Typeerror can only Concatenate str not int to str in Python

typeerror can only concatenate str not int to str

Programmers love Python’s versatility, readability, and user-friendliness. As with any language, it has its own set of challenges. One challenge frequently trips up programmers is the notorious “typeerror can only concatenate str not int to str”. This error, often befuddled for both novices and experienced developers, is a roadblock to efficient coding. In this comprehensive blog, we embark on a journey to demystify this error, delve into Python’s intricate data types, master the art of variable type checking, explore the functionalities of the str() function, and equip ourselves with strategies to sidestep this common pitfall gracefully.

What is TypeError?

Before plunging into the intricacies of the “TypeError: can only concatenate str (not ‘int’) to str”, let’s first understand what a TypeError entails. In Python, a TypeError occurs when an operation is executed on objects with incompatible data types. This error surfaces when you attempt to use an operator or a function in a manner that is unsupported by the given data types.

Why does this error occur?

The specific error message “can only concatenate str (not ‘int’) to str” rears its head when you endeavour to concatenate (join) a string and an integer using the + operator. In Python, the + the operator wears multiple hats: it concatenates strings and performs mathematical addition on numerical values. However, concatenating a string and an integer directly using this operator is an error-prone operation due to Python’s robust type system.

This example illustrates the point.

name = "John"
age = 25
result = name + age  
# This will trigger the TypeError

In this scenario, you might expect the name and age variables to merge seamlessly, but you encounter a TypeError.

Different Data Types in Python

Python’s strength lies in its support for diverse data types, each catering to unique use cases. Here’s a snapshot of some foundational data types in Python:

  1. int: The backbone of integers, encompassing values such as 1, -5, and 1000.
  2. float: The realm of floating-point numbers, complete with decimal precision. Think of numbers like 3.14 and -0.5.
  3. str: Strings, the building blocks of textual information, enclosed within single or double quotes.
  4. list: Ordered collections of items, ready to be manipulated.
  5. tuple: Similar to lists, but immutable – their content cannot be altered after creation.
  6. dict: The powerhouses of key-value pairs, facilitating efficient data mapping.
  7. bool: The guardians of truth – representing Boolean values, True or False.

How to Check the Data Type of a Variable

To navigate the treacherous waters of the “TypeError: can only concatenate str (not ‘int’) to str”, a solid understanding of variable data types is imperative. Enter the trusty type() function – a built-in gem that unveils the data type of a variable:

age = 25


The str() Function

To liberate yourself from the clutches of the TypeError quandary while merging a string and an integer, you need the magical str() function. This function, akin to an alchemist’s potion, transmutes an integer into a string, harmonizing the elements of your concatenation puzzle:

name = "John"
age = 25
result = name + str(age)  

By invoking str(age), you execute a metamorphosis, converting the numeric age into a string before seamlessly fusing it with the name string.

Other Ways to Concatenate Strings and Integers

The str() function isn’t the sole troubleshooter for the conundrum of amalgamating strings and integers. Python offers diverse avenues to achieve concatenation nirvana sans the ominous TypeError. One such avenue is the realm of formatted strings, more commonly known as f-strings:

result = f"My name is {name} and I am {age} years old."

In this realm, the prefix ‘f’ is your gateway to a utopia of f-strings, enabling you to embed variables within your prose seamlessly. The variables, encased within curly braces, elegantly assimilate within the text.

Avoiding TypeErrors in Python

While the “TypeError: can only concatenate str (not ‘int’) to str” is a prominent antagonist, it’s just a solitary example amidst a trove of type-related conundrums that Python developers may encounter. To cultivate error-free and robust code, consider these time-honoured principles:

  1. Check Data Types: Nurturing awareness of data types is pivotal. Utilize the type() function as your compass to decipher the nature of variables.
  2. Embrace Type Conversion: When the occasion demands operations across diverse data types, seek solace in appropriate type conversion functions – str(), int(), float(), and their kin.
  3. Champion Formatted Strings: Unleash the potential of formatted strings (f-strings), where variables seamlessly integrate into text without the burden of explicit conversion.
  4. Cultivate Conditional Vigilance: In scenarios involving dynamic data or user inputs, erect the fortress of conditional checks. These guardians gracefully navigate potential type mismatches.
Data TypeDescriptionExample ConcatenationResult
intRepresents integersage = 25<br>result = “Age: ” + ageTypeError
floatRepresents floating-point numbersprice = 9.99<br>result = “Price: $” + priceTypeError
strRepresents stringsname = “John”<br>greeting = “Hello, ” + nameHello, John
listRepresents ordered collections of itemsfruits = [“apple”, “banana”]<br>list_str = “Fruits: ” + fruitsTypeError
tupleSimilar to lists, but immutablecoordinates = (3, 5)<br>coord_str = “Coordinates: ” + coordinatesTypeError
dictRepresents key-value pairs in a dictionaryinfo = {“name”: “Alice”, “age”: 30}<br>info_str = “Info: ” + infoTypeError
boolRepresents Boolean values (True or False)status = True<br>status_str = “Status: ” + statusTypeError

In this table, you can observe how attempting to concatenate a string with an int, float, list, tuple, or dict leads to a TypeError. The focus is on showcasing scenarios that trigger the error for illustrative purposes. On the other hand, concatenating a string with another string (str).


The “typeerror can only concatenate str not int to str” looms as a timeless enigma, greeting newcomers and veterans in the Python domain. Understanding the roots of Python, type conversions, and the myriad paths to amalgamation empower you to script Python code that transcends pitfalls and manifests as a testament to craftsmanship. Use Python’s strong typing as your ally to detect errors early, safeguarding reliability and enabling efficiency. You will experience an exhilarating journey toward Python mastery. Armed with their wisdom, you will solve even the most bewildering type-related challenges.

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