How to use multiple return values functions in this particular way?

Question

I have a function that returns two values:

def dbfunc:
  # ...
  return var1, var2

I have this class:

class MyClass:
  foo = ...
  bar = ...

I'd like to assign the result of dbfunc() to the MyClass instance I'm trying to create. I'd tried this:

my_object = MyClass(dbfunc()) # does not work because the return type is a tuple

I could do this:

res = dbfunc()
my_object = MyClass(foo=res[0], bar=res[1])

but I'm actually trying to do this in a middle of a comprehensive list so I can not make these kind of "pre-affectations". I have to do it in one time.

Thanks for help.

score 3 · Accepted Answer · edited May 23 '17 at 11:49

Argument unpacking:

my_object = MyClass(*dbfunc())

Put a * before the last argument to a function, and Python will iterate over that argument and pass the elements to the function as separate positional arguments. You can use ** with a dict for keyword arguments.

Also, it looks like you may have a bug regarding class vs. instance attributes. See "How do I avoid having Python class data shared among instances?". It might or might not be fine, depending on the parts of MyClass you stripped out.

score 0 · Answer 2 · answered Feb 18 '14 at 19:16

You can define more simply your function and your class I think as shown below.

def dbfunc:
    # ...
    return var1, var2

class MyClass:
    def __init__(foo, bar):
        self.foo = name
        self.bar = bar

[var1, var2] = dbfunc()
my_object = MyClass(var1, var2)

How to use multiple return values functions in this particular way?

2 Answers2