A python list is a collection of elements.

Length of a list in python is the total number of elements in it.
Length is also referred as the size of list.

This article will explain 3 ways in which python list length can be checked.

Method 1: Using len() function

Python’s inbuilt len() function accepts an object as arguments and returns the number of items in it or the length or size of the object.

Python docs for len() state

Return the number of items in a container.

Example program that uses len() to get the size of list follows.

list_numbers = [1,3,5,6,7,9]
length = len(list_numbers)
print("Length of list is :", length)

which prints

Method 2: Using for loop

This is a traditional method of calculating the length of a list and should be used when you are asked to get the list length without using len() function or any other built in python method.

This method iterates over the list and in every iteration increments a variable by 1. This variable is initialized to 0 before the start of iteration.
At the end of loop, the value of this element will be equal to the number of iterations or the number of elements in the list.
Example,

list_numbers = [1,3,5,6,7,9]
# initialize variable to 0
length = 0
# iterate list
for i in list_numbers:
   # increment variable
   length += 1
print("Length of list is :", length)

A python list can be iterated in many ways but here we are using a for loop.
Output of this example is

This is not a recommended method since it requires iterating the complete list. For larger list, it may be quite slow.

Method 3: Using operator module

Python’s operator module contains a function length_hint() which accepts an object argument and returns the count of its elements.
Example,

from operator import length_hint

list_numbers = [1,3,5,6,7,9]
length = length_hint(list_numbers)
print("Length of list is :", length)

Before using length_hint function, you need to import the module and function itself as shown above. The example prints

Out of all the three methods to get the length of list, len() function is the fastest and you should use this only, if not asked otherwise.

Conclusion

In conclusion, this article has provided various methods to obtain the length of a list in Python, catering to different programming preferences and scenarios.
Method 1 demonstrated the simplicity and efficiency of using the built-in len() function, offering a straightforward solution for obtaining the length of a list.

Method 2 showcased the versatility of using a for loop to iterate through the list elements, allowing for additional computations or conditions if needed.

Lastly, Method 3 introduced the utilization of length_hint() function from operator module, highlighting its capability to perform advanced operations efficiently.
Whether you prefer a concise approach, a loop-based solution, or leveraging external modules, mastering these techniques will undoubtedly enhance your Python programming skills and efficiency in list manipulation tasks.