PCAP

Question 1

State the differences between a compiled language and an interpreted language.

Answer 1

Compiled language:

After compilation, the program can be freely distributed without the need of the interpreter. You must have a compiler for each type of system. Faster execution. Examples: C, C++, Go.

Interpreted language:

The translation is done each time the program runs. The interpreter must be installed in all the computers to make the code run. Slower execution. Examples: PHP, Ruby, Python, Java.

Question 2

How do you use binary, hexadecimal and scientific notation in Python?

Answer 2

Binary: 0bnnnnnnn

Hexadecimal: 0xnnnnnnn

Scientific notation: nEn, example: 3E8

Large numbers: use underscores (_) to separate big chunks of numbers

Question 3

What are the three different ways you can specify a range in Python?

Answer 3

1. range(2,8,3): range(start, end, increment). The end does not touch

Question 4

List two ways in which you can slice a sequence in Python:

Answer 4

1. Slice function: (,)
   
   • Returns a slice object similar to a range function.
   • You must specify the start, end and step.
     
     • lista = [i for i in range(10)]
     • x = slice(start=None, end, step=None)
     • sliced = lista[x]
2. Bracket slicing - Index Operator: (:)
   
   • lista = [i for i in range(10)]
   • x = lista [start : end : step]

Question 5

Calculate the module of the following operations:

1. 4 % 6 =
2. 2.33 % 2.1 =
3. 10 % 3 =

Answer 5

RAr(AbArAb)

Question 6

What are the different tuple methods?

Answer 6

Leia Meditated Meanwhile Surfers Inhaled Clever Irishmen.

len, min, max, slice, in, count, index

Question 7

List two ways in which you can declare a tuple.

Answer 7

1. Parenthesis:
   
   • my_tuple = (1, )
   • (s1, s2) = (1, 2)
2. No parenthesis:
   
   • my_tuple = 1, 2, 3
   • s1, s2 = 1, 2

Question 8

random Module most used functions and methods:

Answer 8

Strong Robocop Romanced Round Croutons Slowly

Seed, Random, Randrange, Randint, Choice, Sample

Question 9

Useful methods of the datetime.date class:

Answer 9

• .weekday():0 : Monday
• .isoweekday(): 1: Monday (ISO)
• .isoformat(): string : YYYY-MM-DD
• .replace(): replaces the specified parameters.
• .strftime(): readable string format.

Question 10

Useful methods of the datetime.datetime class:

Answer 10

• .today(), .now()

​

• .strftime()
• .strptime()

​

• .fromisoformat(): returns a datetime coming from a string in ISO format
• .isoformat()

​

• .combine(): combines a date and a time
• .replace()

Question 11

Enlist all the different formatting styles that can be used with strftime:

Answer 11

Question 12

Useful methods of the Calendar.Calendar class:

Answer 12

Generators:

• .itermonthdates(year, month): datetime objects.
• .itermonthdays(year, month): int (day#).
• .itermonthdays2(year, month): tuple (day#, weekday#)
• .itermonthdays3(year, month): tuple (year#, month#, day#)
• .itermonthdays4(year, month): tuple (year#, month#, day#, weekday#)

Lists:

• monthdatescalendar(year, month): datetime (separated in weeks).
• monthdayscalendar(year,month): int (day#) (separated in weeks).
• monthdays2calendar(year,month): tuple (day#, weekday#) (separated in weeks).

Question 13

What is a Python generator?

Answer 13

• collections
  
  • ⇒ Iterator()
    
    • ⇒ Generator (yield, list-like)
    • ⇒ [], (), {}, set()
    • ⇒ str(), b””, bytearray(), range(), map()
• Generator:
  
  • yield statement:

def gen():

x = 0

for x in range(10):

if x%2 :

yield x

• list-like:

it = (x for x in range(10) if x % 2)

(PARENTHESIS)

Question 14

tkinter

How do you create the root window in an OOP program?

Answer 14

1. root = tkinter.Tk()
2. app = Application(root)
3. App: def \_\_init\_\_(Frame):
   
   • super().\_\_init\_\_()
   • self.main = tkinter.Frame
4. Pack self.main and this will be the master of all widgets.

Question 15

tkinter

What is the process to create a RadioButton?

Answer 15

1. Create a variable: tkinter.BooleanVar, DoubleVar, IntVar, StringVar.

2. Set a default value for it.
3. Create the radiobutton:
   
   • r1 = tkinter.RadioButton(master, variable =, value=,...)
4. Define the function that sets the tkinter variable.

