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Difference between bare except and specifying a specific exception

In this piece of code, I could write a simple except clause without writing Exception in front of it. I mean the last line could be like this :
except:
print('Hit an exception other than KeyError or NameError!')
What is the point of writing Exception in front of an except clause ?
try:
discounted_price(instrument, discount)
except KeyError:
print("There is a keyerror in your code")
except NameError:
print('There is a TypeError in your code')
except Exception:
print('an exception occured')
I tried writing an except clause without Exception keyword and it worked the same.
Thank you guys for your answers . I know the point of catching specific errors. If I want to ask more clearly , what is the difference between two clauses :
except Exception:
print('an exception occured')
except :
print('an exception occured')

The point of specifying the Exception is that ONLY that Exception will be caught, if you do not specify any Exception, then ALL Errors and Exceptions will be caught potentially masking bugs.
For example let's say that I want to read a file if it exists or otherwise print a message to the user, I can write:
try:
with ope("example.txt", "r") as f:
print(f.read())
except:
print("File not found")
But while this code runs fine without raising any exceptions, this code will never read the file, even if it exists!!!
This is because I wrote ope instead of open and the NameError was caught by my bare except, If I write the except in the correct way:
try:
with ope("example.txt", "r") as f:
print(f.read())
except FileNotFoundError:
print("File not found")
Now I can properly debug my code:
Traceback (most recent call last):
File "/home/riccardo/types.py", line 4, in <module>
with ope("example.txt", "r") as f:
NameError: name 'ope' is not defined

A bare expect
try:
...
except:
pass
or catching any exception whatsoever
try:
...
except Exception:
pass
are bad practice, because you can be hiding bug or be interfering with the normal procedure of the program.
You should only catch exception that you know how to handle, everything else you should let it propagate.
For some example:
Hide bug: it can hide some typo in your code as Caridorc example show making you think that you had a problem different than the real problem
Interfering with the normal procedure: you can make it an unexpectedly unkillable program or get in the way of the normal procedure of the program by discarding an exception that another part of the code was expecting.
like for example
while True:
try:
print("running")
except:
print("I'm immortal muahahaha")
this piece of code now you can't stop with you usual control-z (control-z throw and KeyboardInterrupt exception into your program) so you now need to close the whole interpreter/kill it with the task admin just to stop it, and if this was unintended you just introduced a new bug and depending on what you're doing it can be catastrophic.
To illustrate how catastrophic it can be, consider the following hypothetical case: imagine you make so benign function for a medical device and you put something like this
try:
...
except:
print("some error happens")
now it just so happens that while you piece of code was running a HeartAttack exception was raised and your catch it all and ignore piece of code will do, well, just that, and here is the twist this device was a pacemaker... well, congratulation you just killed the poor guy.
And that is why you should only catch the exception you know how to deal with, everything else you let it pass and hope that somebody along the line know how to deal with it, like in the example above, you and your piece of code don't know how to deal with a HeartAttack, but the pacemaker do and the pacemaker was the one that call your piece of code let it deal with it...
for a no so extreme example consider this simple code
def get_number_from_user():
while True:
try:
return int(input("write a number: "))
except:
print("not a valid number try again")
if your user was done with your program and this happens to be the thing running he/she might want to kill it with a control-z as you usually do with any program, but it will find that it doesn't work, the correct way here is to catch the error we know how to deal with in this case, namely ValueError, everything else isn't this function business
def get_number_from_user():
while True:
try:
return int(input("write a number: "))
except ValueError:
print("not a valid number try again")
You also ask about the difference between
try:
...
except:
pass
and this
try:
...
except Exception:
pass
the difference is that a bare except can catch any and all kind of exception, that in python is anything that is or inherit from BaseException that sit at the top of the exception hierarchy, while except Exception will catch only Exception itself or anything that inherit from it (the same apply for any particular exception you put there), this small distinction allow to make some exceptions more special than other, like the aforementioned KeyboardInterrupt that inherit from BaseException instead of Exception, and that is used to signal that the user wants to terminate this program, so you should do so and this distinction is made basically so new programmers don't shoot themselves in the foot when using except Exception

Just to add to the answer provided by #Caridorc, by specifying each error separately, you can run specific error handling code pertaining to that error when the exception arises. If for example the file does not exist, you can print message to that effect. If however, it fails to print because you mistyped g instead of f, you can print a message to say that the variable is not recognised ( separate code for separate error captures). For exmple:
g = 100 # Unrelated variable declared previously
try:
with open("example.txt", "r") as f:
x=print(f.read())
except FileNotFoundError:
print("File not found")
except AttributeError:
print("Reading wrong variable")
except Exception as e:
print("Unknown Error", e)
Note also the last exception except Exception as e:. This is the same as just except: but allows you to handle all other errors that do not fit onto previous captures and retrieve e - the error message that is generated by compiler. There is effectively no difference between except: and except Exception: in terms of execution

Consider the code:
a = 5
b = 0
x = a / b
Executing this will alert you to the fact that you have attempted to divide a float by zero but it will crash your code.
Now consider:
a = 5
b = 0
try:
x = a / b
except: # or 'except Exception:'
print("An exception was raised")
This will raise an exception that is handled by printing a message that an error occurred. You code will not crash but you do not know how to properly handle the code because you do not know what the exception was, just that one occurred.
Now consider:
a = 5
b = 0
try:
x = a / b
except Exception as e:
print("An exception was raised, generating error", e)
Now your code does not crash. Is handled and you know what the error was.

The purpose of writing "Exception" in front of an except clause is to catch all possible exceptions that can occur in the code. By specifying "Exception", you are telling the interpreter to handle any type of exception that might be raised. The more specific the exception specified in the except clause, the more targeted the handling of the exception can be. For example, if you only want to handle "KeyError" exceptions, you can specify that explicitly in the except clause, as in the first example.

