SyntaxError: non-default argument follows default argument in Python

Dung Do Tien Jun 22 2022 17

Hi everyone, I am a beginner in Python and today I am learning about methods and arrays. I wrote some code as below:

 def add_book(name, author, price = 0, publish_date):
    return {'name': name, 'author': author, 'price': price, 'publish_date': publish_date}

store = []
store.append(add_book('Book 1', 'A', 100, "2022/01/10"))
store.append(add_book('Book 2', 'A', 130, "2022/03/10"))
store.append(add_book('Book 3', 'B', 170, "2022/03/10"))
for x in store:
  print(x)

I create a method name add_book() that helps return a dictionary and I will add it to an array. But when I ran the code above I got an exception SyntaxError: non-default argument follows default argument.

 File "main.py", line 1
    def add_book(name, author, price = 0, publish_date):
                 ^
SyntaxError: non-default argument follows default argument

I'm using Python version 3.9.8 and Windows 11.

I appreciate your help.

Have 1 answer(s) found.
  • r

    raphael seban Jun 22 2022

    The error SyntaxError: non-default argument follows default argument is a compile error, you are wrong syntax.

    Theory about method's param: Optional parameters have to appear behind non-optional parameters.

     your price parameter is an optional parameter so it should be moved to the last. See the code below:

     def add_book(name, author, publish_date, price = 0):
        return {'name': name, 'author': author, 'price': price, 'publish_date': publish_date}
    
    store = []
    store.append(add_book('Book 1', 'A', "2022/01/10"))
    store.append(add_book('Book 2', 'A', "2022/03/10", 200))
    store.append(add_book('Book 3', 'B', "2022/03/10", 110))
    for x in store:
      print(x)

    #Output

     {'name': 'Book 1', 'author': 'A', 'price': 0, 'publish_date': '2022/01/10'}
    {'name': 'Book 2', 'author': 'A', 'price': 200, 'publish_date': '2022/03/10'}
    {'name': 'Book 3', 'author': 'B', 'price': 110, 'publish_date': '2022/03/10'}

    I hope this answer is helpful to you.

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