As mentioned, when the number of arguments doesn't match the definition, Python triggers a TypeError and the program crashes (stops executing).
Here is a breakdown of what happens internally and what you will see:
1. The Execution Stops
Python will not try to "guess" what you meant. Unlike some other languages that might set missing arguments to null or undefined, Python prefers to stop immediately so that you don't perform calculations with missing data.
2. You get a Traceback
Python provides a clear error message in the terminal. Let's look at the two specific types of mismatches:
Case A: Not enough arguments
If you have def add(a, b): but call add(5):
- Error:
TypeError: add() missing 1 required positional argument: 'b' - Meaning: "I needed two pieces of info, but you only gave me one. I can't finish the job without 'b'."
Case B: Too many arguments
If you have def greet(name): but call greet("Carlos", "Admin"):
- Error:
TypeError: greet() takes 1 positional argument but 2 were given - Meaning: "You gave me extra information that I have no place to store."
How to test it in your current environment:
Open your arguments.py file and try calling say_hello() without any name:
def say_hello(name):
print(f'Hello {name}')
# This will cause an error because 'name' is missing
say_hello() Run it with python3 arguments.py, and you will see the TypeError in your terminal.
Pro-tip: Later in this lab, you will learn about Keyword Arguments and Default Values, which are techniques used to make functions more "forgiving" when it comes to argument counts!
