Python Tutorial - For Loop

Jinku Hu Mar 21, 2022 Feb 07, 2018 Python Python Loop
  1. Python for Loop
  2. the Range() Functions
  3. for Loop With else
Python Tutorial - For Loop

The Python for loop is used to iterate over the elements of a sequence or other iterable objects.

Python for Loop

Below is the syntax of for loop in Python:

for val in sequence:
    block of statements

Here val is the variable that is the value of the elements or items of the sequence in each iteration. The loop is terminated after val reaches the last item of the sequence.

The body of the for loop is indicated by indentation and not curly braces { }. The first unindented line will be the end of the for loop.

for Loop Example

x = {1, 2, 3, 4, 5, 6, 7, 8, 9}
sum = 0
for i in x:
    sum = sum + i
print("Sum of elements of x =", sum)
Sum of elements of x = 45

the Range() Functions

A sequence of numbers can be generated using the range() function. The range starts from 0 if no start number is assigned. When you write range(10), it will generate numbers from 0 to 9.

The following is the syntax of range() function:

range(start, stop, step size)

start and stop are the starting and ending points and step size describes the interval between each item.

The range() function actually defines a range and not tells individual items. If you want to see each item in a range you can use list() function:

print(range(10))		#OUTPUT: range(0, 10)
print(list(range(10)))	#OUTPUT: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

Range() With for Loop

In the following program, range() function iterates through a sequence using for loop and through indexing that is by using the len() function.

l = ['Python', 'Java', 'C', 'Kotlin']
for i in range(len(l)):
    print("Programming Language is:", l[i])
Programming Language is: Python
Programming Language is: Java
Programming Language is: C
Programming Languages is: Kotlin

for Loop With else

You can use else with for loop to break through the loop if there is no break statement. else part will be executed after the items in a sequence are ended. else contains a body in which you can perform tasks which will be executed when the sequence has no items left.

l = [1, 2, 3, 4, 5]
for i in l:
    print("Items in list:", i)
else:
    print("List is ended")
Items in list: 1
Items in list: 2
Items in list: 3
Items in list: 4
Items in list: 5
List is ended

When there are no items left in list l, the else part will be executed and the message is printed.

Author: Jinku Hu
Jinku Hu avatar Jinku Hu avatar

Founder of DelftStack.com. Jinku has worked in the robotics and automotive industries for over 8 years. He sharpened his coding skills when he needed to do the automatic testing, data collection from remote servers and report creation from the endurance test. He is from an electrical/electronics engineering background but has expanded his interest to embedded electronics, embedded programming and front-/back-end programming.

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