I have this try block in my code: Strictly speaking, I am actually raising another ValueError, not the ValueError thrown by do_something…(), which is referred to as err in this case. How do I attach a custom message to err? I try the following code but fails due to err, a ValueError instance, not being callable: Answer Update: For Python
Tag: exception
Logging uncaught exceptions in Python
How do you cause uncaught exceptions to output via the logging module rather than to stderr? I realize the best way to do this would be: But my situation is such that it would be really nice if logging.exception(…) were invoked automatically whenever an exception isn’t caught. Answer As Ned pointed out, sys.excepthook is invoked every time an exception is
What is the use of “assert” in Python?
What does assert mean? How is it used? Answer The assert statement exists in almost every programming language. It has two main uses: It helps detect problems early in your program, where the cause is clear, rather than later when some other operation fails. A type error in Python, for example, can go through several layers of code before actually
Why doesn’t list have safe “get” method like dictionary?
Why doesn’t list have a safe “get” method like dictionary? Answer Ultimately it probably doesn’t have a safe .get method because a dict is an associative collection (values are associated with names) where it is inefficient to check if a key is present (and return its value) without throwing an exception, while it is super trivial to avoid exceptions accessing
How can I write a `try`/`except` block that catches all exceptions?
How can I write a try/except block that catches all exceptions? Answer You can but you probably shouldn’t: However, this will also catch exceptions like KeyboardInterrupt and you usually don’t want that, do you? Unless you re-raise the exception right away – see the following example from the docs:
How to check that a regular expression has matched a string completely, i.e. – the string did not contain any extra character?
I have two questions: 1) I have a regular expression ([A-Z][a-z]{0,2})(d*) and I am using Python’s re.finditer() to match appropriate strings. My problem is, that I want to match only strings that contain no extra characters, otherwise I want to raise an exception. I want to catch a following pattern: – capital letter, followed by 0, 1 or 2 small
How to handle exceptions in a list comprehensions?
I have some a list comprehension in Python in which each iteration can throw an exception. For instance, if I have: I’ll get a ZeroDivisionError exception in the 3rd element. How can I handle this exception and continue execution of the list comprehension? The only way I can think of is to use a helper function: But this looks a