without a value?

Answer 22

None

Question 23

Can a Python function return multiple values?

Answer 23

Yes. A return statement followed by a list of comma seperated values will return each value. When the function is called an equal number of variables must be used in the order they were returned.

Question 24

What are the three types of arguments we can pass to a function?

Answer 24

Positional arguments, Keyword arguments, and Default arguments

Question 25

What are positional arguments?

Answer 25

A positional arguments is an arguments that can be called by their position in the function definition.

positional call to function:

calculate_taxi_price(100, 10, 5)

Question 26

What are Keyword arguments?

Answer 26

Arguments that can be called by their name.

keyword argument call to function:

calculate_taxi_price(rate=0.5, discount=10, miles_to_travel=100)

Question 27

What are default arguments?

Answer 27

Arguments that are given default values in the function definition.

def calculate_taxi_price(miles_to_travel, rate, discount = 10):
  print(miles_to_travel * rate - discount )

When using a default argument, we can either choose to call the function without providing a value for a discount (and thus our function will use the default value assigned) or overwrite the default argument by providing our own.

Question 28

How would you create a function that accepts unlimited arguments?

Answer 28

Note that to assing a value to the age argument you must use key-word assignment syntax (age=10) or position age as the first argument in the sequence.

Question 29

Accept unlimited keyword arguments?

Answer 29

Note kwargs is just a convention and not a keyword.

Question 30

Unlimited args and kwargs

Answer 30

args:tuple kwargs:dict

Question 31

Positional args only?

Answer 31

Question 32

Kwargs only?

Answer 32

Question 33

Combination args?

Answer 33

Question 34

LOOPS
<======>

Answer 34

LOOPS
<======>

Question 35

What is a loop? how do you construct a for loop?

Answer 35

A loop allows us to perform an action multiple times without explicitly writing it each time.

Note: In the sample code 0-9 will be printed.

Question 36

How does the range() function work?

Answer 36

The range function takes a single input and returns a range object. The range object can be converted into a list by using the list() function.

Question 37

How does the range() function work in a for loop?

Answer 37

The range function when used with a for loop generally uses two parameters a start value and end value which is exclusive. An optional third argument can be used the ‘step’ which determines how much to add to ‘i’ in each iteration of the loop. using a negative value for the step input will cause the iteration to go backwards.

Question 38

What is a While-loop?
What is the syntax?

Answer 38

A while loop performs a given set of instructions as long as a given condition is true.

while True:
  do something

Note: The condition must eventully evaluate to false to exit the loop.

Question 39

How does the ‘break’ and ‘continue’ keywords affect the processing of a loop?

Answer 39

When the python interpreter hits the ‘break’ statement it will exit the loop.
In the case of the ‘continue’ keyword the interpreter will skip to the next iteration cycle.

Question 40

LIST
<====>

Answer 40

LIST
<====>

Question 41

What is a list and how do you create one?

Answer 41

A list is a simple data structure that can store items of any data type. Lists also know as an array stores and references items by index. The index start at zero and indicates the items position in the list:

Question 42

How do you find the number of items in a list?

Answer 42

Pass the list as an argument to the ‘len()’ function

Question 43

Can items in a list at a specific index be mutated?

Answer 43

Yes. simply assign the new value directly to the desired index. Note that this will replace any value currently at that index.

Question 44

What does the ‘append()’ method do when used with a list?

Answer 44

The append method adds the given argument to the end of the list.

Question 45

What does the ‘.pop()’ method do when used with a list?

Answer 45

The pop method removes the last item in the list and returns it. It can also take an optional argument which is the index of the element you wish to remove.
my_list.pop(2)

Question 46

How does the .insert method work when used on a list?

Answer 46

The ‘.insert’ method is called on the list, it expects a minimum of two inputs the index for insertion and the element to be inserted.

Question 47

When accessing a list

alternative to the ‘indexed for-loop’?
when should you use it?

