- python built-in function reverse()
- the list slicing technique
- built-in python function reversed()
Table of Contents
Technique#01: By using the python built-in function reverse()
The reverse() method can reverse the items of the list object in-place. Using this method, we don’t need to create a new list because it copies the items inside the list, reverses all the items, and modifies the original list.
Syntax
list.reverse() It does not take any argument. Let’s have a look at an example.
Example: Using reverse() method
o_list = [16, 3, 75, 37]
print("original list : ", o_list)
o_list.reverse()
print("reversed list : ", o_list)
Output
We can see that the reverse() method reversed all the items in the list. If we print the list object directly on the reverse() method, it will return the special value None because it is modifying the original list, not creating a new list. Let’s examine it through an example.
o_list = [16, 3, 75, 37]
print("Directly calling list object : ", o_list.reverse())
Output
Here we can see we are getting None when we are calling the list object directly.
Technique#02: By Using the List Slicing Technique
This technique will create a copy of the list but not sorted in-place. That means it will occupy more space in memory.
Syntax
list[::-1] Let’s have a look at an example.
Example: Using Slicing Technique
o_list = [16, 3, 75, 37]
print("original list : ", o_list)
r_list = o_list[::-1]
print("reversed list : ", r_list)
Output
In this technique, we can call the object directly and get the reversed list. This technique will not return the special value None because it creates a copy of the original list. Let’s see this through an example.
o_list = [16, 3, 75, 37]
print("directly calling : ", o_list[::-1])
Output
Here we are getting the reversed list as a copy of the original list.
Technique#03: By Using the Built-in Python Function reversed()
This method will neither create a new copied list nor modify the original list. Instead, it will simply iterate the list items in reverse order.
Syntax
for items in reversed(list): Let’s have a look at an example.
Example: Using reversed() Method
o_list = [16, 3, 75, 37]
print("original list : ", o_list)
for item in reversed(o_list):
print("iterated item : ", item)
Output
As shown in the example above, the reversed() method gives us the reversed list by iterating through its items.