The error “TypeError: your_function() got an unexpected keyword argument ‘argument_name’” in Python means you’re calling a function with a keyword argument that the function doesn’t accept. Let’s break down why this happens and how to fix it.
Understanding the Error
Keyword Arguments: In Python, you can pass arguments to a function using Positional arguments (based on the order they’re defined) or Keyword arguments (explicitly naming the argument). For example:
· def greet(name, greeting="Hello"): # name is a positional argument, greeting has a default value and can be a keyword argument
· print(f"{greeting}, {name}!")
·
· greet("Alice") # Positional argument: name="Alice", greeting uses default "Hello"
· greet(name="Bob") # Keyword argument: name="Bob", greeting uses default "Hello"
· greet("Charlie", "Hi") # Positional: name="Charlie", greeting="Hi"
· greet(greeting="Hey", name="David") # Keyword: name="David", greeting="Hey"
The Error: The “unexpected keyword argument” error tells you that the function definition Doesn’t have a parameter with the exact name you’re using in the function call.
Common Causes and Solutions
Here’s a breakdown of the most frequent reasons for this error and how to solve them:
Typo in the Argument Name:
Problem: You’ve simply made a typo in the name of the keyword argument when calling the function. Solution: Carefully check the function definition and make sure the argument name in your function call Exactly matches the parameter name in the function’s definition.
2. def calculate_area(width, height):
3. return width * height
4.
5. # Incorrect:
6. area = calculate_area(widt=5, height=10) # "widt" is a typo!
7.
8. # Correct:
9. area = calculate_area(width=5, height=10)
Incorrect Argument Name:
Problem: You’re using an argument name that’s similar but not the correct one defined in the function. Solution: Double-check the function’s documentation or source code to confirm the correct parameter names.
11. def process_data(data, max_length):
12. # …
13.
14. # Incorrect:
15. process_data(my_data, maximum_length=100) # maximum_length is wrong
16.
17. # Correct:
18. process_data(data=my_data, max_length=100)
Missing or Incorrectly Ordered Positional Arguments:
Problem: If a function requires positional arguments Before any keyword arguments, and you’re missing or have them in the wrong order, Python might misinterpret a keyword argument. Solution: Ensure that positional arguments are provided correctly and in the order defined by the function.
20. def create_user(username, password, is_admin=False):
21. print(f"Creating user: {username}")
22. # …
23.
24. # Incorrect (missing the positional username and password)
25. create_user(is_admin=True) # Results in a TypeError
26.
27. # Correct
28. create_user("john_doe", "password123", is_admin=True)
Incorrect Version of a Library or Module:
Problem: If you’re using a function from a third-party library, it’s possible that the function signature (the parameters it accepts) has changed in a newer version of the library.
Solution:
Check the Library’s Documentation: Consult the documentation for the version of the library you’re using to see the correct function parameters.
Update the Library: If appropriate, update to the latest version of the library (pip install —upgrade your_library). However, be aware that updating can sometimes introduce other compatibility issues, so test thoroughly.
Downgrade the Library: If you need to stick with a specific function signature, you might need to downgrade to an older version of the library (pip install your_library==specific_version).
Passing Arguments to a Class’s __init__ Method Incorrectly:
Problem: When creating an instance of a class, you pass arguments to the class’s __init__ method (the constructor). If you provide an incorrect keyword argument, you’ll get this error. Solution: Make sure the keyword arguments you’re using when creating the object match the parameters defined in the __init__ method.
31. class Dog:
32. def __init__(self, name, breed):
33. self. name = name
34. self. breed = breed
35.
36. # Incorrect:
37. my_dog = Dog(name="Buddy", type="Golden Retriever") # "type" is not a parameter in __init__
38.
39. # Correct:
40. my_dog = Dog(name="Buddy", breed="Golden Retriever")
Using **kwargs When It’s Not Needed or Is Incorrectly Used:
Problem: **kwargs allows a function to accept an arbitrary number of keyword arguments. If you’re Not using **kwargs in the function definition, you can’t pass arbitrary keyword arguments. Conversely, if **kwargs Is used, you should carefully examine how those keyword arguments are being handled Inside the function. Solution: If the function doesn’t use **kwargs, remove the extra keyword arguments from the function call. If it Does use **kwargs, make sure the function is correctly processing the arguments you’re passing.
42. def print_info(name, age):
43. print(f"Name: {name}, Age: {age}")
44.
45. # Incorrect:
46. print_info(name="Alice", age=30, city="New York") # city is unexpected
47.
48. def process_options(**kwargs):
49. for key, value in kwargs. items():
50. print(f"Option: {key} = {value}")
51.
52. process_options(color="red", size="large", quantity=10) # Correct, if process_options is designed to handle these.
Debugging Steps
Read the Error Message Carefully: The error message tells you Exactly which argument is the problem and which function is being called. Inspect the Function Definition: Use help(your_function) or look at the function’s source code to see its parameters. Print the Arguments: Temporarily add print statements to your function call to see the values and types of the arguments you’re passing. Use a Debugger: A debugger (like the one in VS Code, PyCharm, or pdb) allows you to step through your code line by line and inspect the values of variables. This can be very helpful in identifying the source of the error.
Example Scenario and Solution
Let’s say you have the following code and get the error:
Def display_message(text, font_size):
print(f"
{text}
")
Display_message("This is a message", fontsize=16)
The error would be:
TypeError: display_message() got an unexpected keyword argument ‘fontsize’
Solution: Notice the typo in the function call. It should be font_size, not fontsize.
Def display_message(text, font_size):
print(f"
{text}
")
Display_message("This is a message", font_size=16) # Corrected
By carefully checking the function definition and the arguments you’re passing, you can quickly find and fix this common Python error.