Python check that list is empty

How to check if a list is empty in Python?

Are you a Python developer, grappling with the challenge of check whether or not a list is empty in Python? Regardless of your level of expertise, be it novice or seasoned, it is not uncommon to encounter such hurdles in the course of programming. In this blog post, we will furnish you with a step-by-step guide on how to determine if a list is empty in Python.

Now, the question that begs an answer is, why is it of utmost importance to know how to check if a list is empty in Python? As a Python developer, you will inevitably come across many scenarios that require you to manipulate lists. Without the proper knowledge on how to check whether a list is empty or not, you run the risk of incurring unforeseen errors and bugs in your code. Being cognizant of how to check if a list is empty will assist you in circumventing these complications and makes the writing of more efficient code.

Without further ado, let us delve into the crux of the matter and learn how to determine if a list is empty in Python. By the end of this article, you shall have acquired a lucid comprehension of how to determine if a list is empty in Python, and you shall be equipped with the confidence to apply this knowledge in your coding endeavors.

How to Check if a List is Empty?

Python treats empty lists as False, therefore if a list were supplied as an input, the bool() method would return False. Placing a list within an if statement, utilizing the len() methods, or comparing it to an empty list are other ways to determine whether a list is empty. We’ll see how to use Python to determine if the provided input list is empty or not.

1. not Operator

In Python, one can utilize the not operator to ascertain whether a list is empty or not. An empty list is regarded as False, whereas a non-empty list is considered True.

Here’s an example:

def is_list_empty(lst): if not lst: return True else: return False my_list = [] print(is_list_empty(my_list)) # Output: True my_list = [1, 2, 3] print(is_list_empty(my_list)) # Output: False 

2. len() Function

The len() function in Python can be used to check if a list is empty or not. A list is considered empty if it has no elements. In Python, the length of an empty list is 0.

Here’s an example:

def is_list_empty(lst): if len(lst) == 0: return True else: return False # Example usage >>> my_list = [] >>> is_list_empty(my_list) True >>> my_list = [1, 2, 3] >>> is_list_empty(my_list) False 

In this example, the is_list_empty() function takes a list as an argument and returns True if the length of the list is 0, and False otherwise

3. By Comparing with an Empty List

You can also check if a list is empty by comparing it with an empty list in Python. Here’s an example:

my_list = [] if my_list == []: print("The list is empty.") else: print("The list is not empty.") 

This method works because [] is the empty list in Python, and comparing two lists with the == operator returns True if the lists contain the same elements in the same order, and False otherwise. So, comparing a list with [] will return True if the list is empty and False otherwise.

4. __len__() Method

Yes, you can use the __len__() method to check if a list is empty or not. The __len__() method is a special method in Python that returns the number of elements in an object, such as a list. Here’s an example:

my_list = [] if len(my_list) == 0: print("The list is empty.") else: print("The list is not empty.") 

In this example, the len function is called on the my_list object, which returns the number of elements in the list. If the number of elements is 0, it means the list is empty, and the if statement outputs «The list is empty.»

5. NumPy Module

You can use the numpy.size function to check if a NumPy array is empty or not.

import numpy as np a = np.array([]) if np.size(a) == 0: print("Array is empty") else: print("Array is not empty") 

Alternatively, you can use the numpy.shape function and check if the first element of the shape tuple is equal to zero.

import numpy as np a = np.array([]) if np.shape(a)[0] == 0: print("Array is empty") else: print("Array is not empty") 

Conclusion

So there you have it, a brief overview of how to check whether a list is empty in Python. With these methods in your toolkit, you’ll be well on your way to building effective and efficient programs that can handle lists of all shapes and sizes.

We learned how to use the not operator in this article to check if a statement is true or false. We learned how to use the len() method to get a list’s length. This may be used to get the length of a tuple, dictionary, string, etc. In addition, we learned how to calculate a NumPy array’s size and length as well as how to generate a NumPy array from a list.

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Python isEmpty() equivalent – How to Check if a List is Empty in Python

Ihechikara Vincent Abba

A list is one of the data structures in Python that you can use to store a collection of variables.

In some cases, you have to iterate through and perform an operation on the elements of a list. But you can’t loop/iterate through a list if it has no elements in it.

In this article, you’ll learn how to check if a list is empty by:

• Using the not operator.
• Using the len() function.
• Comparing the list to an empty list.

How To Check if a List Is Empty in Python Using the not Operator

The not operator in Python is used for logical negation. Here’s an example:

x = True y = False print(not x) # Output: False print(not y) # Output: True 

not returns true when an operand is false, and false if an operand is true.

You can check if a collection is empty using the logic above. Here’s how:

people_list = [] if not people_list: print("Your list is empty") else: print("Your list is not empty") # Your list is empty

In the code above, we used an if statement and the not operator to check if the people_list was empty.

