Explain the control flow in try, except and finally blocks ?

Question

try:
print(1)
print(10 / 0)
except ZeroDivisionError:
print(unknown_var)
finally:
print("This is executed last")

in the above code when exception occured in the except block, the control went to finally block and then returns back to the except block to print the exception

Answer 1

Saswata Das Flow is simple

1 - try
2 - except
3 - finally

If finally will be execute before the except then output will be different. Did you get different output? I didn't get.

Answer 2

try: if error occurs goto except else goto finally

except: if error occurs it's propagated to the enclosing scope* and handled normally(after finally) and goto finally no matter what happened.

finally: always runs. If error occurs it's handled as usual.

*In your code the "unknown_var" error is not handled but consider:
try:
try:
print(1)
print(10/0)
except ZeroDivisionError:
print(unknown_var)
finally:
print("This is executed last")
except:
pass #do nothing

Answer 3

Try is used to test the code.
If any error occurs, the error mentioned in except block runs..
Note:-
If any error is not mentioned, it takes all the errors.
If the code in try block gives an error, the block in finally statements runs no matter what error occurs....
Then, it will give error of try statement, whatever error occurs is mentioned in except block..
That's why it first went to finally and gave the error of code mentioned in except block...
Hope it is clear now 🙂

Answer 4

The code will first print 1, then it will check the next statement, 'print 10/0'. Since this statement will create an error (ZeroDivisionError).

This error will get excepted by the statement 'except Zerodivisionerror'. It will then run the code in that block.

As there is another error (undefined variable) under the except statement, it will not run that block.

The 'finally' keyword will run the block of code no matter what, therefore, it will execute the statement 'print( 'this is executed last' )