Fix TypeError in Python

Error Reference

TypeError

TypeErrors arise when an operation receives a value of the wrong type. Here's how to interpret the message and fix it.

Read the messageValidate inputs

Read the message

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

• Check both operands: one is a string, the other an int.
• Convert types or adjust logic (e.g., use f-strings instead of +).

Validation

• Use isinstance checks for defensive programming.
• Provide helpful errors: raise TypeError("expected str, got {type(value).__name__}").
• Add type hints so linters catch mistakes earlier.

Next up in your learning path

ValueError

Differentiate between type vs value problems.

Related

Type casting

Convert inputs before using them.

Companion

Type hints

Document expected types for linters and IDEs.

Reference