Using assignment as operator [duplicate]

Question

Consider:

course_db = Course(title='Databases')
course_db.save()

Coming from a C++ background, I would expect (course_db = Course(title='Databases')) to behave like it would in C++, that is, assign Course(title='Databases') to course_db and return the assigned object so that I can use it as part of a larger expression. For example, I would expect the following code to do the same thing as the code above:

(course_db = Course(title='Databases')).save()

This assumption got support from some quick Google searches using terms like "assignment operator in Python", e.g. this article. But when I tried this, I got a syntax error.

Why can't I do this in Python, and what can I do instead?

Answer 1

You should do some more research about the differences between statements and expressions in Python.

If you are using Python 3.8+, you can use the := operator:

In [1]: class A:
   ...:     def save(self):
   ...:         return 1
   ...: 

In [2]: (a := A()).save()
Out[2]: 1

In [3]: a
Out[3]: <__main__.A at 0x7f074e2ddaf0>