Answer 47

If you do not need to update the item(s) in a list i.e. you only need to access the item and not its index you can use the ‘for-in’ syntax

Question 48

Using slice syntax “return a slice of the list from index 1, up to but not including 5, skipping every 2nd value.

Answer 48

Note that slicing returns a new list.

Question 49

How do we concatenate lists together?

Answer 49

Simply use the ‘+’ operator.

you can also use the += operator or call the extend() method on a list.

Question 50

How to check for an item in a list without using a ‘if-statement’?

Answer 50

By using the ‘in’ keyword. This will return a Boolean value.

Question 51

How do we delete specific items from a list?

Answer 51

Use the ‘del’ keyword followed by the name of the list square brackets containing the index or slices you wish to delete.
The ‘.pop()’ method with a index as an argument can also be used.

Question 52

How to remove an item from a list by name not index?

Answer 52

Use the remove() method with the item as the argument.

Question 53

How does the ‘.count()’ method work?

Answer 53

The ‘.count()’ method will count the number of times an element appears in a list.

Question 54

How does the ‘.sort()’ method work?

Answer 54

The ‘.sort()’ method will sort a list alphabetically or numerically.
Calling the method on a list with no inputs sorts the list in ascending order.
my_list.sort()

To sort in descending order pass the following argument to the method.
my_list.sort(reverse=true)

Note that the ‘.sort()’ method modifies the original list and does not return any value.

Question 55

What is the difference between the ‘.sort()’ method and ‘sorted()’ function?

Answer 55

The main difference is that the sorted() function does not modify the original list like the .sort() method does. Therefore using the sorted() function will return a value that can be stored in a variable for use.

names = [“Xander”, “Buffy”, “Angel”, “Willow”, “Giles”]
sorted_names = sorted(names)
print(sorted_names)

Question 56

How do we easily access the last element in a list

Answer 56

use negative indexing
my_list[-1]

Question 57

How do we append multiple items to a list?

Answer 57

use ‘+’ to concatenate two lists together: Note that the original list was not modified, only lists can be concatenated this way.

Question 58

What is a list comprehension?

Answer 58

A list comprehension is a concise way to create lists in Python. It provides a compact syntax for generating a new list by iterating over an existing iterable (such as a list, tuple, set, or even a string), applying an expression to each element, and optionally including only certain elements based on a condition.

Question 59

Basic list comprehension syntax

Answer 59

output: [2, -2, 158, 66, -90]

Question 60

list comprehension with condition and expression syntax

Answer 60

The syntax for the list comprehension changes based on conditional statement and it’s complexity.

Question 61

STRING OPERATIONS
<================>

Answer 61

STRING OPERATIONS
<================>

Question 62

How does the ‘+’ operator work when used with strings?

Answer 62

The ‘+’ operator will concatenate two or more strings into a single string.

Question 63

How does the replace() method work?

Answer 63

this method takes two arguments, it then replaces all instances of the first argument with the second argument. Note this is a substring method.

Question 64

How does the find() method work?

Answer 64

This method takes a string as an argument it then searches the string it was called on and returns the first index value where that substring is located.

Question 65

How does the .format() method work?

Answer 65

This method can be used to interpolate variables into a string. Use a ‘f-string’ instead!

Question 66

How does the basic split() method with no argumets work?

Answer 66

The split() method returns a list of substrings that has been split by a delimiter. If no argument is passed to the method the default delimiter is the “ “ space character.

Question 67

How does the split method work with a delimiter as an argument?

Answer 67

Note that the delimiter must be passed as a string. The delimiter is not included in the list of substrings, the method returns a empty string if the string ends with the delimiter.

print(greatest_guitarist.split(‘a’))
output: [’s’, ‘nt’, ‘n’, ‘’”]

Note you can also split based on escape characters such as \n “newline” and \t “horizontal tab”

Question 68

How does the join() method work?

Answer 68

The join() method is the opposite of the split() method. It uses a delimiter to join a list of strings.

