# Python reverse number – Write a Program to Reverse a Number in Python | Reverse Digits or Integers

Python reverse number: Given a number, thee task is to reverse the given number in Python.

### Examples:

Example1:

Input:

number=12345

Output:

The reversed number = 54321

Explanation:

After reversing the number we get 54321

Example2:

Input:

number=7341

Output:

The reversed number = 1437

Example3:

Input:

number=9840

Output:

The reversed number = 489

Explanation:

Here the reversed number is 0489 we neglect the leading zero so the reversed number is 489

## Reverse the given Number in Python

Reverse a number python: There are several ways to reverse the given number in python some of them are:

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### Method #1:Using while loop

Algorithm:

• Scan the given number
• Set the variable reverse_number to 0.
• Loop while number > 0 Loop while number > 0
• Multiply reverse_number by 10 and add the remainder to reverse_number like below
• reverse_number = (reverse_number * 10) + remainder
• Divide the given number by 10 to remove the last digit.
• Print the reversed number

Below is the implemenatation:

# given number
given_num = 12345

# Take a variable reverse_number and initialize it to null
reverse_number = 0

# using while loop to reverse the given number

while (given_num > 0):
# implementing the algorithm
# getting the last digit
remainder = given_num % 10
reverse_number = (reverse_number * 10) + remainder
given_num = given_num // 10

# Display the result
print("The reversed number =", reverse_number)


Output:

The reversed number = 54321

### Method #2: Using for loop and string concatenation

Approach:

• Scan the given number.
• Take a empty string say revstring.
• Convert the given number to string using str() function.
• Traverse every character of the string using for loop in reverse order using range function.
• Add each character to revstring using string concatenation.
• Print the revstring.

Below is the implementation:

1)For numbers without trailing zeroes

# given number
given_num = 12345
# taking empty string
reverse_string = ""
# Convert the given_num to string using str
strnum = str(given_num)
# calculating the length of string
length = len(strnum)
# Traverse the strnum string in reverse order using for loop range function
for index in range(length-1, -1, -1):
# add the character to reverse_string using string concatenation
reverse_string = reverse_string+strnum[index]
# print the result
print("The reversed number =", reverse_string)


Output:

The reversed number = 54321

Note:

Here it gives the correct result as their are no trailing zeroes

Let us consider a case where the given number contains trailing zeroes .

EX: 9840

How to reverse a number in python: The above algorithm gives the output

The reversed number = 0489

Here it also prints the leading zeroes so to avoid this the solution is given below.

Solution:

After getting the reversed string convert the string to integer using int() function which removes the leading zeroes

as below.

2)For numbers with trailing zeroes

# given number
given_num = 9840
# taking empty string
reverse_string = ""
# Convert the given_num to string using str
strnum = str(given_num)
# calculating the length of string
length = len(strnum)
# Traverse the strnum string in reverse order using for loop range function
for index in range(length-1, -1, -1):
# add the character to reverse_string using string concatenation
reverse_string = reverse_string+strnum[index]
# converting the string to integer using int() function
reverse_number = int(reverse_string)
# print the result
print("The reversed number =", reverse_number)


Output:

The reversed number = 489

### Method #3:Using Slicing

Approach:

• Scan the given number.
• Convert the given number to string using str() function.
• Reverse the string using slicing
• Convert this reversed string to integer to avoid leading zeros as mentioned in method #2.
• Print the reversed string.

Below is the implementation:

# given number
given_num = 9840
# Convert the given_num to string using str
strnum = str(given_num)
# calculating the length of string
length = len(strnum)
# Reversing the string using slicing
reverse_string = strnum[len(strnum)::-1]
# converting the string to integer using int() function
reverse_number = int(reverse_string)
# print the result
print("The reversed number =", reverse_number)


Output:

The reversed number = 489

### Method #4:Using list  and join functions

Approach:

• Scan the given number.
• Convert the given number to string using str() function.
• Convert this string to list of digits using list() function.
• Reverse the list using reverse() function
• Join the list using join() function to get reversed string.
• Convert this reversed string to integer to avoid leading zeros as mentioned in method #2.
• Print the reversed string.

Below is the implementation:

# given number
given_num = 9840
# Convert the given_num to string using str
strnum = str(given_num)
# converting to list of digits
numberslist = list(strnum)
# reverse the list and
numberslist.reverse()
# convert this list to string using join
reverse_string = ''.join(numberslist)
# converting the string to integer using int() function
reverse_number = int(reverse_string)
# print the result
print("The reversed number =", reverse_number)


Output:

The reversed number = 489

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