Create exception routine if module not found Python

I have a simple Python programm. This programm contains two functions, that can be called by using programm.function_1() from a second programm. If a user types package.function_01() the attribute error 'module not found' comes up. I want to except that error and call the function help().
Where do I have to insert my try - except routine to handle the attribute error?
Thanks in advance!

Surround the code that can break with a try ... except block. You may call your Exception handler under the except SomeException: clause
Take a look into Python exception docs enter link description here

why do we use 'pass' in error handling of python?

It is conventional to use pass statement in python like the following piece of code.
try:
os.makedirs(dir)
except OSError:
pass
So, 'pass' bascially does not do anything here. In this case, why would we still put a few codes like this in the program? I am confused. Many thanks for your time and attention.

It's for the parser. If you wrote this:
try:
# Code
except Error:
And then put nothing in the except spot, the parser would signal an error because it would incorrectly identify the next indentation level. Imagine this code:
def f(x):
try:
# Something
except Error:
def g(x):
# More code
The parser was expecting a statement with a greater indentation than the except statement but got a new top-level definition. pass is simply filler to satisfy the parser.

This is in case you want the code to continue right after the lines in the try block. If you won't catch it - it either skips execution until it is caught elsewhere - or fails the program altogether.
Suppose you're creating a program that attempts to print to a printer, but also prints to the standard output - you may not want it to file if the printer is not available:
try:
print_to_printer('hello world')
except NoPrinterError:
pass # no printer - that's fine
print("hello world")
If you would not use a try-catch an error would stop execution until the exception is caught (or would fail the program) and nothing would be printed to standard output.

The pass is used to tell the program what to do when it catches an error. In this particular case you're pretty much ignoring it. So you're running your script and if you experience an error keep going without worrying as to why and how.
That particular case is when you are definite on what is expected. There are other cases where you can break and end the program, or even assign the error to a variable so you can debug your program by using except Error as e.
try:
os.makedirs(dir)
except OSError:
break
or:
try:
os.makedirs(dir)
except OSError as e:
print(str(e))

try:
# Do something
except:
# again some code
# few more code
There are two uses of pass. First, and most important use :- if exception arises for the code under try, the execution will jump to except block. And if you have nothing inside the except block, it will throw IndentationError at the first place. So, to avoid this error, even if you have nothing to do when exception arises, you need to put pass inside except block.
The second use, if you have some more code pieces after the try-except block (e.g. again some code and few more code), and you don't put pass inside except, then that code piece will not be executed (actually the whole code will not be executed since compiler will throw IndentationError). So, in order to gracefully handle the scenario and tell the interpreter to execute the lines after except block, we need to put pass inside the except block, even though we don't want to do anything in case of exception.
So, here pass as indicated from name, handles the except block and then transfers the execution to the next lines below the except block.

Python reraise/recatch exception

I would like to know if it is possible in python to raise an exception in one except block and catch it in a later except block. I believe some other languages do this by default.
Here is what it would look like"
try:
something
except SpecificError as ex:
if str(ex) = "some error I am expecting"
print "close softly"
else:
raise
except Exception as ex:
print "did not close softly"
raise
I want the raise in the else clause to trigger the final except statement.
In actuality I am not printing anything but logging it and I want to log more in the case that it is the error message that I am not expecting. However this additional logging will be included in the final except.
I believe one solution would be to make a function if it does not close softly which is called in the final except and in the else clause. But that seems unnecessary.

What about writing 2 try...except blocks like this:
try:
try:
something
except SpecificError as ex:
if str(ex) == "some error I am expecting"
print "close softly"
else:
raise ex
except Exception as ex:
print "did not close softly"
raise ex

Only a single except clause in a try block is invoked. If you want the exception to be caught higher up then you will need to use nested try blocks.

As per python tutorial there is one and only one catched exception per one try statement.
You can find pretty simple example in tutorial that will also show you how to correctly use error formatting.
Anyway why do you really need second one? Could you provide more details on this?

You can do this using the six package.
Six provides simple utilities for wrapping over differences between Python 2 and Python 3.
Specifically, see six.reraise:
Reraise an exception, possibly with a different traceback. In the simple case, reraise(*sys.exc_info()) with an active exception (in an except block) reraises the current exception with the last traceback. A different traceback can be specified with the exc_traceback parameter. Note that since the exception reraising is done within the reraise() function, Python will attach the call frame of reraise() to whatever traceback is raised.

How to see the error and still keep the program on in the Python shell?

I know try/except can handle errors in my program.
But, is there a way of making the error be displayed in the program execution, be ignored and let the execution go on?

In VBScript and other VB-derived languages, you can get this sort of behavior with "ON ERROR GOTO NEXT".
No such behavior exists in Python. Even if you wrap each top-level statement like:
try:
do_something()
except Exception as e:
print e
try:
do_something_else()
except Exception as e:
print e
you'd still have the result that statements within do_something are skipped at the point the exception is thrown.
Though perhaps if you have a particular use-case in mind, there may be other acceptable answers. For instance, in a top-level loop:
while True:
cmd = get_command()
if cmd == 'quit': break
try:
run_command(cmd)
except Exception as e:
print "Error running " + cmd + ":"
print e

import traceback
try:
# do whatever you want
except Exception:
traceback.print_exc()
Of course you should be more specific in a real scenario, i.e. you shouldn't catch and ignore all Exception instances, only the ones you are interested in and you know that they are safe to ignore.
Also note that if an exception happens somewhere within the try..except block, the execution will continue after the try..except block, not at the next statement. This is probably the closest to what you want to achieve.