check if all elements in a list are positive

Python – Check If All Elements in List are Positive

In this tutorial, we will look at how to check if all the elements in a list are positive (greater than 0) or not in Python with the help of some examples.

How to check if all the list items are positive?

You can use the Python built-in all() function to check if all the elements in a list are positive or not by comparing each value in the list with 0.

check if all elements in a list are positive

The all() function takes in an iterable as an argument and returns True if all the values in the iterable are truthy (represent True in a boolean context).

So, to check if all the values in a given list are positive or not, use the all() function to check if all the values are greater than 0. The following is the syntax –

# check if all the list values are positive
all(val > 0 for val in ls)

It returns True if all the values in the list are greater than 0.

Note that there are other methods as well that you can use to check if all list values are positive or not. For example –

  • Iterate through the list and keep a count of values that are greater than 0. If this count is the same as the length of the list, you can say that all values are positive.

Examples

Let’s now look at some examples of using the above methods. First, we will create a few lists that we’ll use to demonstrate the methods.

# list with all positive values
ls1 = [1, 2, 3, 4, 5, 5]
# list with positive, negative and zero values
ls2 = [0, 1, 2, 3, -4, 5, -5]
# empty list
ls3 = []

# display the lists
print(ls1)
print(ls2)
print(ls3)

Output:

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[1, 2, 3, 4, 5, 5]
[0, 1, 2, 3, -4, 5, -5]
[]

Here, we created three lists – ls1, ls2, and ls3. The list ls1 contains only positive values as its elements. The list ls2 has repeated values but not all values are greater than zero and the list ls3 is empty (it does not contain any elements).

Example 1 – Check if all the list elements are positive using all()

The idea here is to use the all() function to check if each list element is positive (greater than 0).

You can use a list comprehension to create a list of boolean values – whether a list element is greater than 0 or not and then pass this resulting list as an argument to the all() function.

Let’s apply this to the lists ls1 and ls2 created above.

# check if all list values are positive
print(all([val > 0 for val in ls1]))
print(all([val > 0 for val in ls2]))

Output:

True
False

We get True for ls1 and False for ls2.

If you apply this method to an empty list, you’ll get True as the output.

all([val > 0 for val in ls3])

Output:

True

Note that the all() takes an iterable as an argument, you can directly use an iterator (without using a list comprehension).

# check if all list values are positive
print(all(val > 0 for val in ls1))
print(all(val > 0 for val in ls2))
print(all(val > 0 for val in ls3))

Output:

True
False
True

We get the same results as above.

Example 2 – Check if all list elements are positive using a for loop

The idea, here, is to iterate through the list and keep a count of positive values in the list. If the resulting count is the same as the length of the list, we can say that all the values in the list are positive.

def all_list_elements_positive(ls):
    count = 0
    for val in ls:
        if val > 0:
            count += 1
    return count == len(ls)

# check if all list values are positive
print(all_list_elements_positive(ls1))
print(all_list_elements_positive(ls2))
print(all_list_elements_positive(ls3))

Output:

True
False
True

We get True for ls1 and False for ls2. Note that here we get True for an empty list.

Summary

In this tutorial, we looked at some different methods to check if all the values in a list are positive or not. The following are the different methods covered –

  • Use the Python built-in all() function to check if each list element is greater than zero.
  • Iterate through the list elements and track the count of values that are greater than zero and then compare this count with the length of the list.

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Author

  • Piyush Raj

    Piyush is a data professional passionate about using data to understand things better and make informed decisions. He has experience working as a Data Scientist in the consulting domain and holds an engineering degree from IIT Roorkee. His hobbies include watching cricket, reading, and working on side projects.

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