Question 16

tkinter:

What is the process for creating a Calendar?

Answer 16

1. pip install tkcalendar
2. import tkcalendar.
3. tcal = tkcalendar.Calendar(master, )
4. date_temp = tcal.get_date():String

Question 17

tkinter:

What is the process to create image widgets?

Answer 17

1. pip install Pillow
2. Imports:
   
   • import PIL
   • from PIL import ImageTk, Image
3. Create image object:
   
   • ima = ImageTk.PhotoImage(Image.open("whatever.jpg"))
   • ima = ImageTk.BitmapImage(Image.open("whatever.bmp"))
4. Use the image:
   
   • ​lbl = tkinter.Label(master, image=ima)

Question 18

What is the process to use gspread?

Answer 18

1. Google Cloud Console:
   
   1. https://console.cloud.google.com/
   2. API’s and services.
   3. Create Credentials ⇒ Create a service account (Key type = JSON).
   4. Share the Google Sheet with the client’s email.
2. Code:
   
   1. pip:
      
      • pip install oauth2client
   2. imports:
      
      • import gspread
      • from oauth2client.service_account import ServiceAccountCredentials
   3. Create creds:
      
      • creds = ServiceAccountCredentials.from_json_keyfile_name("")
      • client = gspread.authorize(creds)
   4. Open a worksheet:
      
      • sheet = client.open("name")
      • worksheet1 = sheet.worksheet("name")
   5. ​Using gspread:
      
      1. Get a value:
         
         1. val = ws.cell(1,2)
         2. vals = ws.row_values(2)
      2. Update a value:
         
         1. ws.update_cell(1,2, "hello")
         2. ws.update("A1:B1", [[1, 2],[3, 4]])

Question 19

What is the meaning of API?

Answer 19

Application Programming Interface

Question 20

What are the basic principles of a REST API?

Answer 20

REpresentational State Transfer.

It has 6 constraints (LUCCCS):

1. Layered:
   
   • Intermediate dedicated servers(security, load balancing), client does not know to which server it’s communicating.
2. Uniform Interface:
   
   1. Resource Based:
      
      • Server sends a representation of resources. Uniquely identified resource.
   2. Self-descriptive Messages:
      • Each message contains everything needed.
   3. Hypermedia (HATEOAS):
      
      • Body, request - response headers, URIS.
3. Cacheable:
   
   • The client caches info to decrease client-server interactions. Improves client performance.
4. Client server architecture:
   
   • Server: data storage. Client: UI. HTTP requests, client portability, client-server independence.
5. Code on demand (optional)
   
   • Server returns code to the client (Javascript, Java applets).
6. Statelessness:
   
   • Each client request should have the creds, so no session keeps open by the server.

Question 21

What does OAuth stand for?

Answer 21

Open Authorization

(HTTP requests)

Question 22

What types of OAuth grants exist?

Answer 22

1. Resource owner password credentials:
   
   • Resource owner supplies creds.
   • Unsafe.
2. Client credentials:
   
   • Resources are owned by the client itself.
3. Authorization code:
   
   • Most commonly used.
   • Auth server issues an auth code, then access token - refresh token.
   • Resource owner credentials, never shared.
4. Implicit:
   
   • No Oauth code is issued, only access tokens.

Question 23

How do you use map()?

Answer 23

• Transform a set of items without the need for iteration in one single expression:
• map_object = map (callable, iterable)
• Callable (function):
  
  • Class constructors: Class()
  • User defined function.
  • Built-in function.
  • lambda functions.
• Example:
  
  • mapa = map(lambda x,y: x-y, [5,5,5],[1,3,5])
  • >> 4 2 0

Question 24

How do you use a lambda function? What are they useful for?

Answer 24

• lambda arguments(n, *): expression(just 1, no statements)
• Wherever a regular function object is allowed (lambda: syntactic sugar, anonymous function).
• Functional paradigm, often used with map(), filter(), reduce().

Question 25

What is a **_JSON_** file?

Answer 25

**JavaScript Object Notation**

Question 26

What is the basic process for a `pickle` file?

Answer 26

* Python specific. * Read: `with open("file.pickle", "rb") as file:` `data = pickle.load(file)` * Write: `with open("file.pickle", "wb") as file:` `pickle.dump(any_object, file)`

Question 27

What are the most used types of **_HTTP request methods_**?

