Menu
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?
863
The try block is used to check some code for errors i.e the code inside the try block will execute when there is no error in the program. Whereas the code inside the except block will execute whenever the program encounters some error in the preceding try block.
In Python, try and except are used to handle exceptions (= errors detected during execution). With try and except , even if an exception occurs, the process continues without terminating. You can use else and finally to set the ending process.
The try block lets you test a block of code for errors. The except block lets you handle the error. The else block lets you execute code when there is no error.
If you are going to print the exception, it is better to use print(repr(e)) ; the base Exception. __str__ implementation only returns the exception message, not the type. Or, use the traceback module, which has methods for printing the current exception, formatted, or the full traceback.
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:
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.
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.)
88
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 If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
