[FIXED] How can I merge two argparse Namespaces in Python 2.x?

Issue

I want to merge 2 argparse.Namespace objects in Python 2.x.

In python 3.x I can do something like this:

from argparse import Namespace

# The 2 initial objects
options_foo = Namespace(foo="foo")
options_bar = Namespace(bar="bar")

# the merged object
options_baz = Namespace(**vars(options_foo), **vars(options_bar))

And get:

print(options_baz)
# Namespace(foo="foo", bar="bar")

But in python 2.x I can't. I get the following error.

SyntaxError: invalid syntax

Is there an easy way to achieve this?

Solution

I've majorly reconsidered this answer, because I didn't fully read and understand your problem...

It's true that this line is valid in Python3, and invalid in Python2:

options_baz = Namespace(**vars(options_foo), **vars(options_bar))

When we look at the error, we see that it's the comma (,) that Python2 cannot accept:

  File "main.py", line 8
    options_baz = Namespace(**vars(options_foo), **vars(options_bar))
                                               ^
SyntaxError: invalid syntax

So, let's just avoid passing two sets of options to the Namespace() initializer:

...

dict_baz = vars(options_foo)
dict_baz.update(vars(options_bar))

# the merged object
options_baz = Namespace(**dict_baz)

print(options_baz)

and we get:

Namespace(bar='bar', foo='foo')

In another answer you pointed out that the double-star (**) syntax is invalid, but that's definitely valid syntax. We can see it mentioned as far back as Python 2.2:

If the syntax **expression appears in the function call, expression must evaluate to a (subclass of) dictionary, ...

It was just that comma all along.

Answered By - Zach Young