Day - 5 Python Loops

Using the for loop with Python Lists

Using a for loop with Python lists allows you to iterate through

each element in the list, one at a time.

This is a fundamental way to work with lists in Python,

making it easier to process or manipulate the elements.

---

1. Iterating Over List Items

You can use a for loop to access and perform operations on each item in the list.

Example:

fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

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2. Using the range() Function

Sometimes, you want to iterate using the index of the items. You can use the range() function along with the len() function to achieve this.

Example:

fruits = ['apple', 'banana', 'cherry']
for i in range(len(fruits)):
    print(f"Index {i}: {fruits[i]}")

Output:

Index 0: apple
Index 1: banana
Index 2: cherry

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3. Performing Operations on List Items

We can perform calculations, modifications, or any other operations on the elements.

Example:

numbers = [1, 2, 3, 4, 5]
squared_numbers = []
for num in numbers:
    squared_numbers.append(num ** 2)
print(squared_numbers)

Output:

[1, 4, 9, 16, 25]

4. Nested for Loops with Lists

When working with nested lists (lists within lists), use nested for loops.

Example:

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]
for row in matrix:
    for item in row:
        print(item, end=' ')

Output:

1 2 3 4 5 6 7 8 9

---

Overview

Use a for loop to iterate over each element in a list.

Access elements by index using range() .

max() Function in Python

The max() function in Python is used to find the maximum value in a sequence or among multiple values. It works with various data types, including numbers, strings, and more.

Return Value

The function returns:

• The largest item in the iterable.

• The largest of the provided arguments.

Examples

1. Maximum in a List

numbers = [10, 20, 30, 40, 50]
print(max(numbers))

Output

50

2. Maximum Among Multiple Values

print(max(3, 7, 2, 9))

Output

9

for loops and the range ( ) function in Python

For Loops in Python

A for loop in Python is used to iterate over a sequence

(like a list, tuple, string, or range) and execute a block of code

for each item in the sequence.

• variable: Takes the value of each item in the sequence, one by one.

• sequence: The data structure or iterable you want to loop over.

Example:

Looping Through a List

fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
    print(fruit)

Output:

apple
banana
cherry

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The range() Function

The range() function generates a sequence of numbers, commonly used with for loops. It doesn't create a list but provides a range object that is iterable.

• start: The starting number (inclusive). The default is 0.

• stop: The ending number (exclusive). This is required.

• step: The increment (default is 1).

Examples of range()

1. Simple Range

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

   Output:

    0
    1
    2
    3
    4
   

2. Range with Start and Stop

    for i in range(2, 6):
        print(i)
   

   Output:

    2
    3
    4
    5
   

3. Range with Step

    for i in range(0, 10, 2): 
        print(i)
   

   Output:

    0
    2
    4
    6
    8
   

4. Range in Reverse

    for i in range(10, 0, -2):  
        print(i)
   

   Output:

    10
    8
    6
    4
    2
   

Key Points

1. For Loop: Iterates through each item in a sequence.

2. Range Function: Generates a sequence of numbers, which can be

   customized using start, stop, and step values.

3. Combination: Use range() with for loops for precise control over iteration.

   What’s the next milestone?

   On Day 6 of the 100 Days of Python, I will learn about Python functions and Karel.