How To Check if a List Is Empty in Python Using the len() Function

You can use the len() function in Python to return the number of elements in a data structure.

people_list = ["John", "Jane", "Jade", "Doe"] print(len(people_list)) # 4

Using the len() function, we printed the length of the people_list list which had four elements.

You can also get the length of an empty list:

people_list = [] print(len(people_list)) # 0

Now that we know that the length of an empty list is 0, we use it to check if a list is empty:

people_list = [] if len(people_list) == 0: print("Your list is empty") else: print("Your list is not empty") # Your list is empty

How To Check if a List Is Empty in Python By Comparing To an Empty List

An interesting way to check if a list is empty is by comparing it to another empty list. That is:

people_list = [] if people_list == []: print("Your list is empty") else: print("Your list is not empty") # Your list is empty

In the example above, we compared the people_list list to an empty list: if people_list == []

You can play around with the code by adding elements to the list to see which if. else statement gets executed.

Summary

In this article, we saw how to check if a list is empty in Python by using three different methods.

We saw how to check if a list is empty by using the not operator, and the len() function.

We also saw how check if a list is empty by comparing it to an empty list.

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How to Check if a List is Empty in Python?

Python provides several ways to check if a list is empty or not. This tutorial will guide you through the different methods to check if a list in empty in Python. The methods we’ll explore include:

1. The len() function
2. The “not” operator
3. Comparing the list to an empty list
4. The all() function
5. The any() function

Check if a List is Empty in Python

Here are the 5 different ways to check if a list is empty in Python with examples.

1. Using the len() Function

The len() function is a built-in Python function that returns the number of items in an object. When it’s applied to a list, it returns the number of elements in the list. If a list is empty, the len() function will return 0.

Here’s how you use the len() function to check if a list is empty:

my_list = [] if len(my_list) == 0: print("The list is empty.") else: print("The list is not empty.")

You can see the output here:

Here’s an example of checking a non-empty list using the len() function:

my_list = [1, 2, 3] if len(my_list) == 0: print("The list is empty.") else: print("The list is not empty.")

2. Using the “not” Operator

The “not” operator in Python returns True if the operand (the value it’s operating on) is False. In the context of lists, an empty list is considered False when converted to a Boolean context, while a non-empty list is considered True.

Here’s how you can use the “not” operator to check if a list is empty:

my_list = [] if not my_list: print("The list is empty.") else: print("The list is not empty.")

Here’s how you use the “not” operator to check a non-empty list:

my_list = [1, 2, 3] if not my_list: print("The list is empty.") else: print("The list is not empty.")

Here the output will come as:

3. Comparing the List to an Empty List

You can also check if a list is empty by comparing it directly to an empty list ([]). This method might be less readable than the others if you’re new to Python, but it’s still effective.

my_list = [] if my_list == []: print("The list is empty.") else: print("The list is not empty.")

Here’s how you check a non-empty list by comparing it to an empty list:

my_list = [1, 2, 3] if my_list == []: print("The list is empty.") else: print("The list is not empty.")

4. Using the all() Function

The all() function returns True if all elements in the list are True. An empty list doesn’t have any elements, so all() returns True for an empty list.

However, be careful when using this method. If your list includes any elements that Python considers False (like 0, False, or an empty string), all() will return False, even if the list is not empty.

my_list = [] if all(my_list): print("The list is empty.") else: print("The list is not empty.")

Here’s an example of checking a non-empty list using the all() function:

my_list = [1, 2, 3] if all(my_list): print("The list is empty.") else: print("The list is not empty.")

Note: The all() function returns True if all elements in the iterable are True . So if the list contains any ‘falsy’ values (like 0, False, None or an empty string), all() will return False .

5. Using the any() Function

The any() function returns True if at least one element in the list is True. An empty list doesn’t have any elements, so any() returns False for an empty list.

Like with all(), be aware that this method considers the truthiness of the list’s elements. If your list includes elements that Python considers False, any() might not work as you expect.

Here’s how you use the any() function:

my_list = [] if not any(my_list): print("The list is empty.") else: print("The list is not empty.")

Here’s an example of checking a non-empty list using the any() function:

my_list = [1, 2, 3] if not any(my_list): print("The list is empty.") else: print("The list is not empty.")

Note: The any() function returns True if at least one element in the iterable is True . So even if there are ‘falsy’ values in the list, as long as there’s at least one ‘truthy’ value, any() will return True .

Conclusion

These are some of the most common ways to check if a list is empty in Python. They all have their use cases, so choose the one that best suits your needs. Understanding how to properly check for empty lists is essential for effective data handling and control flow in Python.

I am Bijay Kumar, a Microsoft MVP in SharePoint. Apart from SharePoint, I started working on Python, Machine learning, and artificial intelligence for the last 5 years. During this time I got expertise in various Python libraries also like Tkinter, Pandas, NumPy, Turtle, Django, Matplotlib, Tensorflow, Scipy, Scikit-Learn, etc… for various clients in the United States, Canada, the United Kingdom, Australia, New Zealand, etc. Check out my profile.

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