TypeError: takes 1 positional argument but 2 were given

What you see

class Greeter:
    def hello(name):
        return f"Hello, {name}"

print(Greeter().hello("Ada"))

Traceback (most recent call last):
  File "/home/me/project/main.py", line 5, in <module>
    print(Greeter().hello("Ada"))
          ~~~~~~~~~~~~~~~^^^^^^^
TypeError: Greeter.hello() takes 1 positional argument but 2 were given

What it means

When you call a method on an object, Python passes the object itself as the first argument. Greeter().hello("Ada") is really Greeter.hello(the_greeter, "Ada"): two arguments. hello was written with one parameter, so the object takes name and "Ada" has nowhere to go.

That is why the count is one more than you typed. The extra one is the object, which is conventionally called self.

Why it happens

• A method without self, as in the example.
• A string where a tuple was meant. Thread(target=work, args=("ada")) passes three arguments, one per letter, because ("ada") is just a string in brackets. A one-item tuple needs a comma: ("ada",).
• A callback that receives more than you expect. Tkinter's bind() passes an event object to the handler; command= does not.
• Plainly too many arguments for a function.

How to fix it

Add self as the first parameter of the method:

class Greeter:
    def hello(self, name):
        return f"Hello, {name}"

If the method does not need the object, mark it @staticmethod, and Python stops passing it:

class Greeter:
    @staticmethod
    def hello(name):
        return f"Hello, {name}"

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.

3.9 names the method as "hello()". From 3.10 the message names its class too, "Greeter.hello()", which makes the method easier to find.