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

What you see

age = 36
print("Age: " + age)

Traceback (most recent call last):
  File "/home/me/project/main.py", line 2, in <module>
    print("Age: " + age)
          ~~~~~~~~^~~~~
TypeError: can only concatenate str (not "int") to str

What it means

+ between two strings joins them. Between a string and a number it is an error: Python does not turn 36 into "36" on its own, because it cannot know whether you wanted text or arithmetic.

The type in brackets is the one on the right of the +. With a list it says (not "list"), with None it says (not "NoneType").

Why it happens

• Building a message with + from text and numbers, as in the example.
• A number from a calculation joined to a label: "Total: " + price * qty.
• A value you expected to be text that is a number, from JSON or a database.

How to fix it

An f-string is the usual way. It converts each value for you:

print(f"Age: {age}")

Or convert explicitly with str():

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

print() with commas also works, and puts a space between items: print("Age:", age).

How each Python version words it

Run on CPython 3.9.6, 3.10.22, 3.11.17, 3.12.15, 3.13.17, 3.14.9 and 3.15.1, on October 25, 2026.

The wording is the same in every version here. With the number on the left, 36 + " years", the message is different: "unsupported operand type(s) for +: 'int' and 'str'".