Iterative Statements in Python

In programming, it's common to need to perform the same operation multiple times on different inputs or data structures. Iterative statements provide a way to automate this process by repeating a block of code until a certain condition is met. In Python, there are two types of iterative statements: for loops and while loops .

For Loops

A for loop is used to iterate over a sequence of elements, such as a list or a string. The general syntax of a for loop in Python is:

for element in sequence:
    # code to execute on each iteration

Here, element is a variable that takes on the value of each element in the sequence, one at a time, and sequence is the sequence of elements to iterate over. The code inside the loop is executed once for each element in the sequence.

For example, here's a for loop that iterates over a list of numbers and prints each one:

numbers = [1, 2, 3, 4, 5]

for num in numbers:
    print(num)

This will output:

1
2
3
4
5

You can also use a for loop to iterate over the characters in a string:

my_string = "Hello, world!"

for char in my_string:
    print(char)

This will output:

H
e
l
l
o
,
 
w
o
r
l
d
!

You can also use the built-in range() function to generate a sequence of numbers to iterate over:

for i in range(10):
    print(i)

This will output the numbers 0 through 9.

While Loops

A while loop is used to repeat a block of code while a certain condition is true. The general syntax of a while loop in Python is:

while condition:
    # code to execute on each iteration

Here, condition is an expression that evaluates to either True or False . The code inside the loop is executed repeatedly as long as the condition is true.

For example, here's a while loop that counts up from 1 to 10:

i = 1

while i <= 10:
    print(i)
    i += 1

This will output the numbers 1 through 10.

It's important to be careful when using a while loop, as it's possible to create an infinite loop if the condition never becomes false. For example, this code:

while True:
    print("Hello, world!")

will print "Hello, world!" forever, because the condition is always true. If you accidentally create an infinite loop, you can interrupt the program by pressing Ctrl+C in the terminal.

Break and Continue Statements

Both for loops and while loops can be controlled using break and continue statements.

A break statement is used to exit a loop prematurely, regardless of whether the loop condition has been met. For example, in this code:

numbers = [1, 2, 3, 4, 5]

for num in numbers:
    if num == 3:
        break
    print(num)

the loop will exit after printing the numbers 1 and 2, because the break statement is executed when num is 3.

A continue statement is used to skip over an iteration of the loop and move on to the next one. For example, in this code:

numbers = [1, 2, 3, 4, 5]

for num in numbers:
    if num % 2 == 0:
        continue
    print(num)

only the odd numbers (1, 3, and 5) will be printed, because the continue statement is executed when num is even.

Conclusion

Iterative statements are a fundamental concept in programming, and Python provides two powerful types of loops: for loops and while loops. You can use these loops to automate repetitive tasks and process large data sets. By combining loops with control statements like break and continue , you can create complex algorithms and solve a wide variety of programming problems.