To get the length of the list in python you can use the len() function. Len() Function is an inbuilt function in python and returns a number of elements present in the list object.
Syntax
len(list)
Return Value
This method returns the number of items in the list.
Example of get size of list Python
# Python program to demonstrate working
list1 = [10, 20, 30]
n = len(list1)
print("The length of list is: ", n)
Output: 3
len() method error if Use it with Python String
You will get an error If you using it like that to get the length of the string in python.
a = "Hello, World!" print(a.len())
Output:
AttributeError: ‘str’ object has no attribute ‘len’
Right way to do it:-
a = "Hello, World!" print(len(a))
Output: 13
EMPTY list length
If list is empty then len() function will return 0.
list1 = [] print(len(list1))
Output: 0
Interview Questions
Here are some common interviews questions on get size of list Python.
Q: What is “len function” time complexity?
Answer: len() works in O(1) time as list is an object.
Q: How do I get the number of elements in a list?
Answer: Use python length method “len()” to get the size of list. See below example of it.
# empty list
items = []
items.append("apple")
items.append("orange")
items.append("banana")
# Get and print number of elements in the list
print(len(items))
Output: 3
Q: What is the best way to find the length of a list in Python?
Answer: The best way to find the length of List in python use Len() function.
Q: How to get the Python length of the Array?
Answer: Python doesn’t have an array data type. Python is using a “List” data type instead of an Array. Both works the same but there are some differences.
Where Array is using in Java, C++ and other programming language and Lists are used in Python.
#Python length of list in dictionary
The following example shows the usage of “len() method” to get Python dict length.
dict1 = {'Name': 'John', 'Age': 72};
print("Length: ", len(dict1))
Output: Length: 2
Do comment if you have any questions and suggestions on this tutorial.
Note: This example (Project) is developed in PyCharm 2020.1 (Community Edition)
JRE: 1.8.0
JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
macOS 10.15.4
Python 3.7
All Python Programs code are in Python 3, so it may change its different from python 2 or upgraded versions.