Loops

Introduction

Loops in Python execute a statement or a set of statements repeatedly. The statement or the set of statements inside the loop has to be indented. The loop iterates the block sequentially until the condition is false.

for loop

This loop executes a sequence of statements for all the given items in the list or array. The "for loop" exits the loop once the iteration of the values in the list is over. The range(a, b) of Python includes the number between a and b, while b is exclusive. So range(0, 10) includes numbers 0 to 9.

for i in range(0, 10):
    print(i)

Output:

0
1
2
3
4
5
6
7
8
9

While loop

This loop executes the code until the given condition for the execution is false. Here the syntax differs from the C, but the logic remains the same.

i = 0
while i < 5:
    print(i)
    i = i + 1

Output:

0
1
2
3
4

Nested loop

Nested loops are loops inside other loops. The inner loop is executed once for each iteration of the outer loop. We can create tables or patterns by using nested loops.

for i in range(1, 3):
  for j in range(3, 6):
    print(i, j)

Output:

1 3
1 4
1 5
2 3
2 4
2 5

Breaking the loop

• Break statement - Break out of the loop by break keyword; this causes the process to move out of the loop and execute the next statement following the loop code.

search_name = input("Enter a name for searching: ")
found = False
name_list = ["Mary", "John", "Peter", "kelly"]

for name in name_list:
    if name == search_name:
       found = True
       break;

print("Found") if found else print("Not found")

Output:

Enter a name for searching: John
Found

• Continue statement - It causes the loop to skip the remainder of its body and immediately retest its condition before reiterating.

no_space_string = ""

for char in "apple bee":
    if char == " ": #skip the space symbol
       continue;
    no_space_string += char

print(no_space_string)

Output:

applebee