Cookbooks
Python
Chapter 2. Strings
Finding the length of a string

Python:
Finding the length of a string

How to: 

# Simple usage of len() function
my_string = "Hello, World!"
length = len(my_string)
print(length)  # Output: 13

# Length in a loop
for i in range(len(my_string)):
    print(my_string[i], end='')  # Outputs: Hello, World!
print()  # For newline

# Combine string length with other operations
if len(my_string) > 10:
    print("It's a long string!")  # Output: It's a long string!

Deep Dive

Historically, the len() function has been Python’s go-to way to find a string’s length. It’s elegant and quick. Underneath, Python strings are arrays of bytes representing Unicode characters, and len() counts those. The function works not just with strings but with any iterable.

Alternatives? Well, not commonly used for strings, but you could loop through a string and count characters manually—unwieldy and inefficient. Before Unicode support, the length of a string was sometimes different from its memory size, but since Python 3’s strings are Unicode-native, the len() accurately represents the number of characters.

Implementation-wise, Python strings are objects with metadata, including length, so len() is actually an O(1) operation—constant time, regardless of string size. That’s like snapping your fingers and getting an answer.

See Also

Extracting substringsInterpolating a string