Python Control Flow Statements and Loops

Conditional Statements (if-elif-else)

Conditional statements are fundamental for controlling the flow of your program. They allow you to execute different code blocks based on conditions.

x = 10

if x > 10:
    print("x is greater than 10")
elif x < 10:
    print("x is less than 10")
else:
    print("x is equal to 10")

if: The if statement evaluates a condition (in this case, x > 10) and executes the indented block of code underneath it if the condition is True.

elif (else if): The elif statement is used for additional conditions to check if the initial if condition is False. You can have multiple elif clauses.

else: The else statement is executed when none of the preceding conditions is True. It's optional, and you can have only one else statement at the end.

Advanced Example

temperature = 25
if temperature > 30:
    print("It's hot outside.")
elif 20 <= temperature <= 30:
    print("It's a pleasant day.")
else:
    print("It's cold outside.")

For Loop

A for loop is used to iterate over a sequence of items. Python's for loop is incredibly versatile, as it can iterate over various types of sequences.

fruits = ["apple", "banana", "cherry"]

for fruit in fruits:
    print(f"I like {fruit}")

Iterating over a Range 

The range() function generates a sequence of numbers that can be used with a for loop. It's often used to iterate a specific number of times.

for i in range(5):  # Range from 0 to 4
    print(i)

Looping with a Step

You can specify a step value when using range(). This allows you to iterate with a specific increment.

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

Advanced Example

words = ["apple", "banana", "cherry"]
for word in words:
    if "a" in word:
        print(f"The word '{word}' contains 'a'.")

While Loop

A while loop is used when you want to repeat a block of code as long as a specified condition is True. It's often used for tasks where the number of iterations is unknown in advance.

count = 0

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

Using break

The break statement is used to exit a loop prematurely when a certain condition is met.

while True:
    user_input = input("Enter 'q' to quit: ")
    if user_input == 'q':
        break
    print(f"You entered: {user_input}")

Using continue

The continue statement is used to skip the current iteration of the loop and move to the next one.

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

Advanced Example

balance = 1000
interest_rate = 0.05
years = 0

while balance < 2000:
    balance += balance * interest_rate
    years += 1

print(f"It will take {years} years to double your balance.")

These advanced examples demonstrate how control structures and loops can be used for complex decision-making and iterative processes in Python. Control structures and loops are essential for writing efficient and flexible programs.