Flow of Control in Python

Flow of control refers to the order in which individual statements, instructions, or functions are executed in a program. Python provides three basic types of control structures to determine the flow of execution: Sequential, Conditional, and Iterative.

1. Sequential Flow

Sequential flow is the default mode of execution in Python, where statements are executed one after another in the order they appear.

Characteristics:

• No decision-making or repetition.
• Each statement runs exactly once.

Example:

# Sequential Execution
print("Step 1: Start")
print("Step 2: Process")
print("Step 3: End")

Flowchart:

2. Conditional Flow

Conditional flow allows decision-making in a program. The flow of execution depends on whether a specified condition evaluates to True or False.

Types of Conditional Statements:

1. if Statement: Executes a block of code if the condition is true.
2. if-else Statement: Executes one block if the condition is true, another if it is false.
3. if-elif-else Statement: Tests multiple conditions.

Example:

# Conditional Flow
marks = 85
 
if marks >= 90:
    print("Grade: A+")
elif marks >= 75:
    print("Grade: A")
else:
    print("Grade: B")

Flowchart:

3. Iterative Flow (Loops)

Iteration allows the repetition of a block of code multiple times, as long as a specified condition holds true. Python supports two main types of loops:

1. for Loop: Used to iterate over a sequence (like a list or string).
2. while Loop: Repeats as long as a condition is true.

Example:

# Iterative Flow using a while loop
counter = 1
while counter <= 5:
    print("Count:", counter)
    counter += 1

Flowchart:

Combining All Flows

In real-world scenarios, programs often combine all three types of control flows:

• Sequential: For regular steps like initialization and cleanup.
• Conditional: For decision-making based on user inputs or results.
• Iteration: For repetitive tasks like processing data.

Example:

# Combining Sequential, Conditional, and Iterative Flows
print("Welcome to PythonForAll")
 
marks = int(input("Enter your marks: "))
 
if marks >= 50:
    print("You passed")
    for i in range(3):
        print("Congratulations")
else:
    print("Better luck next time")

Summary of Flow of Control