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Given error when trying to iterate through an exception

I am making a Reddit bot using PRAW and the code gives me the error that the exception is not iterable. Here is a simplification of my code:
try:
#something with praw that isn't relevant
except Exception as e: #this except error catches the APIexception, APIexpections in PRAW are a wide field of exceptions that dont't always have the same solution, so I scan the text for the error I'm looking for.
print(e)
if "keyword thats in the error" in e:
#fix the problem with the specific error
else:
print("Unkown APIExpection error")
This works fine for me, but when I run this code:
try:
#something
except Exception as e:
for character in e:
print(character)
#I also tried this
try:
#something
except Exception as e:
for character in str(e):
print(character)
#None of the above work but this is my actual code and what I need to do, anything that gets the above to work should work here too, I'm just letting you know this so that I don't get any other errors I have to ask another question for.
try:
#something
except Exception as e:
characterNum = 0
for character in e:
characterNum += 1
print(str(characterNum) + ": " + character)
It gives me a "TypeError: 'RedditAPIException' is not iterable", RedditAPIException can be ignore though as that's just the error I'm catching.

Convert the exception to string and then check in the if statement.
Change to => if "keyword thats in the error" in str(e):

Handling PyMySql exceptions - Best Practices

My question regards exception best practices.
I'll present my question on a specific case with PyMySQL but it regards errors handling in general.
I am using PyMySQL and out of the many possible exceptions, there is one I want to deal with in a specific manner. "Duplicate" exception.
pymysql maps mysql errors to python errors according to the following table:
_map_error(ProgrammingError, ER.DB_CREATE_EXISTS, ER.SYNTAX_ERROR,
ER.PARSE_ERROR, ER.NO_SUCH_TABLE, ER.WRONG_DB_NAME,
ER.WRONG_TABLE_NAME, ER.FIELD_SPECIFIED_TWICE,
ER.INVALID_GROUP_FUNC_USE, ER.UNSUPPORTED_EXTENSION,
ER.TABLE_MUST_HAVE_COLUMNS, ER.CANT_DO_THIS_DURING_AN_TRANSACTION)
_map_error(DataError, ER.WARN_DATA_TRUNCATED, ER.WARN_NULL_TO_NOTNULL,
ER.WARN_DATA_OUT_OF_RANGE, ER.NO_DEFAULT, ER.PRIMARY_CANT_HAVE_NULL,
ER.DATA_TOO_LONG, ER.DATETIME_FUNCTION_OVERFLOW)
_map_error(IntegrityError, ER.DUP_ENTRY, ER.NO_REFERENCED_ROW,
ER.NO_REFERENCED_ROW_2, ER.ROW_IS_REFERENCED, ER.ROW_IS_REFERENCED_2,
ER.CANNOT_ADD_FOREIGN, ER.BAD_NULL_ERROR)
_map_error(NotSupportedError, ER.WARNING_NOT_COMPLETE_ROLLBACK,
ER.NOT_SUPPORTED_YET, ER.FEATURE_DISABLED, ER.UNKNOWN_STORAGE_ENGINE)
_map_error(OperationalError, ER.DBACCESS_DENIED_ERROR, ER.ACCESS_DENIED_ERROR,
ER.CON_COUNT_ERROR, ER.TABLEACCESS_DENIED_ERROR,
ER.COLUMNACCESS_DENIED_ERROR)
I want to specifically catch ER.DUP_ENTRY but I only know how to catch IntegrityError and that leads to redundant cases within my exception catch.
cur.execute(query, values)
except IntegrityError as e:
if e and e[0] == PYMYSQL_DUPLICATE_ERROR:
handel_duplicate_pymysql_exception(e, func_a)
else:
handel_unknown_pymysql_exception(e, func_b)
except Exception as e:
handel_unknown_pymysql_exception(e, func_b)
Is there a way to simply catch only ER.DUP_ENTRY some how?
looking for something like:
except IntegrityError.DUP_ENTRY as e:
handel_duplicate_pymysql_exception(e, func_a)
Thanks in advance for your guidance,

there is very generic way to use pymysql error handling. I am using this for sqlutil module. This way you can catch all your errors raised by pymysql without thinking about its type.
try:
connection.close()
print("connection closed successfully")
except pymysql.Error as e:
print("could not close connection error pymysql %d: %s" %(e.args[0], e.args[1]))

You cannot specify an expect clause based on an exception instance attribute obviously, and not even on an exception class attribute FWIW - it only works on exception type.
A solution to your problem is to have two nested try/except blocks, the inner one handling duplicate entries and re-raising other IntegrityErrors, the outer one being the generic case:
try:
try:
cur.execute(query, values)
except IntegrityError as e:
if e.args[0] == PYMYSQL_DUPLICATE_ERROR:
handle_duplicate_pymysql_exception(e, func_a)
else:
raise
except Exception as e:
handle_unknown_pymysql_exception(e, func_b)
Whether this is better than having a duplicate call to handle_unknown_pymysql_exception is up to you...

