Learn Python control statements like if, elif, and else to manage program flow, essential for building robust AI and machine learning applications.

Python Control Statements

This document provides a comprehensive overview of control statements in Python, essential for managing the flow of execution within your programs.

2.1 Python `if`, `elif`, and `else` Statements

Conditional statements allow you to execute different blocks of code based on whether certain conditions are true or false.

The `if` Statement

The if statement executes a block of code only if a specified condition evaluates to True.

if condition:
    # Code to execute if condition is True
    statement1
    statement2

Example:

temperature = 25

if temperature > 30:
    print("It's a hot day!")

The `if-else` Statement

The if-else statement executes one block of code if the condition is True and another block if the condition is False.

if condition:
    # Code to execute if condition is True
    statement_if_true
else:
    # Code to execute if condition is False
    statement_if_false

Example:

score = 75

if score >= 60:
    print("You passed!")
else:
    print("You failed.")

The if-elif-else statement allows you to check multiple conditions in sequence. The first condition that evaluates to True will have its corresponding code block executed. If none of the if or elif conditions are True, the else block (if present) will be executed.

if condition1:
    # Code to execute if condition1 is True
    statement1
elif condition2:
    # Code to execute if condition1 is False and condition2 is True
    statement2
elif condition3:
    # Code to execute if condition1 and condition2 are False, and condition3 is True
    statement3
else:
    # Code to execute if all preceding conditions are False
    statement_else

Example:

grade = 'B'

if grade == 'A':
    print("Excellent!")
elif grade == 'B':
    print("Very Good!")
elif grade == 'C':
    print("Good.")
else:
    print("Needs Improvement.")

2.2 Python Loops

Loops are used to execute a block of code repeatedly. Python offers two primary types of loops: for loops and while loops.

2.3 Python `for` Loop

The for loop iterates over a sequence (like a list, tuple, string, or range) and executes a block of code for each item in the sequence.

for item in sequence:
    # Code to execute for each item
    statement1
    statement2

Example:

Iterating over a list:

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

Iterating using range():

# Prints numbers from 0 up to (but not including) 5
for i in range(5):
    print(i)

# Prints numbers from 2 up to (but not including) 7
for i in range(2, 7):
    print(i)

# Prints numbers from 0 up to 10, with a step of 2
for i in range(0, 10, 2):
    print(i)

2.4 Python `while` Loop

The while loop executes a block of code as long as a specified condition remains True. It's crucial to ensure that the condition eventually becomes False to avoid infinite loops.

while condition:
    # Code to execute as long as condition is True
    statement1
    statement2

Example:

count = 0
while count < 5:
    print(f"Count is: {count}")
    count += 1  # Increment count to eventually terminate the loop

2.5 Python `continue` Statement

The continue statement is used inside loops. When encountered, it skips the rest of the current iteration and moves to the next iteration of the loop.

Example:

for i in range(10):
    if i % 2 == 0:  # Skip even numbers
        continue
    print(i)

Output:

2.6 Python `break` Statement

The break statement is also used inside loops. When encountered, it immediately terminates the loop, and the program execution continues with the statement immediately following the loop.

Example:

numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for num in numbers:
    if num == 6:
        break  # Stop the loop when the number 6 is found
    print(num)

Output:

2.7 Python `pass` Statement

The pass statement is a null operation. It does nothing. It's used as a placeholder where a statement is syntactically required but you don't want any code to execute. This is often useful during program development when you plan to implement functionality later.

Example:

Using pass in an if statement:

x = 10

if x > 5:
    pass  # No action needed if x is greater than 5
else:
    print("x is not greater than 5")

Using pass in a function definition (to be implemented later):

def my_function():
    pass  # Function body will be added later

Using pass in a loop:

for i in range(5):
    pass # Do nothing in each iteration

Python Control Statements: Master Program Flow for AI

Python Control Statements

2.1 Python `if`, `elif`, and `else` Statements

The `if` Statement

The `if-else` Statement

The `if-elif-else` Statement

2.2 Python Loops

2.3 Python `for` Loop

2.4 Python `while` Loop

2.5 Python `continue` Statement

2.6 Python `break` Statement

2.7 Python `pass` Statement

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