The length of a string is the total number of characters it contains.

Python provides the built-in len() function to determine the length of a string.

The len() function counts every character, including letters, digits, spaces, punctuation marks, and special characters.

Knowing the length of a string is useful when validating user input, processing text, checking password lengths, and controlling loops.

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Syntax #

len(string_name)

Components #

Component	Description
len()	Built-in function that returns the number of characters.
string_name	The string whose length is to be calculated.

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Example 1: Finding the Length of a String #

main.py

language = "Python"

print(len(language))

Output #

6

Explanation #

• "Python" contains six characters.
• The len() function counts all characters.
• The returned value is 6.

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Example 2: Length of a Sentence #

main.py

sentence = "Python is easy."

print(len(sentence))

Output #

15

Explanation #

• The string contains letters, spaces, and a period.
• Spaces and punctuation are also counted as characters.
• Therefore, the total length is 15.

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Example 3: Length of an Empty String #

main.py

text = ""

print(len(text))

Output #

0

Explanation #

• An empty string contains no characters.
• Therefore, its length is 0.

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Example 4: Length of a Numeric String #

main.py

number = "123456789"

print(len(number))

Output #

9

Explanation #

• Although the string contains digits, each digit is treated as a character.
• There are nine characters in the string.

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Example 5: Length with Special Characters #

main.py

password = "@Python#2026"

print(len(password))

Output #

12

Explanation #

• Letters, digits, and special symbols are all counted.
• Every character contributes to the total length.
• The length of the string is 12.

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Example 6: User Input #

main.py

name = input("Enter your name: ")

print(len(name))

Sample Input #

Alexander

Output #

9

Explanation #

• The user enters a string.
• len() counts the number of characters entered.
• "Alexander" contains nine characters.

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Example 7: Length of a String with Spaces #

main.py

message = "Good Morning"

print(len(message))

Output #

12

Explanation #

• The space between the two words is counted.
• "Good" contains four letters.
• "Morning" contains seven letters.
• Including the space, the total length becomes 12.

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Example 8: Storing the Length #

main.py

text = "Programming"

length = len(text)

print(length)

Output #

11

Explanation #

• len(text) returns the length of the string.
• The result is stored in the variable length.
• Printing length displays 11.

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Example 9: Using len() in an Expression #

main.py

word = "Python"

print(len(word) + 4)

Output #

10

Explanation #

• len(word) returns 6.
• The integer 4 is added to it.
• The final result is 10.

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Example 10: Checking the Type of the Result #

main.py

text = "Python"

length = len(text)

print(length)
print(type(length))

Output #

6
<class 'int'>

Explanation #

• The len() function returns an integer.
• Therefore, its data type is int.

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Common Mistakes #

1. Assuming Spaces Are Not Counted #

Incorrect

text = "Hello World"

print(len(text))

Incorrect Expectation #

10

Actual Output #

11

Reason

The space between "Hello" and "World" is also counted.

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2. Using length() Instead of len() #

Incorrect

text = "Python"

print(length(text))

Output #

NameError: name 'length' is not defined

Reason

Python provides the len() function, not length().

Correct

print(len(text))

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3. Assuming len() Returns a String #

Incorrect

text = "Python"

print(len(text) + "2")

Output #

TypeError: unsupported operand type(s) for +: 'int' and 'str'

Reason

len() returns an integer, not a string.

Correct

print(str(len(text)) + "2")

or

print(len(text) + 2)

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4. Calling len() Without an Argument #

Incorrect

print(len())

Output #

TypeError: len() takes exactly one argument (0 given)

Reason

The len() function requires one argument.

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Best Practices #

• Use len() whenever you need the number of characters in a string.
• Remember that spaces and punctuation are included in the count.
• Store the result in a variable if it will be used multiple times.
• Use meaningful variable names such as length, size, or count.
• Remember that len() returns an integer.

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Key Points to Remember #

• len() returns the number of characters in a string.
• Every character is counted, including spaces and special symbols.
• The length of an empty string is 0.
• len() returns a value of type int.
• len() requires exactly one argument.
• len() does not modify the original string.
• It is one of the most commonly used built-in functions in Python.