In python, we can retrieve the reverse of a number, a string, a list, and so on. The python reverse() function returns the sequence’s reversed order.
For example:
Input: str = I love coding in python
Output: str = python in coding love I
The syntax for the same is:
reversed(seq)
reversed() Parameters
The reversed function in python takes one argument as the input.
seq-this is the sequence that must be reversed.
Return value from reversed()
After implementing the reversed() in python, the reversed order of the given sequence will be returned.
Example 1: Using reversed() in the string, tuple, list, and range
We used the list() method to convert the iterators returned by reversed() to a list in our example.
Source Code
# for string
seqstring11 = 'Python'
print(list(reversed(seq_string)))
# for tuple
seqtuple11 = ('P', 'y', 't', 'h', 'o', 'n')
print(list(reversed(seq_tuple)))
# for range
seq_range = range(5, 9)
print(list(reversed(seq_range)))
# for list
seq_list = [1, 2, 4, 3, 5]
print(list(reversed(seq_list)))
Output
['n', 'o', 'h', 't', 'y', 'P']
['n', 'o', 'h', 't', 'y', 'P']
[8, 7, 6, 5]
[5, 3, 4, 2, 1]
Example 2: reversed() in custom objects
class Vowels:
vowels11 = ['a', 'e', 'i', 'o', 'u']
def __reversed__(self):
return reversed(self.vowels11)
v = Vowels()
print(list(reversed(v)))
Output
['u', 'o', 'i', 'e', 'a']
Is there a reverse function in Python?
Yes, the reversed() function allows us to reverse the order of items in a sequence. It takes a sequence as input and outputs an iterator.
For example:
The algorithm of the program is given below:
- Using the split() function of the string data type in Python, separate each word in a given string.
- Reverse the list of words in the list. After combining each word with a space using ” “, print the list’s words as a string using the join() in python.
Source Code:
def rev_sentence(sentence):
# First, break the string into words.
words1 = sentence.split(' ')
# We need to reverse the list
# using the split function and join
# them using the space function
reverse_sentence = ' '.join(reversed(words1))
#return reverse sentence from the joined string
if __name__ == "__main__":
input = 'geeks quiz practice code'
print (rev_sentence(input))
Output:
code practice quiz geeks
What is the reversed word in Python?
Example
#creating the string
strg1 = "I am an expert python programmer"
# splitting the string on space
words1 = strg1.split()
# reversing the words using reversed() function
words1 = list(reversed(words))
# joining the words and printing
print(" ".join(words1))
Output
programmer python an am I expert
How do you reverse a number in Python?
number = int(input("Enter the integer number: "))
# Initiate value to null
revs_number = 0
# Using the while loop, reverse the integer number.
while (number > 0):
# Logic applied for the program
remainder = number % 10
revs_number = (revs_number *10) + remainder
number = number // 10
# Display the result
print("The reverse number is : {}".format(revs_number))
Output:
Enter the integer number: 12345
The reverse number is: 54321
How do you reverse a list in Python 3?
In the Python programming language, we can reverse a list using three methods. The three methods are:
- Reverse the list using slicing
- Reverse the list using Reverse()
- Reverse the list using Reversed
Reversing the given list with the help of the slicing:
We declared our variable studentNames11 and then constructed a slice function to reverse the list in our code. This is a popular method of slicing lists. However, it is inefficient because it duplicates the list, which consumes memory. In addition, compared to other methods of reversing lists, this function can be a little more advanced.
Example:
studentNames11 = ["Hannah", "Imogen", "Lewis", "Peter", "Zayn", "Louis", "Harry"]
print(studentNames11[::-1])
Output:
["Harry", "Louis", "Zayn", "Peter", "Lewis", "Imogen", "Hannah"]
Example for reversing the program using the reverse()
The second method is to use the built-in reverse function (). To reverse the contents of a list object in-place, use the reverse() function. You will not be generating a new list as a result of this. Instead, we’ll make changes to the original list object.
Source Code:
list1 = ['physics', 'Biology', 'chemistry', 'maths']
list1.reverse()
print ("list now : ", list1)
Output
list now : ['maths', 'chemistry', 'Biology', 'physics']
Example: For reversing list using the reversed function
studentNames2 = ["Harry", "Ron", "Hermoine"]
for j in reversed(studentNames2):
print(j)
Output
"Hermoine"
"Ron"
"Harry"
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