‘delimiter’.join(list_you_want_to_join)

Question 69

How do we create a csv from a list?

Answer 69

CSV stands for “Comma-Separated Values.” It is a simple and widely used file format for storing tabular data, such as spreadsheets or databases.

call the join() method on a “ ,” with a list of strings as the argument.

”,”.join(my_list_of_strings)

Question 70

How does the strip() method work?

Answer 70

The strip() method with no arguments when called on a string removes white space from the start and end of the string. The method can also be called with a specific character which will be stripped from the start and end of the string.

Question 71

Strings are immutable, what does this mean?

Answer 71

This means a string once created cannot be changed. Operations performed on strings such as slicing and concatenation create a new string.

Question 72

What are the three main string methods that can change the case of a string?

Answer 72

‘.lower()’
‘.upper()’
‘.title()’
remember that strings are immutable so the result is a new string. The original string does not change.

Question 73

TUPLES
<======>

Answer 73

TUPLES
<======>

Question 74

What is a tuple?

Answer 74

A tuple is a data structure similar to a list but whos data is immutable.
To create a tuple use the rounded brackets.
To create a single item tuple you must use a trailing comma:
my_tuple =(4,)
You can also unpack a tuple by using multiple variables
name, age, occupation = (“murphy”, 39, “Data Engineer”)

Question 75

How is the ‘zip()’ function used?

Answer 75

The ‘zip()’ function is used to combine two or more iterables (such as lists, tuples, or strings) into a list of tuples paired based on their position.
Note that the zip() function will create an iterator you will need a loop to access the items.

Question 76

MODULES
<========>

Answer 76

MODULES
<========>

Question 77

What is a python module?

Answer 77

A module is a collection of python declarations intended to be used as a tool. The basic syntax is.

from module_name import object_name

> from datetime import datetime

You can also select the whole module for use:
import random

> random.choice(my_list)

Question 78

Explain module namespacing

Answer 78

A namespace isolates the function, classes and variables defined in the module from the code in the file doing the callng.
The name of the module is the name given to the namespace by default. This can be changed however using aliasing.

import module_name as name_you_pick_for_the_module

Question 79

if __name__ == ‘__main__’ ?

Answer 79

‘__main__’ refers to the current module being executed. so the calls will not be executed unless it was called locally.

Question 80

Virtual Environments
<================>

Answer 80

Virtual Environments
<================>

Question 81

Python virtual Environments

Answer 81

Python virtual environments allows you to manage the dependencies for a project in separate environments. Packages are installed at the project level not globally. pipenv is one package used to create and manage these environments.

Question 82

How do we create a virtual environment with pipenv?

Answer 82

Make sure the pipenv module is installed. navigate to the root of the project directory and execute the command:
$ pipenv –three
this will initialize the virtual enviroment.
Note a ‘pipfile’ will be created in the directory that contains all the info about the virtual environment and the project dependencies.

Question 83

How do we install packages with pipenv?

Answer 83

Make sure your in the desired project directory, use the command:
$ pipenv install package_name

to specify a version of a package use:
$ pipenv install package_name ==2.18.1

Note that using the command:
$ pipenv shell
will allow you use the shell within that virtual environment with all it’s specific dependencies.

Question 84

DICTIONARY
<===========>

Answer 84

DICTIONARY
<===========>

Question 85

What is a dictionary?

Answer 85

A dictionary is a data structure that is used to stores a collection of items using key, value pairs. Unlike lists which are indexed by position, dictionaries are indexed by keys. Keys must be unique, must be ‘hashable’ type so therefore a list or dictionary cannot be used as a key, hashable values are values that will not change such as numbers and strings.

Question 86

How do we access the values in a dictionary?

Answer 86

by using the key in square brackets similar to accessing the index of a list.

Question 87

What is the syntax for adding key/value pairs to an existing dictionary?

Answer 87

using the square bracket syntax use the assignment operator to give that key a value.

Question 88

What happens in a dictionary when value is assigned to a key that already exists?

