Python language learning

1. Python Data Structure
Lists
Creating a List
my_list = [1, 2, 3, 'a', 'b', 'c']


Accessing Elements
print(my_list[0]) # Output: 1
print(my_list[-1]) # Output: 'c' (last element)




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Slicing
print(my_list[1:3]) # Output: [2, 3]
print(my_list[:2]) # Output: [1, 2] (first two elements)

Modifying Elements
my_list[0] = 10

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Adding Elements
my_list.append(5)
my_list.insert(1, 'x')
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# Add to the end
# Insert 'x' at index 1




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Removing Elements
my_list.remove(3) # Remove element with value 3
element = my_list.pop(2) # Remove and return element at index 2
my_list.clear() # Remove all elements

Other List Methods
my_list.sort() # Sort list in ascending order
my_list.reverse() # Reverse the list
my_list.count('a') # Count occurrences of 'a'
len(my_list) # Get the number of elements



2. Tuples
Creating a Tuple
my_tuple = (1, 2, 3, 'a', 'b')

Accessing Elements
print(my_tuple[1]) # Output: 2

,Slicing
print(my_tuple[1:3]) # Output: (2, 3)

Tuple Unpacking
a, b, c = (1, 2, 3) # Assign 1 to a, 2 to b, 3 to c

Tuple Methods
my_tuple.count(1) # Count occurrences of 1
my_tuple.index('a') # Find the index of 'a'

Note: Tuples are immutable, meaning elements cannot be modified after creation.




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3. Sets
Creating a Set

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my_set = {1, 2, 3, 'a'}

Adding/Removing Elements
my_set.add(4) # Add an element
my_set.remove(2) # Remove an element (raises error if not found)




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my_set.discard(5) # Remove element if present (no error if not
found)

Set Operations
set1 = {1, 2, 3}
set2 = {3, 4, 5}

union = set1 | set2 # Union: {1, 2, 3, 4, 5}
intersection = set1 & set2 # Intersection: {3}
difference = set1 - set2 # Difference: {1, 2}

Other Set Methods
set1.isdisjoint(set2) # Check if sets have no elements in common
set1.issubset(set2) # Check if set1 is a subset of set2
len(my_set) # Get the number of elements



4. Dictionaries
Creating a Dictionary
my_dict = {"name": "John", "age": 25, "city": "New York"}

, Accessing Elements
print(my_dict["name"]) # Output: John
print(my_dict.get("age")) # Output: 25


Adding/Modifying Elements
my_dict["email"] = "" # Add new key-value pair
my_dict["age"] = 26 # Modify existing value

Removing Elements
del my_dict["city"] # Delete the key-value pair 'city'
my_dict.pop("email") # Remove and return value of 'email'




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my_dict.clear() # Remove all elements

Iterating Over a Dictionary




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for key, value in my_dict.items():
print(key, value)

Dictionary Methods




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my_dict.keys() # Get all keys
my_dict.values() # Get all values
my_dict.items() # Get all key-value pairs



2. OBJECT ORIENTED PROGRAMMING
1. Creating a Class
class MyClass:
def __init__(self, name):
self.name = name

def greet(self):
# Constructor
# Instance attribute

# Instance method
print(f"Hello, {self.name}!")
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# Creating an object (instance of MyClass)
obj = MyClass("Alice")
obj.greet() # Output: Hello, Alice!

__init__ Method (Constructor)

 Used to initialize objects.

class Person:
def __init__(self, name, age):
self.name = name
self.age = age



2. Class Attributes vs Instance Attributes