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How To Print Negative Numbers Of A List In Python?

In this article, we will learn to write a python program to find and print all the negative numbers present in the python list.

We know that the list is an ordered set of values enclosed in square brackets [ ]. We can access the elements in the list by their particular index. A number that is less than zero is known as a negative number. Negative numbers are written with the hyphen(-) sign in front of them.

Sample Input and Output Examples:

Input: list1 = [1,-5,7,-3,-6,4]
output: -5,-3,-6
​
Input: list2 = [-15,20,22,-33,4]
output:-15,-33

We will use the following approaches to solve this problem.

  1. for loop

  2. list comprehension

  3. lambda expression

Let's understand the topic with the help of some simple examples.

Find Negative Elements of a List using for loop in Python

Here, we will use for loop to traverse each element of the list and fetch the negative elements. An algorithm is given below.

Algorithm

Step 1: Start

Step 2: Create a list of numbers

Step 3: Start a for loop

Step 4: Add an if condition to check the negative element

Step 5: If the condition true, print that number

Step 6: No output

Step 7: End

Look at the program below to understand the implementation of the above-mentioned algorithm.

# Python program to print negative numbers in a list
# list of numbers
list1 = [1, -5, 7, -3, -6, 4]

# iterating each number in the list
for num in list1:

 # checking the condition
 if num < 0:
    print(num)

Output:

-5

-3

-6

Here, we used another approach to solve the problem, we have taken an input of elements of the list from the user and then by using python built-in function append(), we have added all the elements to the list. And then to print negative numbers, we have done traversing and checking with the help of for loop and if statement.

# Python program to print negative numbers in a list
​
# Empty list for storing input elements
list1 = []
​
# Size of the list
n = int(input("Enter size of list: "))
​
# Create a for loop
for i in range(0, n):
    # Take elements of list from user
    ele_input = int(input(f"Enter the element {i+1}: "))
    # Append all the element in the list1
    list1.append(ele_input)
​
print("Negative numbers in", list1, "are: ")
​
# iterating each number in list
for i in list1:
    # checking condition
    if i < 0:
        print(i, end=" ")

Output:

Enter size of list: 5
Enter the element 1: 23
Enter the element 2: -34
Enter the element 3: -53
Enter the element 4: 32
Enter the element 5: -54
Negative numbers in [23, -34, -53, 32, -54] are:
-34 -53 -54

Find Negative Elements of a List using list comprehension in Python

In this approach, we are going to use the list comprehension method to print negative numbers in a list. List comprehension is an easy and elegant way to define and create a list in python. An algorithm is given below.

Algorithm

Step 1: Start

Step 2: Create a list of numbers by user input

Step 3: Apply list comprehension to find the negative numbers

Step 4: Provide if condition in the list comprehension to check whether the element is negative

Step 5: If the number satisfies the condition, store it in a new list

Step 6: Print the new list

Step 7: End

Here, we have created a list of numbers and then by using the above-mentioned algorithm, we printed all the negative numbers present in that list.

# Python program to print negative numbers in a list
​
# list of numbers
list1 = [1, -5, 7, -3, -6, 4]
​
# using list comprehension
negative_num = [num for num in list1 if num < 0]
print("Negative numbers in the list: ", *negative_num)

Output:

Negative numbers in the list: -5 -3 -6

Find Negative Elements of a List Using lambda expression

Here, we will use the lambda function to find negative elements of a list. In python, the lambda function is an anonymous function that means the function without a name. An algorithm is given below.

Algorithm 

Step 1: Start

Step 1: Create a list of numbers

Step 2: Create a lambda expression to print negative elements

Step 3: Provide condition the lambda expression to check whether the list contains any negative number

Step 4: If the number satisfies the condition, store it in a new list

Step 5: Print the new list

Step 6: End

Here, we have created a list of numbers and then by using the above-mentioned algorithm, we printed all the negative numbers present in that list. See the Python code below.

# Python program to print negative numbers in a list
​
# list of numbers
list1 = [1, -5, 7, -3, -6, 4]
​
# print negative numbers using lambda expression.
negative_num = list(filter(lambda x: (x < 0), list1))
​
print("Negative numbers in the list: ", *negative_num)

Output:

Negative numbers in the list: -5 -3 -6