range() to a list in Python

In Python, the range() function is used to generate a sequence of numbers. However, it produces a range object, which is an iterable but not a list. If we need to manipulate or access the numbers as a list, we must explicitly convert the range object into a list. For example, given range(1, 5), we might want to convert it to [1, 2, 3, 4]. Let's explore various ways to achieve this.

Using list() Constructor

The simplest and most efficient way to convert a range object into a list is by using the list() constructor.

r = range(1, 5)

a = list(r)
print(a) 

[1, 2, 3, 4]

Explanation:

• list() constructor takes the range object as an input and converts it directly into a list.
• This method is fast, concise, and highly readable.

Using List Comprehension

List comprehension provides another efficient and Pythonic way to convert a range object into a list.

r = range(1, 5)

a = [x for x in r]
print(a) 

[1, 2, 3, 4]

Explanation:

• The comprehension iterates through each element in the range object.
• Each element is added to the new list, resulting in the complete conversion.

Using Unpacking Operator *

The unpacking operator * can unpack the elements of a range object directly into a list.

r = range(1, 5)

a = [*r]
print(a)

[1, 2, 3, 4]

Explanation:

• The * operator unpacks all elements of the range object.
• These elements are then stored in a new list.

Using for Loop (Manual Conversion)

A for loop can manually convert a range object into a list by iterating over its elements.

r = range(1, 5)
a = []

for x in r:
    a.append(x)

print(a)

[1, 2, 3, 4]

Explanation:

• An empty list is initialized.
• The loop iterates through the range object and appends each element to the list.

Using map()

map() function, combined with the identity function, can also convert a range object into a list.

r = range(1, 5)
a = list(map(lambda x: x, r))

print(a)

[1, 2, 3, 4]

Explanation:

• The map() function applies the identity function to each element of the range object.
• The resulting map object is converted into a list using the list() constructor.

Related Articles:

• Python range() function
• Python List methods
• List Comprehension in Python
• Python For Loops
• Python map() function