How to Print Error in Catch

How do I print an exception in Python?

For Python 2.6 and later and Python 3.x:

except Exception as e: print(e)

For Python 2.5 and earlier, use:

except Exception,e: print str(e)

How to print a message in error handling with try, catch

This will help:

var x = { asd: "asd", };

try {
    JSON.parse(x);
}
catch (e) {
    console.log("Error", e.stack);
    console.log("Error", e.name);
    console.log("Error", e.message);
}

error.stack is not exactly what you want, but it will help you.

How to print details of a 'catch all' exception in Swift?

I just figured it out. I noticed this line in the Swift Documentation:

If a catch clause does not specify a pattern, the clause will match and bind any error to a local constant named error

So, then I tried this:

do {
    try vend(itemNamed: "Candy Bar")
...
} catch {
    print("Error info: \(error)")
}

And it gave me a nice description.

Display Exception on try-catch clause

You can use .Message, however I wouldn't recommend just catching Exception directly. Try catching multiple exceptions or explicitly state the exception and tailor the error message to the Exception type.

try 
{
   // Operations
} 
catch (ArgumentOutOfRangeException ex) 
{
   MessageBox.Show("The argument is out of range, please specify a valid argument");
}

Catching Exception is rather generic and can be deemed bad practice, as it maybe hiding bugs in your application.

You can also check the exception type and handle it accordingly by checking the Exception type:

try
{

} 
catch (Exception e) 
{
   if (e is ArgumentOutOfRangeException) 
   { 
      MessageBox.Show("Argument is out of range");
   } 
   else if (e is FormatException) 
   { 
      MessageBox.Show("Format Exception");
   } 
   else 
   {
      throw;
   }
}

Which would show a message box to the user if the Exception is an ArgumentOutOfRange or FormatException, otherwise it will rethrow the Exception (And keep the original stack trace).

How to print an exception in Python 3?

I'm guessing that you need to assign the Exception to a variable. As shown in the Python 3 tutorial:

def fails():
    x = 1 / 0

try:
    fails()
except Exception as ex:
    print(ex)

To give a brief explanation, as is a pseudo-assignment keyword used in certain compound statements to assign or alias the preceding statement to a variable.

In this case, as assigns the caught exception to a variable allowing for information about the exception to stored and used later, instead of needing to be dealt with immediately.

(This is discussed in detail in the Python 3 Language Reference: The try Statement.)

---

There are other compound statements that use as. The first is the with statement:

@contextmanager
def opening(filename):
    f = open(filename)
    try:
        yield f
    finally:
        f.close()

with opening(filename) as f:
    # ...read data from f...

Here, with statements are used to wrap the execution of a block with methods defined by context managers. This functions like an extended try...except...finally statement in a neat generator package, and the as statement assigns the generator-produced result from the context manager to a variable for extended use.

(This is discussed in detail in the Python 3 Language Reference: The with Statement.)

---

As of Python 3.10, match statements also use as:

from random import randint

match randint(0, 2):
    case 0|1 as low:
        print(f"{low} is a low number")
    case _:
        print("not a low number")

match statements take an expression (in this case, randint(0, 2)) and compare its value to each case branch one at a time until one of them succeeds, at which point it executes that branch's block. In a case branch, as can be used to assign the value of the branch to a variable if that branch succeeds. If it doesn't succeed, it is not bound.

(The match statement is covered by the tutorial and discussed in detail in the Python 3 Language Reference: match Statements.)

---

Finally, as can be used when importing modules, to alias a module to a different (usually shorter) name:

import foo.bar.baz as fbb

This is discussed in detail in the Python 3 Language Reference: The import Statement.

how to print error in catch

The catch blocks are exclusive cases, evaluated in order. When a match succeeds, we stop.

So, let's just think about this structure:

catch LocksmithError.Duplicate {
    // 1
    print("duplicate")
}
catch {
    // 2
    print(error)
}

If we are at 1, then what is in scope is the LocksmithError.Duplicate.

If we are at 2, then what is in scope is every other kind of error that gets caught. There's no way you can get hold of the LocksmithError.Duplicate here, because ex hypothesi it would have been caught in 1 and we wouldn't be here.

Now, the way I would do it is like this:

catch let err as LocksmithError {
    // 1
    print(err)
}
catch {
    // 2
    print(error)
}

That may be the sort of thing you are after; it gives us a value err that carries the error into the curly braces in 1. (The automatic error value exists only the final catch-all catch block.)

How to catch exception in flutter?

Try

void loginUser(String email, String password) async {
  try {
    var user = await _data
      .userLogin(email, password);
    _view.onLoginComplete(user);
      });
  } on FetchDataException catch(e) {
    print('error caught: $e');
    _view.onLoginError();
  }
}

catchError is sometimes a bit tricky to get right.
With async/await you can use try/catch like with sync code and it is usually much easier to get right.

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