Answer 27

* **GET:** request data. * /test/demo\_form.php?name1=value1&name2=value2 * **POST:** send data to a server * data sent is stored in the request body of the HTTP request * **HEAD:** response identical to that of a GET request, but without the response body. * **DELETE** /file.html HTTP/1.1

Question 28

What are the basic **_elements of an API_**?

Answer 28

* Most of the time, API means REST API.

Question 29

What does **_GIT_** stand for?

Answer 29

**Global Information Tracker**

Question 30

What are other types of **_version control systems_**?

Answer 30

* **Azure DevOps:** * Team Foundation Version Control (TFVC) or Git * Entire application lifecycle: * Reporting. * Requirements management. * Project management (for both agile software development and waterfall teams) * Automated builds * Testing * Release management. * **Apache Subversion:** * Versioning and revision control system distributed as open source. * **Perforce:** * Software used for developing and running applications, including version control software, web-based repository management, developer collaboration, application lifecycle management, web application servers, debugging tools and Agile planning software (DevOps). * **Mercurial:** * Free, distributed source control management tool. * Mainly Python. * $ hg clone "URL", $ hg add (new files)

Question 31

What is the basic process for creating a **_GIT repo_**?

Answer 31

* **Download** GIT. * git-scm.com * **Init** repo: `$ git init` * Create a **.gitgnore** file. * First Time config: `$ git config --global user.name "name"` `$ git config --global user.email "something@mail.com"` * **_Commit_**: `$ git add filename.txt, $ git add .` `$ git commit -m "description"` `$ git status` `$ git log`

Question 32

What is a **_git branch_**?

Answer 32

* `$ git branch testing` * **Diverge from the main line**. * Default branch name:`master`(`git init` creates it) * **_HEAD_**: Pointer to current branch * **Commit object:** * Pointer to **snapshot**, * **Author**’s name and email address, * **Message**, * Pointers to parent or **parents**: * Initial commit: 0. * Normal commit: 1 * Merge of two or more branches: Multiple parents. * **Switch to branch:** * `$ git checkout testing` * **Create and switch:** * `$ git switch -c new-branch.` `-c, --create` * `$ git log` **and branches**: * Commit history for branch:` $ git log branch_name` * All branches: `$ git log --all`

Question 33

How do you return to a **_specific snapshot of a GIT repo_**?

Answer 33

* `$ git checkout 40fd555 ` * `$ git checkout branch_name`

Question 34

What is the **_HEAD_** in a GIT repo?

Answer 34

* **_HEAD_**: Pointer to current branch.

Question 35

How do you **_set up a remote repo_**?

Answer 35

* Create a GitHub account. * Create a new repository. * In the **Local** repo: `$ git remote add origin https://github.com/oarpavon99/whatever.git` * **Local** ⇒ **Remote**: `$ git push -u origin master` `$ git push -u(save changes) origin(where?) master(branch)`

Question 36

What are the different **_types of tags_** that you can include in a GIT version?

Answer 36

* `$ git tag` * * `-l:` ***list tags** that match a pattern* `-l "v1.8.5*"` * `-lw`: ***lightweight** tag* (≈ branch) * `-d`: ***delete** tag*`-d v1.4` * **Annotated:** * * `$ git tag -a v1.4 -m "my version 1.4"` * `​$ git tag -a v1.2 9fceb02(checksum)` (tag later) * **Show tag:** * `$ git show` * Tagger info, date of tag, tag message * Commit info. * **Checkout tag:** * `$ git checkout v2.0.0` * No new commits (unreachable) * `-b version2 v2.0.0` : **new** branch '`version2`'

Question 37

How do you **_remove a file_** from a **_remote repo_**?

Answer 37

* `git rm` - Remove files. * `--cached`: **stage for removal**, not working directory * `-r `: recursive removal of **working directory** * To remove it from a **remote repo(Github)**: ` ` 1. `git rm --cached ` 2. `git add ` 3. `git commit -m ""` 4. `git push -u origin master / git push` ` `

Question 38

How do you **_remove a file_** from a **_local repo_**?

Answer 38

1. `git rm --cached ` 2. `git add ` 3. `git commit -m ""`

Question 39

What is **_merge_** used for?

Question 40

What is the difference between a **_generator_** and an **_iterator_**?

