How to determine in what function exception was raised. For example exist two functions: 'foo' and 'bar'. In 'foo' exception will raised randomly.
import random
def foo():
if random.randint(1, 10) % 2:
raise Exception
bar()
def bar():
raise Exception
try:
foo()
except Exception as e:
print "Exception raised in %s" % ???
import inspect
try:
foo()
except Exception as e:
print "Exception raised in %s" % inspect.trace()[-1][3]
I use the traceback module, like so:
import traceback
try:
1 / 0
except Exception:
print traceback.format_exc()
This gives the following output:
Traceback (most recent call last):
File "<ipython-input-3-6b05b5b621cb>", line 2, in <module>
1 / 0
ZeroDivisionError: integer division or modulo by zero
If the code runs from a file, the traceback will tell the line and character number of where the error occured :)
EDIT:
To accomodate the comment from Habibutsu: Yes, it's useful for printing, but when needed to get more info (for example function name) - not suitable
The doc-pages tell you how to extract the trace programmatically: http://docs.python.org/2/library/traceback.html
From the page linked above:
>>> import traceback
>>> def another_function():
... lumberstack()
...
>>> def lumberstack():
... traceback.print_stack()
... print repr(traceback.extract_stack())
... print repr(traceback.format_stack())
...
>>> another_function()
File "<doctest>", line 10, in <module>
another_function()
File "<doctest>", line 3, in another_function
lumberstack()
File "<doctest>", line 6, in lumberstack
traceback.print_stack()
[('<doctest>', 10, '<module>', 'another_function()'),
('<doctest>', 3, 'another_function', 'lumberstack()'),
('<doctest>', 7, 'lumberstack', 'print repr(traceback.extract_stack())')]
[' File "<doctest>", line 10, in <module>\n another_function()\n',
' File "<doctest>", line 3, in another_function\n lumberstack()\n',
' File "<doctest>", line 8, in lumberstack\n print repr(traceback.format_stack())\n']
The doc-string for traceback.extract_stack is the same as for traceback.extract_tb
traceback.extract_tb(traceback[, limit])
Return a list of up to limit “pre-processed” stack trace entries extracted from the traceback object traceback. It is useful for alternate formatting of stack traces. If limit is omitted or None, all entries are extracted. A “pre-processed” stack trace entry is a quadruple (filename, line number, function name, text) representing the information that is usually printed for a stack trace. The text is a string with leading and trailing whitespace stripped; if the source is not available it is None.
traceback is indeed suitable, and can be used to extract function names for example :)What is your goal? If you are worried about bar and foo throwing the same exception type and the caller not being able to differentiate between them, just derive a new exception class:
import random
class FooException(Exception):
"""An exception thrown only by foo."""
def foo():
if random.randint(1,10) % 2:
raise FooException
bar()
def bar():
raise Exception
try:
foo()
except FooException:
print "Exception raised in foo..."
except:
print "Exception raised in bar (probably)..."
