Control Flow constructs in Python

In Python, control flow refers to the order in which statements in a program are executed. That allows us to make decisions, repeat tasks, and handle errors. Here is a description of the main control flow constructs in Python:

Conditional Statement

The conditional statement allows a program to execute different blocks of code based on particular conditions.

if Statement: It executes a block of code if a condition is true.

python
📄
age = 18
if age >= 18:
    print("You are eligible to vote.")

if-else Statement: Provides an alternative block of code to execute if the condition is false.

python
📄
age = 16
if age >= 18:
    print("You are eligible to vote.")
else:
    print("You are not eligible to vote.")

if-elif-else Statement: It checks multiple conditions sequentially.

python
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score = 85
if score >= 90:
    print("Grade: A")
elif score >= 75:
    print("Grade: B")
else:
    print("Grade: C")

Loops

Loops are used to repeat the blocks of code multiple times as per the user's convenience.

for Loop: Iterates over a sequence (e.g., list, string, range).

python
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for i in range(1, 6):
    print(f"Number: {i}")

while Loop: Repeats till the condition is true.

python
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count = 0
while count < 5:
    print(f"Count: {count}")
    count += 1

Loop Control Statements

Loop control statements are used to change the flow of execution, such as to skip an iteration or stop the execution.

Break statements: Programmatically exit from a loop.

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

continue: Skips the current iteration and moves to the next.

python
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for num in range(10):
    if num % 2 == 0:
        continue
    print(num)

pass: Acts as a placeholder for future code.

python
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for num in range(5):
    pass  # Does nothing but prevent syntax errors

Exception Handling

Exception handling is a programming concept that manages errors and unexpected events that occur during program execution. The goal of exception handling is to easily deal with errors without crashing the program.

try-except block: It handles exceptions (errors) that occur during program execution.

python
📄
try:
    x = 10 / 0
except ZeroDivisionError:
    print("Cannot divide by zero")

try-except-else block: It executes code if no exceptions occur.

python
📄
try:
    x = 10 / 2
except ZeroDivisionError:
    print("Cannot divide by zero")
else:
    print("Division successful")

try-except-finally block: It executes code regardless of whether an exception occurred.

python
📄
try:
    x = 10 / 2
except ZeroDivisionError:
    print("Cannot divide by zero")
finally:
    print("This block always executes")

Match Statement (Python 3.10 and above)

A match statement takes an expression and compares its value to successive patterns given as one or more case blocks.

python
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match x:
    case 1:
        print("x is 1")
    case 2:
        print("x is 2")
    case _:
        print("x is something else")

Conclusion

Control flow in Python dictates the order in which your code is executed. It lets you create programs that are operational and interactive enough to treat different possible situations and make decisions based on conditions.