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Externe Quellen (nicht geprüft) Viele übersetzte Beispielsätze mit "exceptions apply" – Deutsch-Englisch Wörterbuch und Suchmaschine für Millionen von Deutsch-Übersetzungen.
22. Feb. 2017 · def convertToInt(cell): try: return int(cell) except: return None myDF['B'] = myDF['B'].apply(convertToInt) If I only do: myDF['B'].apply(int) the error obviously is: C:\WinPython-32bit-2.7.5.3\python-2.7.5\lib\site-packages\pandas\lib.pyd in pandas.lib.map_infer (pandas\lib.c:42840)()
- Overview
- Use try/catch/finally blocks to recover from errors or release resources
- Handle common conditions without throwing exceptions
- Design classes so that exceptions can be avoided
- Throw exceptions instead of returning an error code
- Use the predefined .NET exception types
- End exception class names with the word Exception
- Include three constructors in custom exception classes
- Ensure that exception data is available when code executes remotely
- Use grammatically correct error messages
A well-designed app handles exceptions and errors to prevent app crashes. This article describes best practices for handling and creating exceptions.
Use try/catch blocks around code that can potentially generate an exception, and your code can recover from that exception. In catch blocks, always order exceptions from the most derived to the least derived. All exceptions derive from the Exception class. More derived exceptions aren't handled by a catch clause that's preceded by a catch clause for a base exception class. When your code can't recover from an exception, don't catch that exception. Enable methods further up the call stack to recover if possible.
Clean up resources that are allocated with either using statements or finally blocks. Prefer using statements to automatically clean up resources when exceptions are thrown. Use finally blocks to clean up resources that don't implement IDisposable. Code in a finally clause is almost always executed even when exceptions are thrown.
For conditions that are likely to occur but might trigger an exception, consider handling them in a way that will avoid the exception. For example, if you try to close a connection that's already closed, you'll get an InvalidOperationException. You can avoid that by using an if statement to check the connection state before trying to close it. if (conn.State != ConnectionState.Closed) { conn.Close(); } If you don't check the connection state before closing, you can catch the InvalidOperationException exception. try { conn.Close(); } catch (InvalidOperationException ex) { Console.WriteLine(ex.GetType().FullName); Console.WriteLine(ex.Message); } The method to choose depends on how often you expect the event to occur.
•Use exception handling if the event doesn't occur often, that is, if the event is truly exceptional and indicates an error, such as an unexpected end-of-file. When you use exception handling, less code is executed in normal conditions.
A class can provide methods or properties that enable you to avoid making a call that would trigger an exception. For example, a FileStream class provides methods that help determine whether the end of the file has been reached. These methods can be used to avoid the exception that's thrown if you read past the end of the file. The following example shows how to read to the end of a file without triggering an exception: class FileRead { public void ReadAll(FileStream fileToRead) { // This if statement is optional // as it is very unlikely that // the stream would ever be null. if (fileToRead == null) { throw new ArgumentNullException(); } int b; // Set the stream position to the beginning of the file. fileToRead.Seek(0, SeekOrigin.Begin); // Read each byte to the end of the file. for (int i = 0; i < fileToRead.Length; i++) { b = fileToRead.ReadByte(); Console.Write(b.ToString()); // Or do something else with the byte. } } } Another way to avoid exceptions is to return null (or default) for most common error cases instead of throwing an exception. A common error case can be considered a normal flow of control. By returning null (or default) in these cases, you minimize the performance impact to an app.
For value types, whether to use Nullable or default as your error indicator is something to consider for your app. By using Nullable , default becomes null instead of Guid.Empty. Sometimes, adding Nullable can make it clearer when a value is present or absent. Other times, adding Nullable can create extra cases to check that aren't necessary and only serve to create potential sources of errors.
Exceptions ensure that failures don't go unnoticed because the calling code didn't check a return code.
Introduce a new exception class only when a predefined one doesn't apply. For example:
•If a property set or method call isn't appropriate given the object's current state, throw an InvalidOperationException exception.
When a custom exception is necessary, name it appropriately and derive it from the Exception class. For example: public class MyFileNotFoundException : Exception { }
Use at least the three common constructors when creating your own exception classes: the parameterless constructor, a constructor that takes a string message, and a constructor that takes a string message and an inner exception.
•Exception(), which uses default values.
•Exception(String), which accepts a string message.
•Exception(String, Exception), which accepts a string message and an inner exception.
When you create user-defined exceptions, ensure that the metadata for the exceptions is available to code that's executing remotely.
For example, on .NET implementations that support app domains, exceptions might occur across app domains. Suppose app domain A creates app domain B, which executes code that throws an exception. For app domain A to properly catch and handle the exception, it must be able to find the assembly that contains the exception thrown by app domain B. If app domain B throws an exception that is contained in an assembly under its application base, but not under app domain A's application base, app domain A won't be able to find the exception, and the common language runtime will throw a FileNotFoundException exception. To avoid this situation, you can deploy the assembly that contains the exception information in either of two ways:
•Put the assembly into a common application base shared by both app domains.
•If the domains don't share a common application base, sign the assembly that contains the exception information with a strong name and deploy the assembly into the global assembly cache.
Write clear sentences and include ending punctuation. Each sentence in the string assigned to the Exception.Message property should end in a period. For example, "The log table has overflowed." would be an appropriate message string.
24. Juli 2023 · Checked Exceptions are the exceptions that we can typically foresee and plan ahead in our application. These are also exceptions that the Java Compiler requires us to either handle-or-declare when writing code.
22. Apr. 2023 · Exceptions are types that all ultimately derive from System.Exception. Use a try block around the statements that might throw exceptions. Once an exception occurs in the try block, the flow of control jumps to the first associated exception handler that is present anywhere in the call stack.
15. Nov. 2017 · 1 Answer. Sorted by: 2. It means that some people are excluded from this offer. When a company makes a special offer, such as "Enter a code on our website to get a discount", they might want to exclude some people. For example, they might exclude people who work at the company, or they might exclude business users of the service.
24. Sept. 2022 · An exception is an error that occurs during the execution of a program that disrupts its normal control flow or execution. Examples include invalid user input, unavailable resources like files and folders, and trying to access elements of arrays in a non-existent index.