Answer 40

* A generator is a **_subclass of an iterator_** that has an easier syntax. Limited functionality, not so general as `collections.Iterator` * There are two types: * Yield statement. * List like generators.

Question 41

What is the **_iterator protocol_**?

Answer 41

An iterator class definition should have the following 3 methods to **comply with the protocol**: 1. `__iter__()`: * `return self` (the iterator) 2. `__next__()`: * What happens in the next iteration? 3. `raise StopIteration:` * When should the iterations stop? * Must be raised by `__next__` method.

Question 42

What are the **_4 pillars of OOP_**?

Answer 42

1. **Encapsulation:** * class: * variables * methods * information hiding: \_\_private, \_protected, public * **GET / SET** methods 2. **Abstraction**: * User interacts with **methods**, **not implementation** 3. **Polymorphism:** * Static Polymorphism: * same name, different behavior * type * number * order * DynamicPo 4. **Inheritance:** * whatever * whatever

Question 43

What do you use the `reduce()` function for?

Answer 43

* `functools.reduce(function (two args), iterable)` * Applies a function in a cumulative manner yielding one final value. * More Pythonic solutions: * `sum(), math.prod(), max(), min(), all(), any()`

Question 44

What do you use the `filter()` function for?

Answer 44

* `fil = filter(function, iterable)` * Returns a that can be converted to a list. * The filter object contains the items of the function returns `True`.

Question 45

How do you **_define a custom Exception_**?

Answer 45

# **_Define custom Exceptions:_** `class CustomException(Exception):` `def __init__ (self, msg):` `super().__init__(msg)` **_Raise custom Exceptions:_** `def checkforexceptions(whatever):` `if condition:` `raise Exception`

Question 46

How do you **_call a custom exception_**?

Answer 46

**_Raise custom Exceptions:_** `def checkforexceptions(whatever):` `if condition:` `raise Exception`

Question 47

What would you use **_for-else_** or **_while-else loops_** for?

Question 48

Can you pass **_arguments to an Exception_**?

Question 49

_**Classify the Exceptions**:_

Answer 49

`Base Exception (not meant to be directly inherited by user-defined classes)` `⇒ Exception (built-in, non-system-exiting exceptions)` `⇒ ArithmethicError ` `ZeroDivisionError, FloatingPointError` `⇒ AssertionError ` `⇒ StopIteration` `⇒ ValueError` `Right type but an inappropriate value.` `⇒ TypeError ` `Operation or function is applied to an object of inappropriate type. ` `Raised by user code to indicate that an attempted operation on an object is not supported.` `⇒ LookupError` `⇒ IndexError` `Sequence subscript is out of range.` `⇒ KeyError` `Dictionary key is not found.` `⇒ OSError` `⇒ FileExistsError` `errno EEXIST` `⇒FileNotFoundError` `errno ENOENT` `⇒ KeyboardInterrupt` `⇒ SystemExit`

Question 50

What is a **_shell_**?

Answer 50

* Computer program which **exposes an operating system's services** to a human user or other program. * For example: * Windows Shell (Windows' GUI). * **CLI shells (Command Line Interface):** Bash (Unix) or CMD prompt in Windows.

Question 51

What is **_bash_**?

Answer 51

* Unix **CLI shell**. * Default login shell for most Linux distributions since 1989. * Replaced Bourne Shell (**Bourne Again sh - bash** (sh: name of the language)

Question 52

What is **_syntactic sugar_**?

Answer 52

It makes the language **"sweeter"** for human use: things can be expressed **more clearly, more concisel**y, or in an alternative style that some may prefer.

Question 53

What are some useful **_examples of syntactic sugar_**?

