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Python Basics

Room information

Type: Walkthrough
Difficulty: Easy
Tags: -
Meta Tags: Walkthrough, Walk-through, Write-up, Writeup
Subscription type: Free
Description:
Using a web-based code editor, learn the basics of Python and put your knowledge 
into practice by eventually coding a short Bitcoin investment project.

Room link: https://tryhackme.com/room/pythonbasics

Solution

Task 2 - Hello World

Output to the screen (stdout) is done in Python with the print statement

print("Hello World")

Task 3 - Mathematical Operators

Most operators are as expacted in Python

Operator Syntax Example
Addition + 1 + 1 = 2
Subtraction - 5 - 1 = 4
Multiplication * 10 * 10 = 100
Division / 10 / 2 = 5
Modulus % 10 % 2 = 0
Exponent ** 5**2 = 25

Addition

print(21 + 43)

Subtraction

print(142 - 52)

Multiplication

print(10 * 342)

Squared/Exponent

print(5 ** 2)

Task 4 - Variables and Data Types

Now we introduce variables. There is no special syntax or prefix for variables.

height = 200
height += 50
print(height)

Task 5 - Logical and Boolean Operators

Logical operators allow assignment and comparisons to be made and are used in conditional testing (such as if statements).

Logical Operation Operator Example
Equivalence == if x == 5
Less than < if x < 5
Less than or equal to <= if x <= 5
Greater than > if x > 5
Greater than or equal to >= if x >= 5

Boolean operators are used to connect and compare relationships between statements.
Like an if statement, conditions can be true or false.

Boolean Operation Operator Example
Both conditions must be true for the statement to be true AND if x >= 5 AND x <= 100Returns TRUE if x isa number between 5 and 100
Only one condition of the statement needs to be true OR if x == 1 OR x == 10Returns TRUE if X is 1 or 10
If a condition is the opposite of an argument NOT if NOT yReturns TRUE if the y value is False

Task 6 - Introduction to If Statements

Project description

    In this project, you'll create a program that calculates the total
    cost of a customers shopping basket, including shipping.

    - If a customer spends over $100, they get free shipping
    - If a customer spends < $100, the shipping cost is $1.20 per kg of the baskets weight

    Print the customers total basket cost (including shipping) to complete this exercise.

Python code

customer_basket_cost = 34
customer_basket_weight = 44

# Write if statement here to calculate the total cost
if customer_basket_cost <= 100:
  shipping = customer_basket_weight * 1.2
  total_cost = customer_basket_cost + shipping
else:
  total_cost = customer_basket_cost

print(total_cost)

Task 7 - Loops

While Loops

While loop example

i = 1
while i <= 10:
     print(i)
     i = i + 1

For Loops

For loop example

websites = ["facebook.com", "google.com", "amazon.com"]
for site in websites:
     print(site)

Code

for i in range(51):
     print(i)

Task 8 - Introduction to Functions

Function examples

def sayHello(name):
     print("Hello " + name + "! Nice to meet you.")

sayHello("ben") # Output is: Hello Ben! Nice to meet you

and

def calcCost(item):
     if(item == "sweets"):
          return 3.99
     elif (item == "oranges"):
          return 1.99
     else:
          return 0.99

spent = 10
spent = spent + calcCost("sweets")
print("You have spent:" + str(spent))

Project description

    In this project, you'll create a program that that tells
    you when the value of your Bitcoin falls below $30,000.

    You will need to:
    - Create a function to convert Bitcoin to USD
    - If your Bitcoin falls below $30,000, print a message.

    You can assume that 1 Bitcoin is worth $40,000

Python code

investment_in_bitcoin = 1.2
bitcoin_to_usd = 40000

# 1) write a function to calculate bitcoin to usd
def bitcoinToUSD(bitcoin_amount, bitcoin_value_usd):
  usd_value = bitcoin_amount * bitcoin_value_usd
  return usd_value

investment_in_usd = bitcoinToUSD(investment_in_bitcoin, bitcoin_to_usd)
if investment_in_usd <= 30000:
  print("Investment below $30,000! SELL!")
else:
  print("Investment above $30,000")

Note that you must use their template litterly. You cannot change the variable or function names to something different!

Task 9 - Files

To read the entire contents of a file (all at once)

f = open("file_name", "r")
print(f.read())

To append to an existing file

f = open("demofile1.txt", "a") # Append to an existing file
f.write("The file will include more text..")
f.close()

To create and write to a new file

f = open("demofile2.txt", "w") # Creating and writing to a new file
f.write("demofile2 file created, with this content in!")
f.close()

Code

f = open("flag.txt", "r")
print(f.read())

Task 10 - Imports

To import and use libraries

import datetime
current_time = datetime.datetime.now()
print(current_time)

For additional information, please see the references below.

References