When PyMongo throws a DuplicateKeyError How can I tell what field caused the conflict? [duplicate]

In pymongo, when a DuplicateKeyError caught, what's the proper way to find out the duplicate value behind the the exception?
Currently I do this
try:
db.coll.insert({key: ['some_value', 'some_value_1']})
except pymongo.errors.DuplicateKeyError, e:
dups = re.findall(r'\{\ +:\ +"(.*)"\ +\}$', e.message)
if len(dups) == 1:
print dups[0]
It seems to work, but is there any easier way, like
try:
db.coll.insert({key: ['some_value', 'some_value_1']})
except pymongo.errors.DuplicateKeyError, e:
print e.dup_val
EDIT
It's a concurrent app, so check duplicates before insert might fail.
The field is an array, so it's hard to find out which one is the duplicate value.

In dev version of pymongo (2.7) you can check with error_document property:
try:
db.coll.insert({name: 'some_value'})
except pymongo.errors.DuplicateKeyError, e:
print e.error_document
As far as I know, in 2.6 and earlier versions, all info except error msg and code is discarded.

Python trying fails

I am trying in Python.
try:
newbutton['roundcornerradius'] = buttondata['roundcornerradius']
buttons.append(newbutton)
buttons is a list. roundcornerradius is optional in buttondata.
Alas this gives
buttons.append(newbutton)
^ SyntaxError: invalid syntax
I just want to ignore the cases where roundcornerradius does not exist. I don't need any error reported.

why arent you using the except keyword
try:
newbutton['roundcornerradius'] = buttondata['roundcornerradius']
buttons.append(newbutton)
except:
pass
this will try the first part and if an error is thrown it will do the except part
you can also add the disered error you want to except a certain error like this
except AttributeError:
you can also get the excepted error by doing this:
except Exception,e: print str(e)

You should catch a try with exception:
try:
code may through exception
except (DesiredException):
in case of exception
Also you can use else with try if you need to populate new buttons only when try succeeds:
try:
newbutton['roundcornerradius'] = buttondata['roundcornerradius']
except KeyError:
pass
else:
buttons.append(newbutton)
single except: with no exception class defined will catch every exception raised which may not be desired in some cases.
Most probably you will get KeyError on your code but I am not sure.
See here for builtin exceptions:
http://docs.python.org/2/library/exceptions.html

You must close block with except or finally if using try.
try:
newbutton['roundcornerradius'] = buttondata['roundcornerradius']
except KeyError:
pass#omit raise if key 'roundcornerradius' does not exists
buttons.append(newbutton)
If you know default value for 'roundcornerradius' - you dont need no try ... except
newbutton['roundcornerradius'] = buttondata.get('roundcornerradius', DEFAULT_RADIUS)
buttons.append(newbutton)

How to identify what function call raise an exception in Python?

i need to identify who raise an exception to handle better str error, is there a way ?
look at my example:
try:
os.mkdir('/valid_created_dir')
os.listdir('/invalid_path')
except OSError, msg:
# here i want i way to identify who raise the exception
if is_mkdir_who_raise_an_exception:
do some things
if is_listdir_who_raise_an_exception:
do other things ..
how i can handle this, in python ?

If you have completely separate tasks to execute depending on which function failed, as your code seems to show, then separate try/exec blocks, as the existing answers suggest, may be better (though you may probably need to skip the second part if the first one has failed).
If you have many things that you need to do in either case, and only a little amount of work that depends on which function failed, then separating might create a lot of duplication and repetition so the form you suggested may well be preferable. The traceback module in Python's standard library can help in this case:
import os, sys, traceback
try:
os.mkdir('/valid_created_dir')
os.listdir('/invalid_path')
except OSError, msg:
tb = sys.exc_info()[-1]
stk = traceback.extract_tb(tb, 1)
fname = stk[0][2]
print 'The failing function was', fname
Of course instead of the print you'll use if checks to decide exactly what processing to do.

Wrap in "try/catch" each function individually.
try:
os.mkdir('/valid_created_dir')
except Exception,e:
## doing something,
## quite probably skipping the next try statement
try:
os.listdir('/invalid_path')
except OSError, msg:
## do something
This will help readability/comprehension anyways.

How about the simple solution:
try:
os.mkdir('/valid_created_dir')
except OSError, msg:
# it_is_mkdir_whow_raise_ane_xception:
do some things
try:
os.listdir('/invalid_path')
except OSError, msg:
# it_is_listdir_who_raise_ane_xception:
do other things ..

Here's the clean approach: attach additional information to the exception where it happens, and then use it in a unified place:
import os, sys
def func():
try:
os.mkdir('/dir')
except OSError, e:
if e.errno != os.errno.EEXIST:
e.action = "creating directory"
raise
try:
os.listdir('/invalid_path')
except OSError, e:
e.action = "reading directory"
raise
try:
func()
except Exception, e:
if getattr(e, "action", None):
text = "Error %s: %s" % (e.action, e)
else:
text = str(e)
sys.exit(text)
In practice, you'd want to create wrappers for functions like mkdir and listdir if you want to do this, rather than scattering small try/except blocks all over your code.
Normally, I don't find this level of detail in error messages so important (the Python message is usually plenty), but this is a clean way to do it.