Is there a way to improve this code to make it shorter?
if date_a is None and date_b is None and date_c is None:
start_date = current_date
else:
if date_a is not None:
start_date = date_a
elif date_b is not None:
start_date = date_b
elif date_c is not None:
start_date = date_c
You can use or, which will give you the first truthy value:
start_date = date_a or date_b or date_c or current_date
Another solution would be to turn them into an iterable, add an is None filter, and pull the first item using next():
start_date = next(date for date in (
date_a,
date_b,
date_c,
current_date
) if date is not None)
This approach works better if you need a condition other than "truthiness", or if you have a lot of values (in which case organizing them in an iterable container is likely easier than pasting them into a long or sequence).
As an alternative in Python >= 3.8 you can use an assignment expression plus any():
any(start_date := d for d in (date_a, date_b, date_c, current_date))
In your specific case I suspect that a chain of or would be faster, however any() will also work well if you have a collection of variables and not just single variables with different names:
any(start_date := d for d in dates)
The return value of any will let you know whether there was some truthy value or not.
(start_date := d for d in (date_a, date_b, date_c, current_date))
any will stop at the first item that is truthy, while what you wrote will simply go through all the elements and you will always end up with the last one being assigned to start_date after that statement.
any(start_date := d for d in (date_a, date_b, date_c, current_date)) should never pass any sane code reviewFirst, you can remove one if/else depth:
if date_a is not None:
start_date = date_a
elif date_b is not None:
start_date = date_b
elif date_c is not None:
start_date = date_c
else:
start_date = current_date
You could also take advantage of the for...else statement:
for start_date in (date_a, date_b, date_c):
if start_date is not None:
break
else:
start_date = current_date
The else only happens if none of the break conditions triggered, e.g. if all of the potential start_date's were None.
You can do something like:
start_date = date_a or date_b or date_c or current_date
Alternatively, there really is nothing wrong with:
if date_a is not None:
start_date = date_a
elif date_b is not None:
start_date = date_b
elif date_c is not None:
start_date = date_c
else:
start_date = current_date
start_date = date_a or date_b or date_c or current_datewould work, assuming that no possible value of these variables (other thanNone) is a "falsy" value (zero, empty string, empty container, etc.)