Python: try-except as an Expression?

Question

I find myself having this sort of pattern over and over:

variable = "" try:     variable = ... do some file loading stuff ... except:     variable = "" 

Is there any way to condense this into a single expression? Like with if-else statements you can turn:

variable = "" if something:     variable = somethingelse else:     variable = "" 

into

variable = somethingelse if something else "" 

Is there any equivalent thing for try-catch?

Answer 1

Since agf already provided the approach I'd recommend, here's a version of his routine with a couple of minor enhancements:

def try_except(success, failure, *exceptions):     try:         return success()     except exceptions or Exception:         return failure() if callable(failure) else failure 

This version:

1. Lets you specify exactly which exceptions will be caught as additional optional arguments. You should always catch the minimum set of exceptions that will do the job and let exceptions you can't handle bubble up to the caller.

2. Supports the use of a plain value as well as a function for the failure value. This saves you having to use a lambda in a lot of cases. (Of course, instead of lambda: '' you can just use str.)

Answer 2

def try_except(success, failure):     try:         return success()     except:         return failure()  variable = try_except(do_some_file_loading_stuff, lambda: '') 

I think the code is self explanatory. It returns the value returned by success unless there is an error, then it returns the value returned by failure. If do_some_file_loading_stuff is an expression rather than just a function call, wrap it in a lambda as well.

Edit: @kindall and I improved his version a bit so it's just as fast as mine, can be called exactly the same if you want, has more features, and is the same number of lines. Use it!

def try_except(success, failure, *exceptions):     try:         return success()     except exceptions or Exception:         return failure() if callable(failure) else failure