Python

1. Input and Output

Python Function	Description
input()	Takes input from the user as a string.
print()	Displays output on the screen.

Example:

name = input("Enter your name: ")
print("Hello,", name)

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2. Variables and Data Types**

Data Type	Description	Example
int	Integer numbers	x = 10
float	Floating-point numbers	pi = 3.14
complex	Complex numbers	z = 2 + 3j
str	String (text)	name = "Alice"
str	String (text)	name = "Bob"
str	String (text)	name = 'Bob'
str	String & Multiline string (text)	name = """Bob"""
str	String & Multiline string(text)	name = '''Bob'''
bool	Boolean value: True or False	is_valid = True
list	Ordered, mutable sequence	fruits = ["apple", "banana"]
tuple	Ordered, immutable sequence	coordinates = (10, 20)
range	Sequence of numbers	r = range(5)
dict	Key-value pairs	person = {"name": "Alice", "age": 25}
set	Unordered collection of unique items	colors = {"red", "green"}
frozenset	Immutable version of set	frozen = frozenset([1, 2, 3])
bytes	Immutable sequence of bytes	b = b"hello"
bytearray	Mutable sequence of bytes	ba = bytearray(5)
memoryview	View over binary data	mv = memoryview(bytes(5))
NoneType	Represents the absence of a value	value = None

Python manages memory automatically (no malloc/free like C). Garbage collection is built-in.

2.1. Main cast functions

x = str(1) # Convert to string
x = int("1") # Convert to int
x = float("1.1") # Convert to float

# String to bytes (encoding)
text = "Hello World"
encoded = text.encode('utf-8')  # or 'ascii', 'utf-16', etc.
print(encoded)  # Output: b'Hello World'

# Bytes to string (decoding)
decoded = encoded.decode('utf-8')
print(decoded)  # Output: Hello World

3. Control Structures

num = 7
if num > 0:
    print("Positive")
elif num == 0:
    print("Zero")
else:
    print("Negative")

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4. Loops

for i in range(1, 6):
    print(i)

while True:
    print("ciao")

5. Functions

def add(a, b):
    return a + b

def print_something(a, b):
    print(a+b)

def nothing(a, b):
    pass

print(add(3, 4))

5.1. Type hints:

def add(a : int, b : int) -> str:
    return str(a + b)

6. File Handling

Function	Description
open()	Opens a file. Modes: "r", "w", "a", etc.
.read(), .readlines(), .write()	Reads from/writes to file.
.close()	Closes the file. (Not needed if using with statement).

with open("data.txt", "w") as f:
    f.write("Hello, File!")

When the program exits from the with block, the f.close() is automatically called saving also the file content.

7. Object-Oriented Programming

Example:

class Person:
    def __init__(self, name, age):
        # Constructor
        self.name = name # Object attribute
        self.age = age # Object attribute

    def method_name(self, years_gap):
        self.age += years_gap

p = Person("Alice", 25) # Instatiation of an object
print(p.name, p.age) # Access object attributes
p.method_name(10) # Method call

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10. Main Function (Optional in Python)

Feature	Description
if __name__ == "__main__":	Python runs code here only if script is executed directly (not imported).

If you run the file with this instruction, the interpreter will execute the code inside the code block:

python3 file.py

If you import the file in another python script, the "if" code block will not be executed.

Example:

def greet():
    print("Hello!")

if __name__ == "__main__":
    greet()