Positional argument follows keyword argument как исправить

In this article, we will discuss how to fix the syntax error that is positional argument follows keyword argument in Python

An argument is a value provided to a function when you call that function. For example, look at the below program –

The calculate_square() function takes in an argument num which is an integer or decimal input, calculates the square of the number and returns the value.

Keyword and Positional Arguments in Python

There are two kind of arguments, namely, keyword and positional. As the name suggests, the keyword argument is identified by a function based on some key whereas the positional argument is identified based on its position in the function definition. Let us have a look at this with an example.

Output:

Function Call 1
a = 2
b = 3
c = 8
Function Call 2
a = 2
b = 3
c = 10
Function Call 3
a = 2
b = 10
c = 3

Explanation:

1. During the first function call, we provided 3 arguments with any keyword. Python interpreted in order of how they have been defined in the function that is considering position of these keywords.
2. In the second function call, we provided 2 arguments, but still the output is shown because of we provided 2 positional argument and the function has a default value for the final argument c. So, it takes the default value into account for the final argument.
3. In the third function call, three keyword arguments are provided. The benefit of providing this keyword argument is that you need not remember the positions but just the keywords that are required for the function call. These keywords can be provided in any order but function will take these as key-value pairs and not in the order which they are being passed.

SyntaxError: positional argument follows keyword argument

In the above 3 cases, we have seen how python can interpret the argument values that are being passed during a function call. Now, let us consider the below example which leads to a SyntaxError.

Output:

File "<ipython-input-40-982df054f26b>", line 7
    foo(a=2, c=3, 9)
                 ^
SyntaxError: positional argument follows keyword argument

Explanation:

In this example, the error occurred because of the way we have passed the arguments during the function call. The error positional argument follows keyword argument means that the if any keyword argument is used in the function call then it should always be followed by keyword arguments. Positional arguments can be written in the beginning before any keyword argument is passed. Here, a=2 and c=3 are keyword argument. The 3rd argument 9 is a positional argument. This can not be interpreted by the python as to which key holds what value. The way python works in this regards is that, it will first map the positional argument and then any keyword argument if present.

How to avoid the error – Conclusion

Last Updated :
28 Nov, 2021

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If you provide the keyword argument first followed by a positional argument, the Python interpreter will raise SyntaxError: positional argument follows keyword argument.

In this tutorial, we will learn what SyntaxError: positional argument follows keyword argument means and how to resolve this error with examples.

An argument is a variable, value, or object passed to a method or function as an input. We have two types of arguments in Python, and we can pass these arguments while calling the methods.

Positional Argument -The positional arguments are the one that does not have any keyword in front of them.

Example

result = add_numbers(10, 20, 30)

Keyword Argument -The Keyword arguments are the one that has a keyword in front of them.

Example

result = add_numbers(a=10, b=20, c=30)

Every programming language has its own set of rules. These rules are referred to as the syntax that needs to be followed while programming.

The positional and keyword arguments must appear in a specific order; otherwise, the Python interpreter will throw a Syntax error.

The Python rule says positional arguments must appear first, followed by the keyword arguments if we are using it together to call the method.

The SyntaxError: positional argument follows keyword argument means we have failed to follow the rules of Python while writing a code.

Let us take a simple example to demonstrate this error.

# Method that takes 3 arguments and returns sum of it
def add_numbers(a, b, c):
    return a+b+c

# call the method by passing the arguments
result = add_numbers(a=10, 20, 30)

# print the output
print("Addition of numbers is", result)

Output

  File "c:PersonalIJSCodemain.py", line 8
    result = add_numbers(a=10, 20, 30)
                                     ^
SyntaxError: positional argument follows keyword argument

We have passed the Keyword argument first in the above code and then followed by the Positional argument which breaks the rule and hence we get the SyntaxError.

How to fix SyntaxError: positional argument follows keyword argument?

There are several ways to fix the error. Let us look at all the correct ways to call the methods in Python.

Scenario 1 – Use only Positional Arguments.

The easier way to fix the issue is to use only Positional arguments while calling the method in Python.

Let us fix our example by passing only positional arguments and see what happens when we run the code.

# Method that takes 3 arguments and returns sum of it
def add_numbers(a, b, c):
    return a+b+c

# call the method by passing only positional arguments
result = add_numbers(10, 20, 30)

# print the output
print("Addition of numbers is", result)

Output

Addition of numbers is 60

The code runs without any error as Python knows which values to use for each argument in the function.

Scenario 2 – Use only Keyword Arguments.

Another way to resolve the error is to use only the Keyword arguments while calling the method in Python.

# Method that takes 3 arguments and returns sum of it
def add_numbers(a, b, c):
    return a+b+c


# call the method by passing only keyword arguments
result = add_numbers(a=10, b=20, c=30)

# print the output
print("Addition of numbers is", result)

Output

Addition of numbers is 60

The code runs without any error as Python knows which values to use for each argument in the function.

Scenario 3 – Use Positional arguments first, followed by Keyword Arguments.

If you need to use both positional and keyword arguments, you need to abide by the rules of Python.

The Positional arguments should always appear first, followed by the keyword arguments.

In the below example, we have fixed the issue by passing the two positional arguments first and then a keyword argument.

# Method that takes 3 arguments and returns sum of it
def add_numbers(a, b, c):
    return a+b+c


# pass all positional arguments first and then keyword arguments
result = add_numbers(10, 20, c=30)

# print the output
print("Addition of numbers is", result)

Output

Addition of numbers is 60

Conclusion

In Python, the SyntaxError: positional argument follows keyword argument occurs if you pass keyword arguments before the positional arguments. Since Python interprets positional arguments in the order in which they appear first and then followed by the keyword arguments as next.

We can resolve the SyntaxError by providing all the positional arguments first, followed by the keyword arguments at last.