Python Variable Assignment If Variable Exists else None in One Line

Question

Can this be done in one line? Something that looks like this data['x'] = (x if x else "") (except doesn't raise an exception)

Otherwise I often end up doing the following:

try: data['x'] = x
except: data['x'] = ""

or for multiple keys initializing with empty values: i.e.

data['x'], data['y'] = [], []

Why would data['x'] = x raise an exception? You mean x might not be set? Generally, you'd avoid that kind of situation. — Martijn Pieters
– Martijn Pieters, Commented Jun 19, 2014 at 18:04
@AdamWagner: yeah, I see that. A case of why not just set x = '' and be done with it. — Martijn Pieters
– Martijn Pieters, Commented Jun 19, 2014 at 18:05
@user3467349, you should generally know if a var exists. And as Martjin points out, you could just set the value ahead of time to some default value, so you don't get an exception. — Adam Wagner
– Adam Wagner, Commented Jun 19, 2014 at 18:07

Dologan · Accepted Answer · 2014-06-19 18:11:34Z

2

As others have pointed out on comments, using probably unset variables is poor form, but if you insist, Luis Masuelli's comment should do the trick:

data['x'] = locals().get('x','')  # or globals, depending on the scope you need

answered Jun 19, 2014 at 18:11

Dologan

4,8342 gold badges35 silver badges33 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

I don't see the reason for generalizing 'all possible use cases' to poor form. But that does work, thanks.

Sure, there are exceptions to everything, but generally it would suggest a flawed design somewhere on the line.