"SyntaxError: Positional Argument Follows Keyword Argument" in Python

Introduction

Python is a very easy programming language and its syntax is not complicated. At the same time, it's praised by novices as well as old school programmers. But, similar to any other language Python as well has its quirks and often enough developers find themselves faced with errors while working through their development process. One such error that can be perplexing is the "SyntaxError: In this article, we will try to explain in what way such problems as "positional argument follows keyword argument" occur.

Understanding the Error

1. Definition

The SyntaxError: It is a runtime error where positional arguments intervene keyword ones in the calling regulations of functions.

Example 1:

Output:

ERROR!
File "", line 9
    foo(a=2, c=3, 9) 
                   ^
SyntaxError: positional argument follows keyword argument

Explanation:

It appears there is a syntax issue with the function call. The correct syntax for calling the function with both positional and keyword arguments should be:

Let's break down the correction:

• 2 is the positional argument for parameter a.
• 1 keyword argument 'b=9' assigns explicitly the value of '9' to associated parameter.
• The keyword argument c=3 assigns the value 3 to the parameter.
• Here's the corrected code:

Corrected Code:

Output:

Corrected Function Call
a = 2
b = 9
c = 3

Example 2:

Output:

ERROR!
File "", line 1
    def example_function(arg1, kwarg1='default_value', arg2):
                                                       ^^^^
SyntaxError: positional argument follows keyword argument

Explanation

In this snippet, the function 'example_function' has a positional argument 'arg2' following a keyword argument 'kwarg1', resulting in the "SyntaxError: positional argument follows keyword argument."

Resolving the Error

To fix the SyntaxError: positional argument follows keyword argument.

1. Correct Argument Order

Make sure your function calls maintain the right sequence of arguments. Precedence should be given to positional arguments over keyword ones. In the example above, the function call should be corrected as follows:

2. Check Function Definition

First, make sure to double-check the function definition to ensure it matches the order of parameters passed in your function calls. If necessary, modify the function definition to maintain consistency:

3. Review Documentation

Read the documentation when you use third-party libraries to see how arguments should be placed in order for functions that are used correctly. There may be some special requirements or limitations in certain libraries.

4. Update to Latest Version

If you're working with a library and the problem remains, update to the latest version. Bug fixes and enhancements are periodically provided, or the problem could have been resolved in a more recent release.

Deeper Dive into Positional and Keyword Arguments

1. Positional Arguments

In Python, arguments are typically passed to functions in two ways: positional and keyword. The simplest is positional arguments - they are assigned according to the order in which function appears during definition and calls.

2. Keyword Arguments

On the other hand, keyword arguments are assigned values using the parameter names. This enables for a more clear allocation and is especially useful where there are many parameters in the functions.

3. Combining Both

When calling a function in Python, developers have the option to use both positional and keyword arguments; however, it is essential to arrange them accurately. Mixing them incorrectly can lead to the "SyntaxError: positional argument follows keyword argument."

Common Scenarios Leading to the Error

1. Function Signature Mismatch: Morning, this error normally happens as a result of incompatibility between the function definition and the call to such that. When the order of arguments in the call doesn't align with the definition, Python raises the "SyntaxError: positional argument follows keyword argument."
2. Third-Party Libraries: Particularly while working with libraries especially those of complicated functions, it is necessary to take the documentation closely. This coding error occurs when arguments are not used properly.
3. Code Refactoring: This error may occur when developers refactor or edit the code accidentally changing the order of arguments. Such problems can be caught early during the development process if regular code reviews and testing processes are followed.

Best Practices to Avoid the Error

1. Consistency is Key: Consistently order of arguments across function definitions and calls. This not only helps to prevent syntax errors but also improves code readability.
2. Thorough Documentation: Documenting your code, such as function signatures and expected argument orders can be a big help. It is used by current and future developers working on the codebase as a reference.
3. Testing and Code Reviews: Implement rigorous testing mechanisms such as unit test for functions having several parameters. Besides that, timely code inspections can also allow correcting errors early in the development process.

Conclusion

In the Python development, one is bound to meet errors. The "SyntaxError: Developers should not fall into the stumbling block of "positional argument follows keyword argument" because its causes and solutions are clear to them. ensure a consistent ordering of arguments, read documentation carefully to avoid misunderstandings and use testing and peer code reviews whenever possible in order not to miss any mistakes early on. By using best practices and adopting a forward-thinking approach to problem resolution, Python developers can guarantee the stability and reliability of their code.