Python Notes

What is a virtual environment?

It represents an isolated environment to manage dependencies without them conflicting with other projects.

How to create a venv?

In the root of your new project, run the following command in your terminal: python -m venv .venv

How to use venv?

After entering venv, install the project dependencies (modules, libs in general)

How to exit/deactivate venv?

To exit venv, simply execute the following command, or close the terminal.

deactivate

List dependencies with requirements.txt

To install the requests module, run:

pip install requests

Listing installed dependencies:

To view the dependencies and their installed versions:

pip freeze

Saving dependencies in requirements.txt

Store all installed dependencies:

pip freeze > requirements.txt

What are dictionaries in python?

Dictionaries in python is a type of structure that stores information in key and value pairs. Each key is unique for accessing and selecting the corresponding value.

person = {
       "name": "Mattheus",
       "age": 21,
       "contact": "https://www.linkedin.com/in/mattheuspereira/"
}

Information grouping

Dictionaries are useful for organizing and retrieving data efficiently.

print(f"Name: { person['name'] }")
print(f"Age: { person['age'] }")
print(f"Contact: { person['contact'] }")

Note that with a single person variable, we can store different types of information, such as name, age and contact.

List of dictionaries

We can also build dictionary lists and display the information through loops:

creating a list of dictionaries

people = [
       { "name": "Mattheus", "age": 27 },
       { "name": "Jessica", "age": 32 },
       { "name": "Lucas", "age": 18 },
]

displaying users in a loop in the list

for p in people:
       print(f"Name: { p['name'] }, Age: { p['age'] }")


Name: Matheus, Age: 21
Name: Jessica, Age: 28
Name: Lucas, Age: 30

Adding new information to the dictionary

We can add new information to the dictionary as follows:

creating a dictionary with initial information

player = {
       "name": "Mattheus",
       "level 1
}

adding new keys and values to the dictionary

player['life'] = 100
player['damage'] = 25.2
player['clan'] = "Pythonists"
player['leader_clan'] = True

displaying the dictionary with the added information

print(player)

###Exit

{
       'name': 'Mattheus',
       'level 1,
       'life': 100,
       'damage': 25.2,
       'clan': 'Pythonists',
       'leader_clan': True
}

##Conditionals

Changes the execution flow of our programs

Structure of a conditional

if (condition) // do something

or else (other condition) // do something

otherwise // do something

The condition must be true for the instruction block to be executed.
We can use operators, variables, and even call functions with returns to validate a conditional.

Examples using python

age = 18

if age >= 18
       print("adult")

elif age >=16:
       print("teen")

elif age >=13:
       print ("pre teenager")

else:
       print("child")

In the example above, I created a variable called age, which takes the value of 18.

Then I created some conditions to display a message

If the age is greater than or equal to 18: adult
Or, if the age is greater than or equal to 16: teenager
Or, if the age is greater than or equal to 13: pre-adolescent
Otherwise: child

Lists

These are ordered collections of items in Python
The indices in a list can be of different types and can be accessed through indexes.

Example using Python

´´´ fruits = ['apple', 'banana', 'orange'] print (fruits[0]) ´´´

Repetitions (loops)

'for' and 'while' are control structures used to execute a block of code multiple times.
'for' is generally used when the number of iterations is known in advance.
'while is when the stopping condition is not known in advance.

Example of 'for' in Python

for number in range (5): print(number)

'while' example in python

counter = 0 while counter <5: print (counter) counter +=1

Dictionaries

Dictionaries are data structures that store key-value pairs
Each value is associated with a unique key, allowing quick access to data.

Example used python

´´´student={'name': 'João', 'age':20, 'course': 'Engineering'} print(student['age'])

Functions and parameters

Functions are blocks of code that perform a specific task and can be reused in different parts of the program.
Parameters are values that can be passed to a function to customize its behavior.

Python example

´´´ def greeting(name): print(f''Hello, {name}'')

greeting('Maria') ´´´

mattheusp/Python-Notes