Answer 88

The value is overwritten. Each key in a dictionary must be unique.

Question 89

How can we check if a key is present in a dictionary?

Answer 89

Simply use the ‘in’ keyword, this will return a Boolean value.

Question 90

What is the syntax for iterating over a dictionary?

Answer 90

Use a for-in loop. Note that the value held in the loop variable is a ‘key’.

Question 91

What happens when you try to access a key that does not exist?

Answer 91

a ‘keyError’ is thrown

Question 92

How does the update() method work?

Answer 92

The update() method allows us to add multiple key value pairs to a dictionary at the same time.

Question 93

How do we delete a key from a dictionary?

Answer 93

Use the ‘del’ keyword along with the square bracket syntax and the key you wish to delete.

Question 94

How does the .get() method work with a dictionary?

Answer 94

The .get() method will return the value if it exists, otherwise it will return none, or the value used as the optional second argument for the method.

You can also use my_dict.setdefault(‘xx’, ‘key does not exist’) method to get similar behaviour as the .get method.

Question 95

How to remove an item from a dictionary with the .pop() method?

Answer 95

Note that using the .pop() method on a dictionary requires at least one argument, i.e. the key to be removed, an optional second argument can be used which will be the value to return if the key does not exist in the dictionary. Remeber that the .pop() method removes the item but also returns the value for use.
EXAMPLE:

raffle = {
223842: “Teddy Bear”,
872921: “Concert Tickets”,
320291: “Gift Basket”,
412123: “Necklace”,
298787: “Pasta Maker”
}

Question 96

What is the result of passing a dictionary as an argument to the list function:
list(my_dict) ?

Answer 96

This will return a list of all the keys in the dictionary.
EXAMPLE
test_scores = {
“Grace”: [80, 72, 90],
“Jeffrey”: [88, 68, 81],
“Sylvia”: [80, 82, 84],
“Pedro”: [98, 96, 95],
“Martin”: [78, 80, 78],
“Dina”: [64, 60, 75]
}

Question 97

How does the .keys() method work when called on a dictionary?

Answer 97

The .keys() method returns a dict_keys object that contains all the keys in the dictionary, the dict_keys object is a view only object items cannot be removed or added however, It can be iterated.

Question 98

How to get all the values in a dictionary?

Answer 98

Use the .values() method. It will return a dict_values object that can be iterated.

Question 99

Using a for-loop and the .items() method, how do we get all the keys and values from a dictionary?

Answer 99

Using the .items() method returns a dict_list object which is a tuple in a (key, value) format which can be used in a loop as follows:

Question 100

Syntax for creating a dict comprehension?

Answer 100

Question 101

Files
<==>

Answer 101

Files
<==>

Question 102

What is the syntax for opening a file?

Answer 102

with open('welcome.txt') as text_file:
    text_data = text_file.read()
    print(text_data)

Note that read() returns the file as one single string.
Also text_file is a file object that we then use to perform various actions.

Question 103

How does the readlines() function work?

Answer 103

It reads the text file line by line.

with open('how_many_lines.txt') as lines_doc:
  print(lines_doc)
  for line in lines_doc.readlines():
   print(line)

Note that readlines() returns a list with each line in the file.

Question 104

How would we access only a single line in a file?

Answer 104

By calling the readline() method on the
file object.

with open('millay_sonnet.txt') as sonnet_doc:
  first_line = sonnet_doc.readline()
  second_line = sonnet_doc.readline()
  print(second_line)

Question 105

What is the syntax for writing a file?

Answer 105

To write a file we use the open() function with a second argument ‘w’ for write mode.If the file already exists it will be over-written.

Note that the open() function uses ‘r’ by default as the second argument, so it is optional when reading a file.

Question 106

Appending to an existing file?

Answer 106

If you do not want to overwrite the file you will need to use append mode.

Question 107

Removing a file

Answer 107

import os
if os.path.exists('my_file.txt'):
    os.remove('my_file.txt')

check if the file exists before carrying out an operation on the file.

