String concatenation is the process of joining two or more strings together to form a single string.

Python uses the + operator to concatenate strings.

When two strings are joined using the + operator, Python creates a new string containing the combined contents of both strings. The original strings remain unchanged because strings are immutable.

String concatenation is commonly used to build messages, combine names, create file paths, and generate formatted output.

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Syntax #

string1 + string2

Components #

Component	Description
string1	First string.
+	Concatenation operator.
string2	Second string.

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Example 1: Concatenating Two Strings #

main.py

first = "Hello"
second = "World"

result = first + second

print(result)

Output #

HelloWorld

Explanation #

• The + operator joins the two strings.
• No space is added automatically.
• A new string "HelloWorld" is created.

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Example 2: Concatenating with a Space #

main.py

first = "Hello"
second = "World"

result = first + " " + second

print(result)

Output #

Hello World

Explanation #

• A space is itself a string (" ").
• It is concatenated between the two words.
• The final result becomes "Hello World".

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Example 3: Joining Multiple Strings #

main.py

language = "Python"
version = "3.14"
edition = "Tutorial"

text = language + " " + version + " " + edition

print(text)

Output #

Python 3.14 Tutorial

Explanation #

• Multiple strings can be concatenated in a single expression.
• Each + operator joins another string.
• The result is one complete string.

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Example 4: Concatenating User Input #

main.py

first_name = input("Enter first name: ")
last_name = input("Enter last name: ")

full_name = first_name + " " + last_name

print(full_name)

Sample Input #

John
Doe

Output #

John Doe

Explanation #

• input() returns strings.
• Both input strings are joined with a space.
• The result is stored in full_name.

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Example 5: Concatenating Numeric Strings #

main.py

num1 = "10"
num2 = "20"

print(num1 + num2)

Output #

1020

Explanation #

• Both values are strings.
• Concatenation joins the characters.
• Python does not perform arithmetic addition.

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Example 6: Concatenating Empty Strings #

main.py

text = ""
word = "Python"

print(text + word)

Output #

Python

Explanation #

• An empty string contributes no characters.
• The result is simply "Python".

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Example 7: Using += for Concatenation #

main.py

message = "Hello"

message += " World"

print(message)

Output #

Hello World

Explanation #

• += appends another string.
• A new string is created and assigned back to message.
• The original string object is replaced.

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Example 8: Building a Sentence #

main.py

subject = "Python"
verb = "is"
adjective = "powerful"

sentence = subject + " " + verb + " " + adjective + "."

print(sentence)

Output #

Python is powerful.

Explanation #

• Individual words are joined together.
• Spaces and punctuation are also strings.
• The resulting string forms a complete sentence.

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Example 9: Concatenating Special Characters #

main.py

username = "admin"
domain = "@example.com"

email = username + domain

print(email)

Output #

admin@example.com

Explanation #

• Special characters such as @ can be part of strings.
• Concatenation joins both parts to create an email address.

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Example 10: Verifying the Result Type #

main.py

first = "Py"
second = "thon"

result = first + second

print(result)
print(type(result))

Output #

Python
<class 'str'>

Explanation #

• Concatenation always produces another string.
• The data type of the result is str.

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Common Mistakes #

1. Trying to Concatenate a String and an Integer #

Incorrect

age = 25

print("Age: " + age)

Output #

TypeError: can only concatenate str (not "int") to str

Reason

The + operator can concatenate only strings.

Correct

age = 25

print("Age: " + str(age))

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2. Expecting Spaces to Be Added Automatically #

Incorrect

first = "Hello"
second = "World"

print(first + second)

Incorrect Expectation #

Hello World

Actual Output #

HelloWorld

Reason

Python does not automatically insert spaces.

Correct

print(first + " " + second)

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3. Confusing Concatenation with Addition #

Incorrect

print("15" + "25")

Incorrect Expectation #

40

Actual Output #

1525

Reason

Both operands are strings, so Python joins them instead of adding their numeric values.

Correct

print(int("15") + int("25"))

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4. Assuming Concatenation Modifies the Original String #

Incorrect

text = "Hello"

text + " World"

print(text)

Output #

Hello

Reason

Concatenation returns a new string.
The original string remains unchanged unless the result is assigned.

Correct

text = text + " World"

print(text)

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Best Practices #

• Insert spaces explicitly when joining words.
• Convert non-string values using str() before concatenation.
• Use meaningful variable names for readability.
• Assign the concatenated result to a variable if it will be reused.
• For complex formatted strings, consider using f-strings (covered later).

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Key Points to Remember #

• String concatenation joins two or more strings.
• The + operator is used for concatenation.
• The += operator appends one string to another.
• Python does not automatically insert spaces.
• Concatenation creates a new string because strings are immutable.
• Both operands must be strings.
• The result of concatenation is always of type str.