Python – Check if a list is empty or not

In this article, we will learn How to check if the given list is empty or not. 

Example:

Input: ['Geeks', 'Geeks', 'Geeks', 'Geeks', ]
Output: Yes Not Empty
Input: [ ]
Output: Empty

How to check if a list is empty in Python

Method 1: Check the empty list using the len() With Comparison Operator

Let’s see how we can check whether a list is empty or not, in a less pythonic way. We should avoid this way of explicitly checking for a sequence or list

Python3

# Python code to check for empty list
# Explicit way

def Enquiry(lis1):
    if len(lis1) == 0:
        return 0
    else:
        return 1

# Driver Code
lis1 = []
if Enquiry(lis1):
    print("The list is not empty")
else:
    print("Empty List")

Output:

Empty List

Time complexity: O(n)

Auxiliary space: O(n), where n is length of list

Method 2: Check the empty list using the implicit booleans

Now let’s see a more pythonic way to check for an empty list. This method of a check is an implicit way of checking and more preferable than the previous one.

Python3

# Python code to check for empty list
# IMPLICIT way or Pythonic way
def Enquiry(lis1):
    if not lis1:
        return 1
    else:
        return 0

# Driver Code
lis1 = []
if Enquiry(lis1):
    print("The list is Empty")
else:
    print("The list is not empty")

Output:

The list is Empty

Method 4: Check the empty list using the PEP 8 recommended method

This is another method that allows us to determine whether a list in Python is empty. The most Pythonic method of checking the same is shown below.

Python3

list1 = {"a": 1, "b": 2, "c": 3}
list2 = []

if list2:
    print("list is not empty")
else:
    print("list is empty")

Output:

list is empty

Numpythonic way

Example 1

The previous methods that we used in normal Python don’t work for the Numpythonic way. Other methods that work fine for lists or other standard containers fail for NumPy arrays. This way fails with NumPy arrays because Numpy tries to cast the array to an array of bools and if this tries to evaluate all of those bools at once for some kind of aggregate truth value, it fails so we get a ValueError. 

Python3

# Numpythonic way with the previous method
# Returns ValueError
import numpy

def Enquiry(lis1):
    return(numpy.array(lis1))

# Driver Code
lis1 = [0, 1]
if Enquiry(lis1):
    print("Not Empty")
else:
    print("Empty")

Output:

None

Error:

Traceback (most recent call last):
  File "/home/2d237324bb5211d7216c521441a750e9.py", line 7, in 
    if Enquiry(lis1):
ValueError: The truth value of an array with more than 
one element is ambiguous. Use a.any() or a.all()

Example 2

In this example, we will see that even if the list is Not Empty, the output will show Empty. If the list contains one 0, then the if statement will incorrectly result. 

Python3

# Numpythonic way with the previous method
# Returns wrong result
import numpy


def Enquiry(lis1):
    return(numpy.array(lis1))


# Driver Code
lis1 = [0, ]
if Enquiry(lis1):
    print("Not Empty")
else:
    print("Empty")

Output:

Empty

Making the Numpythonic way work

Example 1

If we have a NumPy array then the correct method in all cases is to use if .size. This size checks the size of the arrays and returns True or False accordingly. Example: 

Python3

# Numpythonic way to check emptiness
# Use of size
import numpy

def Enquiry(lis1):
    return(numpy.array(lis1))


# Driver Code
lis1 = []
if Enquiry(lis1).size:
    print("Not Empty")
else:
    print("Empty")

Output:

Empty

Example 2

This example shows the other case with a single 0 element, which failed in the previous cases. 

Python3

# Numpythonic way to check emptiness
# Use of size
import numpy

def Enquiry(lis1):
    return(numpy.array(lis1))

# Driver Code
lis1 = [0, ]
if Enquiry(lis1).size:
    print("Not Empty")
else:
    print("Empty")

Output:

Not Empty

Method 5 : Comparing given list with empty list using != operator

Python3

# Python code to check for empty list
lis1 = []
if lis1!=[]:
    print("The list is not empty")
else:
    print("Empty List")

Output

Empty List

Method: Using list comprehension + len() 

Python3

lst= ['Geeks', 'Geeks', 'Geeks', 'Geeks', ]
x=["not empty" if len(lst)>0 else "empty"]
print(x)

Output

['not empty']

 Using the any() function:

 The any() function returns True if any element in an iterable is True, and False otherwise. This can be used to check if a list is empty or not by passing the list to any() as an argument.

Here is an example of how to use any() to check if a list is empty:

Python3

def is_empty(lst):
    return not any(lst)

lst1 = [1, 2, 3]
lst2 = []

print(is_empty(lst1))  # Output: False
print(is_empty(lst2))  # Output: True

Output

False
True

Method : Comparing given list with empty list using == operator

Python3

# Python code to check for empty list
lis1 = []
if lis1==[]:
    print("Empty List")
else:
    print("The list is not empty")

Output

Empty List

This approach has the advantage of being concise and easy to understand. It is also generally faster than other approaches that involve looping through the elements of the list.