Understanding Python Function Arguments and Exploring List Methods: A Beginner's Guide

Function Arguments:

Functions in Python accept arguments to work with. There are four main types:

1. Default Arguments:

   • You can set a default value for arguments.

   • If you don't provide a value during the function call, the default is used.

    def greet(name, role="student"):
        print(f"Hello {name}, you are a {role}")
    greet("Safia")  # Output: Hello Safia, you are a student
    greet("Aman", "teacher")  # Output: Hello Aman, you are a teacher

2. Keyword Arguments:

   • Use key=value to assign arguments directly by their name.

   • The order doesn’t matter.

    def introduce(name, age, city):
        print(f"{name} is {age} years old from {city}.")
    introduce(age=24, city="Hyderabad", name="Safia")  
    # Output: Safia is 24 years old from Hyderabad.

3. Required Arguments:

   • Arguments must be passed in the correct order and quantity.

    def calculate_sum(a, b, c):
        print(a + b + c)
    calculate_sum(10, 20, 30)  # Output: 60  
    # calculate_sum(10, 20)  # Error: Missing 1 required argument.

4. Variable-Length Arguments:

   • For passing any number of arguments, use * or **.

     • * for tuple-based arguments:

         def add_numbers(*nums):
             print(sum(nums))
         add_numbers(10, 20, 30, 40)  # Output: 100
       

     • ** for dictionary-based arguments:

         def show_details(**info):
             print(info)
         show_details(name="Safia", age=24, city="Hyderabad")  
         # Output: {'name': 'Safia', 'age': 24, 'city': 'Hyderabad'}
       

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return Statement:

The return statement sends back a result from the function.

• Without return, functions only perform tasks; with return, they give a value back.

    def add(a, b):
        return a + b
    result = add(10, 20)  
    print(result)  # Output: 30
  

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Summary:

• Default Arguments: Use default values if no value is provided.

• Keyword Arguments: Pass arguments in any order using key=value.

• Required Arguments: Pass all arguments in the correct order and number.

• Variable-Length Arguments: Use * for tuples, ** for dictionaries to handle extra arguments.

• return Statement: Sends a result back to the calling code.

Practice:

def greet (name, role):
    print(f"Hello {name}, You are a {role}")
greet("safia","teacher")

def introduce (name,age,city):
    print(f"{name} is {age} years old and from {city}.")
introduce(age=24, name="safia", city="Hyderabad")


def calculate_sum(a, b, c):
    print(a + b + c)
calculate_sum(12,15,10)

def add_numbers (*nums):
    print(sum(nums))
add_numbers(10,20,30,40,50)

def show_detail(**info):
    print(info)
show_detail(name = "safia", age = 24, city = "Hyderabad")

def add(a, b):
    return a + b
result = add(60,10)
print(result)

Introduction to Lists in Python :

Python Lists: Simplified Explanation and Examples

Definition:

• A list is an ordered collection of items.

• You can store multiple items in a single variable.

• Lists are written in square brackets [] and items are separated by commas.

• Lists are mutable, meaning their content can be changed.

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Key Concepts

1. Creating a List
   Example:

    numbers = [1, 2, 3, 4]
    colors = ["Red", "Green", "Blue"]
    print(numbers)
    print(colors)
   

   Output:

    [1, 2, 3, 4]  
    ['Red', 'Green', 'Blue']
   

2. List Indexing

   • Each item in a list has an index.

   • Positive indexing starts from 0.

   • Negative indexing starts from -1 (from the end).
     Example:

    colors = ["Red", "Green", "Blue"]
    print(colors[0])  # Positive Index
    print(colors[-1]) # Negative Index

Output:

    Red  
    Blue

3. Check if Item Exists
   Use in keyword to check for an item.
   Example:

    colors = ["Red", "Green", "Blue"]
    if "Red" in colors:
        print("Red is present.")
   

   Output:

    Red is present.
   

4. Slicing a List

   • Use [start:end:step] to access a portion of the list.

   • Start: Index to begin.

   • End: Index to stop (not included).

   • Step: Jump index (default is 1).

Example:

    animals = ["cat", "dog", "bat", "mouse", "pig"]
    print(animals[1:4])  # From index 1 to 3
    print(animals[::2])  # Every 2nd item

Output:

    ['dog', 'bat', 'mouse']  
    ['cat', 'bat', 'pig']

5. List Comprehension

   • Short way to create a new list from an existing one.
     Syntax:

    new_list = [expression for item in iterable if condition]

Example:

    names = ["Milo", "Sarah", "Bruno"]
    names_with_o = [name for name in names if "o" in name]
    print(names_with_o)

Output:

    ['Milo', 'Bruno']

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Summary

• Lists store multiple items and are changeable.