Question 108

How to remove a folder and all the files in it?

Answer 108

import os

folder_name = 'sample_folder/'
for file in os.listdir(folder_name):
    if os.path.exists(folder_name + file):
		    os.remove(folder_name + file)
os.rmdir('sample_folder')

Question 109

what’s with ‘with’?

Answer 109

The ‘with’ keyword invokes a context manager for the file we’re calling open() on. The context manager takes care of opening the file when we call open() and closing the file when we leave the indent block. We can use the older method of opening and closing a file however this is not recommended since it will cause performance issues if it is not done correctly.

Question 110

working with csv

Answer 110

To work with a csv file the best approach is to use the csv module.

Question 111

CSVs with different delimiters?

Answer 111

Although csv means comma seperated values other delimeters are also valid.

Question 112

Writing a csv file programmatically?

Answer 112

note that the order of the fileds does not need to match the source data.

Question 113

Reading a JSON file?

Answer 113

The json module is used to process json files

note that the result of passing the file object to json.load() is a regular python dictionary and therefore we are able to perform regular dict. operations on the result.

Question 114

Writing a JSON file?

Answer 114

note turn_to_json is the data we wish to convert to json which will be written in the file outout.json

Question 115

What are the different modes available to open a file.

Answer 115

‘r’ - read the default mode
‘w’ - write mode will overwrite if the file already exist
‘a’ - append mode file alteady exist
‘a+’ - append, read and write mode.
‘x’ - make sure the file does not already exist.

Question 116

What is a glob?

Answer 116

The ‘glob’ module is a built-in module used to find all the pathnames matching a spefic pattern according to the rules used by the Unix shell.

Note that the return type is a list.

Question 117

What is pickling?

Answer 117

Pickling is the process used by python to serialize and deserialize objects. The pickle module is used to achieve this.

Note that pickling is not secure and should only be used with trusted sources!

Question 118

Serializing objects with the pickle module?

Answer 118

Question 119

Deserializing objects with the pickle module?

Answer 119

Question 120

Classes
<====>

Answer 120

Classes
<====>

Question 121

What is a class?

Answer 121

A class is a template for a data type. It describes what kind of information the class will hold and how to interact with the data.
We use the ‘class’ keyword to define a class.

Question 122

Instantiation?

Answer 122

For a class to be useful we must create an instance of it.
myinstance = MyClass()

A class instance is also called an object.

Question 123

Class variable?

Answer 123

A class variable or attribute allows every instance of the class to have access to the same varible.

Question 124

Methods?

Answer 124

A method is a function defined as part of a class. The first argument in a method is always the object calling the method.By convention the is usually called ‘self’.

Question 125

Constructor?

Answer 125

There are several special methods that can be defined in classes, they are sometimes referred to as magic or dunnder methods. You can identify them by the double underscore.
A constructor is a special method used to ‘set up an object when it is instantiated.

_ init() _

Question 126

What is a instance variable?

Answer 126

Even though a class is the blueprint for an object. When an object is created it can maintain seperate data from another object created from the same class, this in essence is the instance variable, the opposite of a class variable.

Question 127

Attribute function?

Answer 127

The attribute function can be used to check if an item has a certain attribute.

Question 128

dir()

Answer 128

Passing any object to the dir() method will return all it’s attributes and methods.

dir(my_function)

Question 129

__repr__(self)

Answer 129

The __repr__() dunder method when defined in a class will tell python what the string representation of the class should be when we print out an object of that class. The method only takes self as an argument and has to return a string. If __repr__() is not used only the class name and memory address of the object will be printed.

Question 130

What is an enumeration?

Answer 130

An enum is a custom defined type that allows multiple constants to be assigned simultaneously.

Question 131

ERROR HANDLING
<==============>

Answer 131

ERROR HANDLING
<==============>

Question 132

Syntax for handling errors?

Answer 132

Question 133

Raising exceptions?

Answer 133