Merge pull request #417 from Adez017/Adez017/python

added loops page in docs

Author: sanjay-kv

docs/python/python-loops.md

@@ -0,0 +1,305 @@
+---
+id: python-loops
+title: Loops in Python
+sidebar_label: Loops in Python
+sidebar_position: 10
+tags:
+  - Python
+  - Loops
+  - for loop
+  - while loop
+  - Control Flow
+  - Iteration
+  - Python Syntax
+---
+
+# Loops in Python
+
+Loops in Python allow you to execute a block of code repeatedly. They are essential for automating repetitive tasks and processing collections of data efficiently.
+
+## The `for` Loop
+
+The `for` loop is used to iterate over a sequence (like a list, tuple, string, or range).
+
+**Syntax:**
+
+```python
+for variable in sequence:
+    # block of code
+```
+
+**Example:**
+
+```python
+fruits = ["apple", "banana", "cherry"]
+for fruit in fruits:
+    print(fruit)
+```
+
+**Output:**
+```
+apple
+banana
+cherry
+```
+
+## The `range()` Function
+
+The `range()` function generates a sequence of numbers, commonly used with `for` loops.
+
+```python
+# Print numbers 0 to 4
+for i in range(5):
+    print(i)
+
+# Print numbers 2 to 6
+for i in range(2, 7):
+    print(i)
+
+# Print even numbers from 0 to 8
+for i in range(0, 10, 2):
+    print(i)
+```
+
+**Output:**
+```
+0
+1
+2
+3
+4
+```
+
+## The `while` Loop
+
+The `while` loop continues executing as long as a condition is **True**.
+
+**Syntax:**
+
+```python
+while condition:
+    # block of code
+```
+
+**Example:**
+
+```python
+count = 1
+while count <= 5:
+    print(f"Count: {count}")
+    count += 1
+```
+
+**Output:**
+```
+Count: 1
+Count: 2
+Count: 3
+Count: 4
+Count: 5
+```
+
+## Loop Control Statements
+
+### The `break` Statement
+
+`break` exits the loop immediately.
+
+```python
+for i in range(10):
+    if i == 5:
+        break
+    print(i)
+```
+
+**Output:**
+```
+0
+1
+2
+3
+4
+```
+
+### The `continue` Statement
+
+`continue` skips the current iteration and moves to the next one.
+
+```python
+for i in range(5):
+    if i == 2:
+        continue
+    print(i)
+```
+
+**Output:**
+```
+0
+1
+3
+4
+```
+
+### The `pass` Statement
+
+`pass` is a placeholder that does nothing. Useful when you need syntactically correct code but no action.
+
+```python
+for i in range(3):
+    if i == 1:
+        pass  # Do nothing for i == 1
+    else:
+        print(i)
+```
+
+## Nested Loops
+
+You can place one loop inside another loop.
+
+```python
+# Multiplication table
+for i in range(1, 4):
+    for j in range(1, 4):
+        print(f"{i} x {j} = {i * j}")
+    print()  # Empty line after each row
+```
+
+**Output:**
+```
+1 x 1 = 1
+1 x 2 = 2
+1 x 3 = 3
+
+2 x 1 = 2
+2 x 2 = 4
+2 x 3 = 6
+
+3 x 1 = 3
+3 x 2 = 6
+3 x 3 = 9
+```
+
+## Looping Through Different Data Types
+
+### Strings
+
+```python
+word = "Python"
+for letter in word:
+    print(letter)
+```
+
+### Dictionaries
+
+```python
+student = {"name": "Alice", "age": 20, "grade": "A"}
+
+# Loop through keys
+for key in student:
+    print(key)
+
+# Loop through values
+for value in student.values():
+    print(value)
+
+# Loop through key-value pairs
+for key, value in student.items():
+    print(f"{key}: {value}")
+```
+
+### Lists with Index
+
+```python
+colors = ["red", "green", "blue"]
+
+# Using enumerate() to get index and value
+for index, color in enumerate(colors):
+    print(f"{index}: {color}")
+```
+
+**Output:**
+```
+0: red
+1: green
+2: blue
+```
+
+## The `else` Clause in Loops
+
+Loops can have an `else` clause that executes when the loop completes normally (not broken by `break`).
+
+```python
+# With for loop
+for i in range(3):
+    print(i)
+else:
+    print("Loop completed!")
+
+# With while loop
+count = 0
+while count < 3:
+    print(count)
+    count += 1
+else:
+    print("While loop finished!")
+```
+
+## Common Loop Patterns
+
+### Counting Pattern
+
+```python
+# Count occurrences
+text = "hello world"
+count = 0
+for char in text:
+    if char == 'l':
+        count += 1
+print(f"Letter 'l' appears {count} times")
+```
+
+### Accumulation Pattern
+
+```python
+# Sum of numbers
+numbers = [1, 2, 3, 4, 5]
+total = 0
+for num in numbers:
+    total += num
+print(f"Sum: {total}")
+```
+
+### Finding Pattern
+
+```python
+# Find first even number
+numbers = [1, 3, 5, 8, 9, 10]
+for num in numbers:
+    if num % 2 == 0:
+        print(f"First even number: {num}")
+        break
+```
+
+## Best Practices
+
+1. **Use `for` loops** when you know the number of iterations
+2. **Use `while` loops** when the condition determines when to stop
+3. **Avoid infinite loops** by ensuring the condition eventually becomes `False`
+4. **Use meaningful variable names** in loops
+5. **Consider list comprehensions** for simple transformations
+
+## Summary Table
+
+| Loop Type               | Use Case                                    |
+|------------------------|---------------------------------------------|
+| `for` loop             | Iterating over sequences (lists, strings)  |
+| `while` loop           | Repeating until a condition is met         |
+| `break`                | Exit loop immediately                       |
+| `continue`             | Skip current iteration                      |
+| `pass`                 | Placeholder for empty loop body             |
+| Nested loops           | Working with multi-dimensional data         |
+| List comprehensions    | Creating lists with concise syntax          |
+
+## Conclusion
+
+Loops are fundamental to programming in Python. Whether you're processing data, automating tasks, or building complex algorithms, mastering `for` and `while` loops will make your code more efficient and powerful. Practice with different data types and loop patterns to become proficient in using loops effectively.