Question

For example, in the code below I would like to obtain the list [1,2,3] using x as a reference.

In[1]: pasta=[1,2,3]
In:[2]: pasta
Out[2]: [1, 2, 3]
In [3]: x='pas'+'ta'
In [4]: x
Out[4]: 'pasta'

Answer 1

What you are trying to do is a bad practice.

What you really need is a dict:

>>> dct = {'pasta': [1,2,3]}
>>> x = 'pas' + 'ta'
>>> dct[x]
[1, 2, 3]

This is the right data structure for the actual task you’re trying to achieve: using a string to access an object.

Other answers suggested (or just showed with a worning) different ways to do that. Since Python is a very flexible language, you can almost always found such different ways to follow for a given task, but “there should be one– and preferably only one –obvious way to do it”^[1].

All of them will do the work, but not without downsides:

• locals() is less readable, needlessly complex and also open to risks in some cases (see Mark Byers answer). If you use locals() you are going to mix the real variables with the database ones, it’s messy.
• eval() is plain ugly, is a “quick-and-dirty way to get some source code dynamically”^[2] and a bad practice.

When in doubt about the right way to choose, tring to follow the Zen of Python might be a start.

And hey, even the InteractiveInterpreter could be used to access an object using a string, but that doesn’t mean I’m going to.