Bash ${var:-default} equivalent in Python?

Question

What's the simplest way to perform default variable substitution?

x = None
... (some process which may set x)
if x is None: use_x = "default"
else:         use_x = x

Is there any way of writing this in one line?

Answer 1

You can use a conditional expression:

use_x = "default" if x is None else x

You could use a dict defaulting to x if the key did not exist to resemble the bash syntax but the conditional would be the idiomatic way:

use_x = {None: "default"}.get(x, x)