Python – Remove Negative Elements in List

Sometimes, while working with Python lists, we can have a problem in which we need to remove all the negative elements from list. This kind of problem can have application in many domains such as school programming and web development. Let’s discuss certain ways in which this task can be performed.

Input : test_list = [6, 4, 3] Output : [6, 4, 3] Input : test_list = [-6, -4] Output : []

Method #1 : Using list comprehension The combination of above functions can be used to solve this problem. In this, we perform the task of removing negative elements by iteration in one liner using list comprehension 

Python3

# Python3 code to demonstrate working of
# Remove Negative Elements in List
# Using list comprehension

# initializing list
test_list = [5, 6, -3, -8, 9, 11, -12, 2]

# printing original list
print("The original list is : " + str(test_list))

# Remove Negative Elements in List
# Using list comprehension
res = [ele for ele in test_list if ele > 0]

# printing result
print("List after filtering : " + str(res))

Output : 

The original list is : [5, 6, -3, -8, 9, 11, -12, 2]
List after filtering : [5, 6, 9, 11, 2]

Method #2 : Using filter() + lambda The combination of above functions can also offer an alternative to this problem. In this, we extend logic of retaining positive formed using lambda function and extended using filter(). 

Python3

# Python3 code to demonstrate working of
# Remove Negative Elements in List
# Using filter() + lambda

# initializing list
test_list = [5, 6, -3, -8, 9, 11, -12, 2]

# printing original list
print("The original list is : " + str(test_list))

# Remove Negative Elements in List
# Using filter() + lambda
res = list(filter(lambda x : x > 0, test_list))

# printing result
print("List after filtering : " + str(res))

Output : 

The original list is : [5, 6, -3, -8, 9, 11, -12, 2]
List after filtering : [5, 6, 9, 11, 2]

Method #3: Using list(),map(),startswith() methods

Python3

# Python3 code to demonstrate working of
# Remove Negative Elements in List

# initializing list
test_list = [5, 6, -3, -8, 9, 11, -12, 2,0]

# printing original list
print("The original list is : " + str(test_list))

# Remove Negative Elements in List
x=list(map(str,test_list))
res=[]
for i in range(0,len(x)):
    if(not x[i].startswith("-") and x[i]!="0"):
        res.append(test_list[i])

# printing result
print("List after filtering : " + str(res))

Output

The original list is : [5, 6, -3, -8, 9, 11, -12, 2]
List after filtering : [5, 6, 9, 11, 2]