Answer 53

``` `x = something if condition else otherthing` # python ternary ``` ``` `a += 1` # equivalent to a = a + 1 ``` ``` `1 < x < 10` # equivalent to 1 \< x and x \< 10 ``` ``` `[x for x in range(10)]` # List comprehension ```

Question 54

What is an **_OrderedDict_,** and what is the difference with a regular **_Dictionary_**?

Answer 54

* Create: * `from collections import OrderedDict` * `dic = OrderedDict()` * Methods: * `dic.popitem()` * `dic.move_to_end(key)` * Equality: * Checks for keys and values but also **order of insertion.** * New operators for dictionaries in Python 3.9: * `|` merge * `|=` update

Question 55

What are the uses of the `yield` statement?

Answer 55

* When resumed, the **function remember where it was** before the last `yield` run. * Similar to `return`: * Return sends a specified value back to its caller whereas `yield` can produce a sequence of values. * `yield` expression is used when defining a generator function and thus can **only be used inside def.** * `yield` expressions are allowed anywhere in a `try` construct.

Question 56

What is a `bytearray`? What do you use them for?

Answer 56

* Always **created by calling the constructor**: * `bytearray(), bytearray(10), bytearray(range(20)), bytearray(b'Hi!').` * Basic **building block of a binary file**: pictures, music, video, etc. * **_Methods_**: * `bytes.decode(encoding="utf-8", errors="str")` * `# Regular sequence methods:` * `bytearray.count(sub[, start[, end]])` * `bytes.replace(old, new[, count])` * `bytes.find(sub[, start[, end]])` * `bytes.index(sub[, start[, end]])` * `bytes.lstrip([chars])` * `bytes.rsplit(sep=None, maxsplit=-1)` * `bytes.isalpha()`

Question 57

What are the different **_file open modes_**?

Answer 57

* `with open("file.ext", "xt"/"rt") as file:` * XARW: * "x": create * "a": append * "r": read * "w": write * "t": Text Mode * "b": Binary Mode * "+": Open to update

Question 58

What are the most common **_HTTP response status codes​_**?

Answer 58

1. Informational responses (100–199) 2. Successful responses (200–299) * **_200 OK:_** * GET: The resource has been fetched and is transmitted in the message body. * HEAD: The entity headers are in the message body. * PUT or POST: The resource describing the result of the action is transmitted in the message body. * TRACE: The message body contains the request message as received by the server. * **_201 Created:_** Resource created. 3. Redirects (300–399) 4. Client errors (400–499): * **_400 Bad Request:_** client error (e.g., malformed request syntax, deceptive request routing). * **_401 Unauthorized:_** request has not been applied because it lacks valid authentication credentials for the target resource. * **_403 Forbidden:_** server understood the request but refuses to authorize it. * **_404 Not Found:_** server can't find the requested resource. Links that lead to a 404 page are often called _broken or dead links._ 5. Server errors (500–599) * **_500 Internal Server Error:_** Server encountered an unexpected condition that prevented it from fulfilling the request. _Generic "catch-all" response_. Usually, this indicates the server cannot find a better 5xx error code to response. * **_503 Service Unavailable:_** Server is not ready to handle the request. Common causes are a _server that is down for maintenance or that is overloaded._

Question 59

Useful methods in **_OS module_**?

Answer 59

* **os:** _Rats Stabbed Wieners._ * `os.rename("old_file_name", "new_file_name")` * `os.stat("file_ name"): ` * `st_size = # size in bytes.` * `st_mtime = # last modified (timestamp).` ` ` * `os.walk(top="path"): ` * `# returns a tuple with the tree structure for iteration.` ` ` * **os.path:** _Beasts Discussed Indecent Spielberg._ * `os.path.basename("path")` * `os.path.dirname("path")` * `os.path.isdir("path")` * `os.path.splittext("path"): ` * `# returns a list with the path and the file extension.`

Question 60

Where do you find the `Path` **class**?

Answer 60

`from pathlib import Path` * A subclass of PurePath * Correspondence to tools in the `os` module: * `Path.cwd()` * `Path.stat()` * `Path.exists()` * `Path.is_dir()` * `Path.mkdir()` * `Path.open()` * `Path.touch()` * `p = Path(direccion.name)` * `with open(p, "rt", encoding="utf-8") as file:`

Question 61

Useful methods in `CSV` module?

Answer 61

* `csv.reader(csvfile, dialect='', **fmtparams)` * Reader object which will iterate over lines. * `csvfile`: any object that supports the iterator protocol and returns a string. * Dialect : 'excel', excel-tab', 'unix' ('\n' as line terminator and quoting all fields) * `csvreader.__next__()` * `csv.writer(csvfile, dialect='', **fmtparams)` * csvwriter.writerow(row) `**fmtparams` = Dialects and Formatting Parameters

