Python Basics: Variables, Operators & Conditionals

Variables and Data Types

• To correctly declare a variable, assign the value "João" directly to the variable name: nome = "João".
• The int data type stores integer numbers
• Given the code x = 5.0, the type of the variable x is float.
• The expression type("42") results in str, indicating the data type is string
• To transform the integer 10 into a decimal (float), use float(10).

Operators and Expressions

• The result of the expression 10 % 3 is 1 because it calculates the remainder of the division.
• The % operator calculates the remainder of a division.
• The ** operator calculates the power of a number.
• The expression 2 + 3 * 4 results in 14 because multiplication is performed before addition.
• The result of "Python" + " " + "é legal" is "Python é legal".

Conditional Structures

• The keyword if defines a condition in Python.
• The symbol == represents equality.
• The correct structure for a conditional block is if condition: commands.
• The correct way to write an if-else block is if condition: commands else: commands.
• A logical operator combines boolean conditions.

Repetition Structures

• The for structure repeats a code a specific number of times.
• A loop that goes through the numbers 1 to 10 uses for i in range(1, 11):.
• The command break immediately ends a loop.
• for is used to traverse sequences, while while executes as long as a condition is true; this is the primary difference between them
• The command continue jumps to the next iteration in a loop.

Lists and Collections

• An empty list can be created using list() or [].
• To access the third element of a list called frutas, use frutas[2].
• The append() method adds an element to the end of a list.
• The length of a list called alunos is obtained using len(alunos).
• The result of [1, 2, 3] + [4, 5] is [1, 2, 3, 4, 5].

Functions

• A function is defined in Python using def minhaFuncao():.
• A function parameter is a value sent to a function when it is called.
• To call a function named calcular that takes two arguments, use calcular(arg1, arg2).
• The keyword return returns a value from a function.
• If a function doesn't have a return instruction, it returns None.

Strings

• The first character of a string called texto is accessed using texto[0].
• To convert a string to uppercase, use the upper() method.
• The split() method divides a string into a list of substrings.
• To verify if a string contains a substring, use "string" in "substring".
• An f-string is a string that allows including Python expressions inside curly braces {}.

Input and Output

• The input() function obtains user input.
• To display a message on the screen, use print("Mensagem").
• The correct way to format the output to display the value of the variable idade is print(f"Idade: {idade}").
• To read an integer number from user input, use int(input()).
• If you use input() without converting the result, the program returns a string.

Dictionaries

• An empty dictionary is created using dict() or {}.
• To access the value associated with the key "nome" in a dictionary called pessoa, use pessoa["nome"] or pessoa.get("nome").
• A new key-value pair is added to a dictionary using dicionario[chave] = valor.
• To check if a key exists in a dictionary called config, use "chave" in config.
• If you try to access a non-existent key in a dictionary, a KeyError is raised.

Errors and Exceptions

• Exceptions in Python are handled using try: ... except: ....
• A ValueError occurs when a function receives an argument with the correct type but an inappropriate value.
• The finally clause in a try-except block always executes, regardless of whether an exception occurs or not.

Modules and Libraries

• To import a module called math, use import math.
• The random module generates random numbers.