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Positional and Keyword Arguments in Python

In Python, functions can accept arguments in two ways: positional arguments and keyword arguments. Positional arguments are passed based on their position in the function call, while keyword arguments are passed with a name-value pair. In this tutorial, we will discuss positional and keyword arguments, their usage, and possible errors you may encounter while using them effectively.

Positional Arguments

Positional arguments are the most basic way of passing arguments to a function. They are passed in the order specified by the function's parameter list.

def greet(name, age):
    print("Hello", name, "!")
    print("You are", age, "years old.")

greet("Nisha", 16)

Output

Hello Nisha !
You are 16 years old.

Positional arguments are suitable for scenarios where the number of arguments is small and known in advance. They are used when the order of the arguments is significant and remains consistent across different function calls.

Possible Errors:

  • Missing Arguments: Providing fewer arguments than expected will result in a TypeError.
  • Incorrect Order: Swapping the order of arguments can lead to incorrect results or unexpected behavior.

Keyword Arguments

Keyword arguments are passed with a name-value pair, allowing you to specify the argument's name when calling the function.

def greet(name, age):
    print("Hello", name, "!")
    print("You are", age, "years old.")

greet(name="Aman", age=17)

Output

Hello Aman !
You are 17 years old.

Keyword arguments are useful when the order of the arguments is not important, and you want to make the function call more readable and self-explanatory. They are handy when you have functions with a large number of parameters, and you want to selectively specify values for specific parameters.

Possible Errors:

  • Unknown Keyword Arguments: Providing a keyword argument that doesn't match any parameter in the function definition will result in a TypeError.
  • Duplicate Keyword Arguments: Passing the same keyword argument multiple times will raise a TypeError.

Mixing Positional and Keyword Arguments

Python allows you to mix positional and keyword arguments in function calls.

def greet(name, age):
    print("Hello", name, "!")
    print("You are", age, "years old.")

greet("Alice", age=18)

Output

Hello Alice !
You are 18 years old.

Mixing positional and keyword arguments can provide more clarity and flexibility when calling functions with multiple arguments.

Possible Errors:

  • Duplicate Arguments: Providing the same argument both as a positional argument and a keyword argument can lead to a TypeError.
  • Incorrect Ordering: Placing keyword arguments before positional arguments can result in a SyntaxError.

Understanding the usage of positional and keyword arguments in Python is crucial for writing flexible and reusable code. Positional arguments are suitable when the order matters, while keyword arguments provide more readability and flexibility. Mixing positional and keyword arguments can enhance clarity. Being aware of the possible errors associated with each argument type is important to avoid mistakes and ensure the correct functioning of your code.


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