enumerate() in python

"""The `enumerate()` function in Python is a built-in utility that allows you to loop through an iterable 
(like a list, tuple, or string) and get both the index and the corresponding value in each iteration.
This is particularly useful when you need both the position and the element during a loop.
---
#Syntax:-"""
enumerate(iterable, start=0)

"""
- iterable: The object you want to iterate over (e.g., list, tuple, string, etc.).
- start: The starting index (default is `0`).
---
How It Works:-
enumerate() returns an enumerate object, which is an iterator yielding pairs of an index and the corresponding value from the iterable.
"""


#Basic Example:-

fruits = ['apple', 'banana', 'cherry']
for index, value in enumerate(fruits):
    print(f"Index {index}: {value}")
    
"""Output:

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


- Using the start Parameter
You can specify a custom starting index using the start argument.
"""

fruits = ['apple', 'banana', 'cherry']
for index, value in enumerate(fruits, start=1):
    print(f"Position {index}: {value}")

"""
Output:-

Position 1: apple
Position 2: banana
Position 3: cherry
---



*Practical Use Cases:-

1. Processing Lists with Indices
Instead of manually tracking the index with a counter, you can use enumerate():
"""

names = ['Alice', 'Bob', 'Charlie']
for i, name in enumerate(names):
    print(f"Processing {name} at index {i}")
---



"""
2. **Modifying Elements by Index**
If you need to update elements at specific indices:
"""

numbers = [10, 20, 30]
for i, value in enumerate(numbers):
    numbers[i] = value * 2
print(numbers)

"""
Output:-
[20, 40, 60]
---



3. **Combining Enumerate with Other Iterables**
When iterating over multiple iterables:
"""

questions = ['What is your name?', 'How old are you?', 'Where do you live?']
answers = ['Alice', '25', 'Paris']
for i, (question, answer) in enumerate(zip(questions, answers), start=1):
    print(f"Q{i}: {question}")
    print(f"A{i}: {answer}\n")

"""
Output:-
Q1: What is your name?
A1: Alice

Q2: How old are you?
A2: 25

Q3: Where do you live?
A3: Paris
---

4. **Working with Strings**
You can iterate over characters in a string with their positions:
"""
message = "hello"
for i, char in enumerate(message):
    print(f"Character at index {i}: {char}")

"""
Output:-
Character at index 0: h
Character at index 1: e
Character at index 2: l
Character at index 3: l
Character at index 4: o
---

5. **Filtering with Indices**
Use `enumerate()` to process specific items based on their indices:
"""

numbers = [10, 20, 30, 40, 50]
for i, num in enumerate(numbers):
    if i % 2 == 0:
        print(f"Index {i} has value {num}")

"""
Output:-
Index 0 has value 10
Index 2 has value 30
Index 4 has value 50
---

*Common Mistakes:-

1. Forgetting to Unpack Values:"""
   
   items = ['a', 'b', 'c']
   for pair in enumerate(items):
       print(pair)  # Returns tuples
       
   """
   **Output**:
   ```
   (0, 'a')
   (1, 'b')
   (2, 'c')
   ```

   To unpack values:"""
   
   for i, value in enumerate(items):
       print(i, value)

""" 
*Performance Note:-
- enumerate() is efficient and works well with large iterables because it returns an iterator instead of creating a separate list of indices.

With its simplicity and versatility, enumerate() is an essential function in Python, especially for working with loops where index tracking is required.
"""