Question 62

What are the different characteristics of the **3 programming paradigms**?

Answer 62

* **_Procedural programming, structured programming_** – * Specifies the steps a program must take to reach a desired state. * Use of global variables. * **_Functional programming_** – * Treat programs as evaluating mathematical functions and avoids state and mutable data. * Functions pass values, less global variables. * **_Object-oriented programming (OOP)_** – * Organizes programs as objects: instances, data structures consisting of datafields and methods together with their interactions.

Question 63

What are **_dunder methods_**?

Answer 63

* Special, predefined methods. (double underscore: \_\_init\_\_ or \_\_str\_\_). * There are **hundreds** of Special methods available to implement in Python. * The special methods provide a **common API** that allows developers to create interactive classes. * Create classes with native data structures behavior. 1. **Object Initialization:** * `__init__` 2. **Object Representation:** * `__repr__`: The “official” string representation of an object. This is how you would make an object of the class. The goal of \_\_repr\_\_ is to be unambiguous. * `__str__`: The “informal” or nicely printable string representation of an object. This is for the enduser. 3. **Iteration**: * **Sequences**: * `__len__`: \>\>\> len(obj) * `__getitem__`: \>\>\> obj[1] * `__reversed__`: reversed(obj) 4. **Arithmetic Operators:** * `__add__`: \>\>\> 1 + 2, (also: -, \*, /, //) 5. **Callable:** * `__call__`: \>\>\> obj() 6. **Delete:** * `__del__`: \>\>\> del(obj)

Question 64

Useful `list` methods?

Answer 64

* **Sequences**: support the `__len__` and `__getitem__` methods. Lists, tuples, ranges, strings, bytes. * **Common** **Sequence** methods (lists, tuples, ranges, strings, bytes- b''-ASCII): * `in, +, *, s[i], len(), index(), count(), min(), max(), sort()` * **Mutable** **Sequence** methods (lists, bytearray): * Direct assignation: `s[i] = x` * `del(), clear(), copy()` * `append(), insert(i, x), pop([i]), remove(), reverse()` * ​​**List** supports both sets of instructions.

Question 65

How do you **_turn off the computer_** using command line?

Answer 65

`> shutdown /s /t `: xxx time in seconds `> shutdown /p`: Immediate shutdown `> shutdown /a`: Abort shutdown

Question 66

What do you use the `global` keyword for?

Question 67

What is the difference between **_parameters_** and **_arguments_**?

Question 68

What is **_argument tuple packing_**?

Question 69

What is **_argument tuple unpacking_**?

Question 70

What is _**name mangling**?_

Question 71

What is the **_precedence order_** for the 3 types of ways of passing arguments to a function or method?

Question 72

Create some **_list comprehension_** arrays: * 4 rows x 5 columns * 1 row x 7 columns * 3 rows x 10 columns

Question 73

What is a `__pycache__` file? What is the name format for it?

Question 74

What is the special variable `__name__` used for?

Question 75

How do you raise an **_assertion error_**?

Answer 75

* `assert expression1, expression2 OR "TEXT"` * Debugging assertions into a program. * `raise AssertionError("Hola amiguitos")` * `>> AssertionError: Hola amiguitos`

Question 76

What is the expected output of the following code snippet? `assert False`

Answer 76

`assert False` `>> AssertionError` `assert True` `>>`

Question 77

What is **_Unicode_**?

Answer 77

* Backward compatible with ASCII. ≈ **1 million Code points.** * Processing, storage and interchange of text data in **any language. U+20AC, U+0800** * **Unicode Transformation Formats (UTF)**: UTF-8, UTF-16, and UTF-32. * 95% of websites as of 2020. Unicode Consortium.

Question 78

What is **_UTF-8_**?

Answer 78

* **1,112,064** code points * Lower numerical values Code Points (frequently used) ⇒ **fewer bytes.** * World Wide Web Consortium recommends UTF-8 as the **default encoding in XML and HTML**

Question 79

What are the **_restricted keywords_** in Python?

Answer 79

* 35 keywords: * from, import, with, as * class, def, lambda, global, local * for, while, if, elif, else, try, except, assert, raise, finally, * pass, continue, break, return, yield * and, or, not, is, in, non, del, True, False, None * await, async

Question 80

Please enlist all the different **_list comprehension - like_** data structures.

Answer 80

