Name of type of object

[Jive Dadson]

The traceback routine prints out stuff like,

NameError: global name 'foo' is not defined

NameError is a standard exception type.

What if I want to print out something like that?
I've determined that "global name 'foo' is not defined" comes
from the __str__ member of the exception object.
Where does it find the string "NameError"? In general, if I have
an object, is there a way to obtain the name of the type of the object?

Thankee.

 

[Randall Smith]

The traceback routine prints out stuff like,

NameError: global name 'foo' is not defined

NameError is a standard exception type.

What if I want to print out something like that?
I've determined that "global name 'foo' is not defined" comes
from the __str__ member of the exception object.
Where does it find the string "NameError"? In general, if I have
an object, is there a way to obtain the name of the type of the object?

Thankee.

type(object) ?

Randall

 

[Steven Bethard]

type(object) ?

Doesn't work for old-style classes like exceptions:

py> e = NameError("global name 'foo' is not defined")
py> type(e)
<type 'instance'>
py> type(e).__name__
'instance'

For old-style classes, you'll need to go through __class__

py> e.__class__
<class exceptions.NameError at 0x00934900>
py> e.__class__.__name__
'NameError'

STeVe

 

[George Sakkis]

Doesn't work for old-style classes like exceptions:

py> e = NameError("global name 'foo' is not defined")
py> type(e)
<type 'instance'>
py> type(e).__name__
'instance'

For old-style classes, you'll need to go through __class__

py> e.__class__
<class exceptions.NameError at 0x00934900>
py> e.__class__.__name__
'NameError'

STeVe

To sum up:

def typename(obj):
try:
return obj.__class__.__name__
except AttributeError:
return type(obj).__name__


George

 

[Jive Dadson]

I don't think I've quite got it.

The application I'm writing has some similarities to an interactive
shell. Like an interactive shell, it executes arbitrary code that it
receives from an input stream. When it gets an exception, it should
create an informative message, regardless of the type of exception. The
traceback routine does that, somehow, some way, but I've tried to read
that code and figure out how and I don't get it.

The best I have so far is,

class Exec_thread(BG_thread):
""" Execute a line of code in the global namespace. """
def _process(s):
""" Process one instruction """
try:
exec s.product in globals()
except (Exception), e:
handle_error( typename(e)+ ": " + str(e) )


But that works only if the exception happens to be derived from
Exception. How do I handle the
general case?

 

[Jeremy Bowers]

But that works only if the exception happens to be derived from Exception.
How do I handle the
general case?

I believe the answer is that Exceptions not derived from Exception
shouldn't be thrown; it's basically a deprecated feature and has been for
a long time. I've never seen it happen. Add another "except" clause and
use it to bitch at the user for throwing something that isn't an Exception
You won't find any other code that throws anything but an exception,
unless either you or your user wrote it.

 

[Kent Johnson]

I don't think I've quite got it.

The application I'm writing has some similarities to an interactive
shell. Like an interactive shell, it executes arbitrary code that it
receives from an input stream. When it gets an exception, it should
create an informative message, regardless of the type of exception. The
traceback routine does that, somehow, some way, but I've tried to read
that code and figure out how and I don't get it.

The best I have so far is,

class Exec_thread(BG_thread):
""" Execute a line of code in the global namespace. """
def _process(s):
""" Process one instruction """
try:
exec s.product in globals()
except (Exception), e:
handle_error( typename(e)+ ": " + str(e) )

Have you looked at the traceback module? If you want to print the same kind of trace you get from
Python, just use traceback.print_exc().

import traceback
try:
# whatever
except:
traceback.print_exc()

Kent