5.2 For loop

Learning objectives

By the end of this section you should be able to

• Explain the for loop construct.
• Use a for loop to implement repeating tasks.

For loop

In Python, a container can be a range of numbers, a string of characters, or a list of values. To access objects within a container, an iterative loop can be designed to retrieve objects one at a time. A for loop iterates over all elements in a container. Ex: Iterating over a class roster and printing students' names.

    str_var = "A string"

    count = 0
    for c in str_var:
      count += 1

    print(count)

str_var = "A string"

count = 0
for c in str_var:
  count += 1
  # New line
  print(c, end = '*')

print(count)

Range()

function in for loop

A for loop can be used for iteration and counting. The range() function is a common approach for implementing counting in a for loop. A range() function generates a sequence of integers between the two numbers given a step size. This integer sequence is inclusive of the start and exclusive of the end of the sequence. The range() function can take up to three input values. Examples are provided in the table below.

# For loop condition using 
# range() function to print 
# all multiples of 5 less than 50
for i in range(0, 50, 5):
  print(i)

# While loop implementation of printing 
# multiples of 5 less than 50
    
# Initialization
i = 0
# Limiting the range to be less than 50
while i < 50:
    print(i)
    i+=5