* **Set comprehension** (no duplicates, no particular order): * `>>> quote = "life, uh, finds a way"` * `>>> unique_vowels = {i for i in quote if i in 'aeiou'}` * **Dictionary comprehensions**: * `>>> squares = {i: i * i for i in range(10)}`

Question 81

Types of `lambda` expressions:

Answer 81

* `lambda [parameter_list] : expression` * **Characteristics:** * **Anonymous** function * Syntactic **Sugar**. * Wherever a **function** object is allowed. * Functional **paradigm**. * `def (parameters):` * `return expression`

Question 82

Most useful options for `pip install`:

Answer 82

* `pip install x_package == version` * `-U, --upgrade`: upgrade to the newest version * `--force-reinstall`: reinstall all packages (even if up-to-date) * `-r, --requirement `

Question 83

What is the difference between `index()` and `find()` for a string?

Answer 83

* Both have an identical syntax: * `"string".index("substring", start(int), end(int))` * `"string".find("substring", start(int), end(int))` * If `"substring"` is not found: * `index` returns `ValueError` * `find` returns `-1`

Question 84

What does `isinstance()` do?

Answer 84

* `isinstance(object, classinfo)` * `True`: if `object` is instance or subclass of `classinfo`

Question 85

What is a **_closure_**? Why would I want to use them?

Question 86

Most frequent **_Linux errors_**:

Answer 86

* **2 -** E**NOENT:** No such file or directory * **9-** E**BADF:** Bad file number (unopened stream) * **13** - E**ACCES**: Permission denied (read only) * **17** - E**EXIST**: File exists * **21** - E**ISDIR**: Is a directory * **24** - E**MFILE**: Too many open files * **27** - E**FBIG**: File too large * **28** - E**NOSPC**: No space left on device

Question 87

What is `errno`?

Answer 87

* Module standard **errno system symbols** (`linux/include/errno.h`) * **errno.errorcode:** * `errno.errorcode[errno.EPERM] ` * `>> 'EPERM'`

Question 88

What is `sterror`?

Answer 88

* `os.strerror(errno.ENOSPC)` * Return the error message corresponding to the error code in code. * On platforms where `strerror()` returns `NULL` when given an unknown error number, `ValueError` is raised.

Question 89

What is **_encapsulation_**?

Answer 89

* **class**: * variables * methods * Information hiding: `__private, _protected, public` * **GET / SET** methods

Question 90

Useful **_classes - methods_** of `shelve` module:

Question 91

What are the **OAuth 2.0 roles**?

Answer 91

1. Resource owner: End user ⇒ Credentials ⇒ Limited scope 2. Client: App. 3. API's Resource Server: Hosts user's information. 4. API's Auth Server: Access tokens.

Question 92

Explain the **OAuth2.0 endpoints**:

Answer 92

1. **Authorization Endpoint:** * Used by Auth code (returns code) and Implicit (returns token) grants. 2. **Token Endpoint:** 1. Client presents **_Auth code or Refresh Token_**, Auth server grants access. 2. Used by Auth code, resource owner, client credentials. 3. **Redirection Endpoint:** * OAuth redirects to a URI.

Question 93

Describe the **Auth Code grant**:

Answer 93

1. **Auth request:** * Client sends: * Client ID. * Scope. * State. * Redirection URI. 2. **Auth grant:** * Auth code is sent to **_Auth server_**. An access/refresh token will be issued. 3. **Access Token:** * The client sends the access token to the **_Resource server_** to have access to resources.

Question 94

Explain the basic process to configure **OAuth2.0 with a Google Cloud API**:

Answer 94

1. Create an **_OAuth2.0 client_**: * Client ID & secret. 2. Configure **_consent screen_**: * App name. * Developer email. * Scopes. 3. **_App type:_** * Local web server. 4. **_Add redirect URI_**. * http://localhost.8080/ (same port as in run local server). 5. **_Get client ID & secrets_** * JSON.

Question 95

How do you use a **Google API using OAuth2.0**?

Answer 95

1. **Install:** * `pip install google-auth-oauthlib` * `pip install google-api-python-client.` 2. **Import:** * `from google_auth_oauthlib.flow import InstalledAppFlow` * `from googleapiclient.discovery import build` 3. **Instance the Auth Flow:** 1. `self.flow = InstalledAppFlow.from_client_secrets_file( "creds_00.json", scopes=[] )` 4. **OAuth2.0:** 1. Ask user auth. * `self.flow.run_local_server( port=8080, prompt="consent", authorization_prompt_message="" )` 2. Get credentials , access-refresh token: * `self.flow.credentials` 5. **​​Service:** * `self.service = build("classroom", "v1", credentials=creds)` * `request = self.service.courses().list(courseStates="ACTIVE", teacherId="me")` * `response = request.execute()`