• Indexing helps access items: Positive [0, 1, 2...], Negative [-1, -2, -3...].

• Use in to check if an item exists.

• Slicing allows accessing parts of the list using [start:end:step].

• List Comprehension makes creating filtered lists easy and efficient.

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Easiest Example

fruits = ["apple", "banana", "cherry", "date"]
print(fruits[1])         # Accessing with index
print(fruits[-1])        # Accessing last item
print(fruits[1:3])       # Slicing (index 1 to 2)
print([f for f in fruits if "a" in f])  # List comprehension

Output:

banana  
date  
['banana', 'cherry']  
['apple', 'banana', 'date']

Practice:

numbers = [1,2,3,5,8,0] #list
fruits = ["apple","banana","cherry","coconut","grapes"] #list
print(numbers,fruits)

print(numbers[3:5]) #indexing
print(numbers[4:-1]) #negative indexing
print(numbers[-4]) #negative indexing

if "black" in fruits:
    print("yes bhai")  # check if item existD
else:
    print("nahi hai bhai")

print(fruits[1:4])  #start to end
print(fruits[::2]) #step

names = ["safia","sadaf","puja","najiya","amir","dev"] # list comprehension
names_with_e = [n for n in names if "e" in n]
print(names_with_e)

Python List Methods

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1. list.sort()

• What it does: Sorts the list in ascending order.

• Default: Ascending, but can sort in descending with reverse=True.

Example 1 (Ascending):

numbers = [5, 3, 8, 1]
numbers.sort()
print(numbers)  # Output: [1, 3, 5, 8]

Example 2 (Descending):

numbers = [5, 3, 8, 1]
numbers.sort(reverse=True)
print(numbers)  # Output: [8, 5, 3, 1]

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2. list.reverse()

• What it does: Reverses the list (not sorting).

Example:

numbers = [5, 3, 8, 1]
numbers.reverse()
print(numbers)  # Output: [1, 8, 3, 5]

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3. list.index(item)

• What it does: Returns the index of the first occurrence of an item in the list.

Example:

colors = ["red", "green", "blue", "green"]
print(colors.index("green"))  # Output: 1

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4. list.count(item)

• What it does: Counts how many times an item appears in the list.

Example:

colors = ["red", "green", "blue", "green"]
print(colors.count("green"))  # Output: 2

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5. list.copy()

• What it does: Creates a copy of the list.

Example:

colors = ["red", "green", "blue"]
new_colors = colors.copy()
print(new_colors)  # Output: ['red', 'green', 'blue']

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6. list.append(item)

• What it does: Adds an item at the end of the list.

Example:

colors = ["red", "green"]
colors.append("blue")
print(colors)  # Output: ['red', 'green', 'blue']

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7. list.insert(index, item)

• What it does: Adds an item at a specific position.

Example:

colors = ["red", "blue"]
colors.insert(1, "green")  # Insert at index 1
print(colors)  # Output: ['red', 'green', 'blue']

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8. list.extend(other_list)

• What it does: Adds all items of another list to the current list.

Example:

colors = ["red", "green"]
rainbow = ["blue", "yellow"]
colors.extend(rainbow)
print(colors)  # Output: ['red', 'green', 'blue', 'yellow']

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9. Concatenating Two Lists

• What it does: Joins two lists with the + operator.

Example:

colors1 = ["red", "green"]
colors2 = ["blue", "yellow"]
print(colors1 + colors2)  # Output: ['red', 'green', 'blue', 'yellow']

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Summary of Methods:

Practice:

numbers = [45,56,78,90,356,70,13,3648]
print(numbers)
numbers.sort()
print(numbers) #asscending_order

numbers.sort(reverse=True) #desending_order
print(numbers)

numbers.reverse() #not shorting only reverse
print(numbers)

fruits = ["apple","banana","grapes","guava"] #return the index of the first occurance of an item in the list
print(fruits.index("guava"))

print(fruits.count("banana")) #count the banana how many times it written

new_fruits = fruits.copy()  #create a copy of the list
print(new_fruits)

num = [1,2,3,4,5] #append the number
num.append(6)
print(num)

colours = ["red","blue"] #add and item in a list
colours.insert(1,"orange")
print(colours)

colours = ["red","blue"]
rainbow = ["yellow","brown"]
colours.extend(rainbow)  #add the list

name = ["safia","sadaf"]
name1 = ["Amir","ali"]
print(name + name1)