Python len(): A Practical Guide to Measuring Object Lengths

In Python, len() is a built‑in function that returns the number of items in an object. Whether you’re working with strings, lists, tuples, dictionaries, or other collections, len() gives you a quick, efficient way to determine size without performing any costly iteration.

Syntax

len(value)

Parameter

value – The object whose length you want to measure.

Return Value

Returns an integer representing the number of elements in the supplied object.

Strings

For a string, len() counts every character—including spaces, punctuation, and special symbols. Be cautious when passing a None value, as it will raise a TypeError.

Collections

• Lists & Tuples – Counts the number of elements.
• Dictionaries – Counts key‑value pairs; keys and values are not separated.
• Sets & Frozensets – Counts unique items.

Edge Cases

• Empty objects – len([]) returns 0.
• Unsupported types – Passing a non‑sized type (e.g., int) raises TypeError.

Examples

1. String Length

# Example 1
str1 = "Welcome to Guru99 Python Tutorials"
print("The length of the string is:", len(str1))

Output:
The length of the string is: 35

2. List Length

# Example 2
list1 = ["Tim", "Charlie", "Tiffany", "Robert"]
print("The length of the list is", len(list1))

Output:
The length of the list is 4

3. Tuple Length

# Example 3
tup = ("Jan", "Feb", "March")
print("The length of the tuple is", len(tup))

Output:
The length of the tuple is 3

4. Dictionary Length

# Example 4
dict_obj = {"Tim": 18, "Charlie": 12, "Tiffany": 22, "Robert": 25}
print("The length of the dictionary is", len(dict_obj))

Output:
The length of the dictionary is 4

5. Array Length (List Equivalent)

# Example 5
arr = ["Tim", "Charlie", "Tiffany", "Robert"]
print("The length of the array is", len(arr))

Output:
The length of the array is 4

Key Takeaways

• len() is versatile and efficient for any sized object.
• It returns an integer; zero indicates an empty object.
• Always validate the object type to avoid TypeError.