The Python len() function is one of the most frequently used functions. It returns the length, or the number of elements, of collections (lists, tuples, dictionaries, etc.) or strings, making it a simple yet highly useful tool. In this post, we will delve into the details of the len() function in Python and explore various ways to use it.
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What is the len() Function?
The len() function in Python returns the length of a data structure, such as a list, string, tuple, or dictionary. It tells you how many elements are present in each of these structures. This function is highly intuitive and helps make Python code concise, making it a favorite among both beginner and experienced developers.
Basic Usage: Using len() to Get the Length of Lists, Tuples, and Sets
The basic usage of the len() function is very simple. Just pass in the data, and it will return the length. The following code demonstrates how to get the length of my_list, my_tuple and my_set using lists, tuples and set, respectively.
my_list = [1, 2, 3, 4, 5, 6, 7, 8]
len(my_list)
my_tuple = (1, 3, 5, 7)
len(my_tuple)
my_set = {2, 4, 6, 8, 10}
len(my_set)In this code, the list my_list contains 8 elements, so len(my_list) returns 8. Similarly, my_tuple has 4 elements, and my_set has 5 elements, so the function returns 4 and 5, respectively.
Using len() to Get the Length of a String
The len() function is also useful when determining the length of a string. The length of a string is counted character by character, including spaces.
my_string = "Hello, World!"
len(my_string)In this case, the string “Hello, World!” consists of 13 characters, so the len() function returns 13. One key point to note here is that spaces are also counted as characters.
Using len() to Get the Number of Dictionary Entries
The len() function can also be used to find the number of entries in a dictionary. In the case of a dictionary, each key-value pair is treated as a single entry.
my_dict = {'a': 1, 'b': 2, 'c': 3}
len(my_dict)Since the dictionary my_dict contains 3 key-value pairs, len(my_dict) returns 3.
Important Cautions When Using len()
Getting the Length of Lists Within a List
If there is a list containing other lists as elements, the len() function will only return the length of the outer list, considering each inner list as a single element.
nested_list = [[1, 2, 3], [4, 5], [6], [7, 8, 9]]
len(nested_list)In this example, the nested_list contains 4 inner lists, so len(nested_list) returns 4.
Getting the Length of Numbers
The len() function works on various data types in Python, but it cannot be used on integers or floats. If you try to get the length of an integer or a float, an error will occur.
Pythonnum_int = 12345
num_float = 12.345
len(num_int)
len(num_float)Running the code above results in an error message such as “TypeError: object of type ‘int’ has no len()”, indicating that the len() function cannot be used on numbers.
Therefore, if you want to determine the length of a number, you need to convert it to a string first.
Pythonnum_int = 12345
num_float = 12.345
len(str(num_int))
len(str(num_float))Running the code above will return the length of the integer as 5 and the length of the float as 6.
Summary
Python len() function is an incredibly useful tool when handling data in Python. It can be used to get the length of various data structures, such as lists, tuples, sets, strings, and dictionaries, making code concise and intuitive. It also offers flexibility by allowing the definition of an object’s length when applied to custom classes.
Because the Python len() function is simple yet frequently used, it is widely employed by both beginners and experienced programmers alike. Using len() actively will improve the readability of your Python code and make data processing more convenient.