Indentation in Python

In Python, indentation is used to define a block of code. The standard indentation is 4 spaces.

# Example
x = 10
if x > 5:
    print('x is greater than 5')

If you use a different number of spaces or tabs, Python will raise an IndentationError.

# Example
x = 10
if x > 5:
    print('x is greater than 5') # IndentationError

Control Flow

Conditional Statements

Conditional statements are used to execute a block of code based on a condition.

if Statements

The if statement is the most basic form of a conditional statement. It is used to execute a block of code if a condition is true.

# Syntax
if condition:
    # code block

The if statement is followed by a condition. If the condition is true, the code block is executed. If the condition is false, the code block is skipped.

# Example
x = 10
if x > 5:
    print('x is greater than 5')

if-else Statements

The if statement can be followed by an else statement. The else statement is used to execute a block of code if the condition is false.

# Syntax
if condition:
    # code block
else:
    # code block

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

if-elif-else Statements

The if statement can be followed by one or more elif (else if) statements. The elif statement is used to check additional conditions if the previous conditions are false.

# Syntax
if condition:
    # code block
elif condition:
    # code block
else:
    # code block

# Example
x = 3
if x > 5:
    print('x is greater than 5')
elif x == 5:
    print('x is equal to 5')
else:
    print('x is less than 5')

Nested if Statements

if statements can be nested inside other if statements. This is useful when you want to check for additional conditions.

# Example
x = 10
y = 5
if x > 5:
    if y > 5:
        print('x and y are greater than 5')
    else:
        print('x is greater than 5, but y is less than or equal to 5')
else:
    print('x is less than or equal to 5')

Loops

Loops are used to execute a block of code multiple times.

for Loops

The for loop is used to iterate over a sequence (e.g., a list, tuple, string).

# Syntax
for item in sequence:
    # code block

# Example
fruits = ['apple', 'banana', 'cherry']
for fruit in fruits:
    print(fruit)

while Loops

The while loop is used to execute a block of code as long as a condition is true.

# Syntax
while condition:
    # code block

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

Nested Loops

Loops can be nested inside other loops. This is useful when you want to iterate over multiple sequences.

# Example
adj = ['red', 'big', 'tasty']
fruits = ['apple', 'banana', 'cherry']
for a in adj:
    for f in fruits:
        print(a, f)

Exercises

1. Write a program to check if a number is positive, negative, or zero.
2. Write a program to find the sum of all numbers in a list.
3. Write a program to find the factorial of a number.
4. Write a program to print the Fibonacci series up to n terms.
5. Write a program to check if a number is prime or not.
6. Write a program to check if a string is a palindrome.