Control Flow

Definition: Control flow is the order in which individual statements, instructions, or function calls are executed or evaluated in a program. Python provides control flow tools like conditional statements, loops, and control statements to manage execution paths.

Control Flow

• Conditional Statements
  • if
  • if – else
  • if-elif-else
  • nested-if-else
• Iterative Statements
  • for loop
  • while loop
• Control Statements
  • break
  • continue
  • pass

✅ Conditional Statements

Used to make decisions based on conditions.

1. if Statement

Definition: Executes a block of code if a specified condition is true.

if condition:
    # code block

x = 10
if x > 5:
    print("x is greater than 5")

>2. if-else Statement

Definition: Executes one block if condition is true, another if false.

if condition:
    # true block
else:
    # false block

x = 3
if x > 5:
    print("x is greater than 5")
else:
    print("x is less than or equal to 5")

3. if-elif-else Statement

Definition: Multiple conditions can be tested in order.

if condition1:
    # block 1
elif condition2:
    # block 2
else:
    # default block

x = 7
if x > 10:
    print("x > 10")
elif x == 7:
    print("x is 7")
else:
    print("x is something else")

4. Nested if-else Statement

Definition: An if or else block can contain another if-else.

if condition1:
    if condition2:
        # nested block
    else:
        # nested else
else:
    # outer else

x = 10
if x > 5:
    if x < 15:
        print("x is between 5 and 15")
    else:
        print("x is 15 or more")
else:
    print("x is 5 or less")

🔁 Iterative Statements (Loops)

Used to repeat code execution.

1. for Loop

Definition: Iterates over a sequence (like list, string, or range).

for item in sequence:
    # loop block

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

2. while Loop

Definition: Repeats as long as the condition is true.

while condition:
    # loop block

x = 0
while x < 5:
    print(x)
    x += 1

⛔ Control Statements

Used to control loop execution.

1. break

Definition: Exits the loop entirely.

for i in range(10):
    if i == 5:
        break
    print(i)

2. continue

Definition: Skips the rest of the loop and moves to the next iteration.

for i in range(5):
    if i == 2:
        continue
    print(i)

3. pass

Definition: Placeholder; does nothing. Useful when the syntax requires a block.

for i in range(3):
    pass  # Placeholder for future code

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🧪 Practical Examples

✅ Example 1: Check Even or Odd

num = 7
if num % 2 == 0:
    print("Even")
else:
    print("Odd")

🔁 Example 2: for Loop Through a List

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

⛔ Example 3: Stop on Negative Number

numbers = [1, 3, -1, 5]
for num in numbers:
    if num < 0:
        break
    print(num)

🔁 Example 4: While Loop with Control

x = 0
while x < 5:
    if x == 3:
        x += 1
        continue
    print(x)
    x += 1

✅ Summary Table: Python Control Structures

Control Structure	Description	Key Use Case
if, elif, else	Executes code blocks based on specified conditions.	Implementing decision-making logic.
for loop	Iterates over a sequence (e.g., list, range, string).	Looping through known sequences or collections.
while loop	Repeats code while a condition remains true.	When the number of iterations is unknown.
break	Immediately exits the nearest enclosing loop.	Stopping a loop early when a condition is met.
continue	Skips the current iteration and moves to the next.	Skipping over specific iterations in a loop.
pass	Does nothing; used as a placeholder for future code.	Defining empty code blocks or stubs.