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try {// Normal execution path. throw new EmptyStackException ();} catch (ExampleException ee) {// Deal with the ExampleException.} finally {// Always run when leaving the try block (including finally clauses), regardless of whether any exceptions were thrown or whether they were handled. // Cleans up and closes resources acquired in the try block.
It is possible to use a single try...finally block even when dealing with multiple resources, but that requires a correct use of sentinel values, which is another common source of bugs for this type of problem. [13]: 8:6–8:7 Python and Ruby also permit a clause (else) that is used in case no exception occurred before the end of the handler's ...
In Object Pascal, D, Java, C#, and Python a finally clause can be added to the try construct. No matter how control leaves the try the code inside the finally clause is guaranteed to execute. This is useful when writing code that must relinquish an expensive resource (such as an opened file or a database connection) when finished processing:
«Finally instructions» End Try: System.Diagnostics.Debug.Assert(condition) or System.Diagnostics.Trace.Assert(condition) Xojo: Raise exception: Try instructions Catch «exception» instructions... «Finally instructions» End Try — Python: raise exception: try: Tab ↹instructions except «exception»: Tab ↹instructions... «else: Tab ↹ ...
In Python, functions are first-class objects that can be created and passed around dynamically. Python's limited support for anonymous functions is the lambda construct. An example is the anonymous function which squares its input, called with the argument of 5:
If-then-else flow diagram A nested if–then–else flow diagram. In computer science, conditionals (that is, conditional statements, conditional expressions and conditional constructs) are programming language constructs that perform different computations or actions or return different values depending on the value of a Boolean expression, called a condition.
In Python 3.x the range() function [28] returns a generator which computes elements of the list on demand. Elements are only generated when they are needed (e.g., when print(r[3]) is evaluated in the following example), so this is an example of lazy or deferred evaluation: >>>
The dangling else is a problem in programming of parser generators in which an optional else clause in an if–then(–else) statement can make nested conditional statements ambiguous. Formally, the reference context-free grammar of the language is ambiguous , meaning there is more than one correct parse tree .