# Lambda expression in Python Program to rearrange positive and negative numbers

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In this tutorial, we are going to write an anonymous function using lambda to rearrange positive and negative number in a list. We need the pick the negative numbers and then positive numbers from a list to create a new one.

## Algorithm

Let's see how to solve the problem step by step.

1. Initialize a list with negative and positive numbers.
2. Write a lambda expression the takes a list as an argument.
2.1. Iterate over the list and get negative numbers
2.2. Same for positive numbers
2.3. Combine both using concatination operator.
3. Return the resultant list.

Note - Use the list comprehension to get negative and positive numbers.

## Example

See the code below if you stuck at any point.

Live Demo

# initializing a list
arr = [3, 4, -2, -10, 23, 20, -44, 1, -23]
# lambda expression
rearrange_numbers = lambda arr: [x for x in arr if x < 0] + [x for x in arr if x >= 0]
# rearranging the arr
new_arr = rearrange_numbers(arr)
# printing the resultant array
print(new_arr)

## Output

If you execute the above program, then you will get the following output.

[-2, -10, -44, -23, 3, 4, 23, 20, 1]

## Conclusion

Lambda functions are great for a small operation that need to be perform many times in a program. If you have any doubts regarding the tutorial, mention them in the comment section.

Updated on 24-Apr-2020 12:34:21