#As file is not present. It will raise the exception
f=open('yo.txt')

---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
<ipython-input-5-7f472f9bb708> in <module>
      1 #As file is not present. It will raise the exception
----> 2 f=open('yo.txt')

FileNotFoundError: [Errno 2] No such file or directory: 'yo.txt'

#Exception Handled using try and except block, in this code we gave Exception in except block. which will handled any type of exception and print file doesn't exist. 
#But it's always better to give the exception name and print message accordingly.
try:
    f=open("yo.txt")
except Exception:
    print("Sorry the file doesn't exist")

Sorry the file doesn't exist

#To show you why not except every exception, i will create a file yo.txt and not set 000 permission of file.
f=open('yo.txt')
#this time it gave as PermissionError

---------------------------------------------------------------------------
PermissionError                           Traceback (most recent call last)
<ipython-input-7-360478936479> in <module>
      1 #To show you why not except every exception, i will create a file yo.txt and not set 000 permission of file.
----> 2 f=open('yo.txt')
      3 #this time it gave as PermissionError

PermissionError: [Errno 13] Permission denied: 'yo.txt'

#Now when we run above try and except block
try:
    f=open("yo.txt")
except Exception:
    print("Sorry the file doesn't exist")
#It will print exact same error for every exception
#Goal of try and except is not to work around all the exception which we may run to, its to handle the exception and print accordingly.

Sorry the file doesn't exist

#when file is not present, exception FileNotFoundError exception handled
try:
    f=open("yo.txt")
except FileNotFoundError:
    print("Sorry the file doesn't exist")

Sorry the file doesn't exist

#when permission exception is raise in above code, which is a good thing
try:
    f=open("yo.txt")
except FileNotFoundError:
    print("Sorry the file doesn't exist")

---------------------------------------------------------------------------
PermissionError                           Traceback (most recent call last)
<ipython-input-12-00ca3cb9878c> in <module>
      1 #when permission exception is raise in above code
      2 try:
----> 3     f=open("yo.txt")
      4 except FileNotFoundError:
      5     print("Sorry the file doesn't exist")

PermissionError: [Errno 13] Permission denied: 'yo.txt'

#you can handle as many exception as you want and print message accordingly. but always except general exception at last.
#you can also print exact exception instead of custom messages
try:
    f=open("yo.txt")
except FileNotFoundError:
    print("Sorry the file doesn't exist")
except PermissionError as e:
    print(e)
except Exception:
    print("Sorry something went wrong")

[Errno 13] Permission denied: 'yo.txt'

#if you dont want custom message for any exception. you can always do this.
try:
    f=open("yo.txt")
except Exception as e:
    print(e)

[Errno 2] No such file or directory: 'yo.txt'

#else will execute the code if try block doesnt raise the exception
try:
    f=open("yo.txt")
except Exception as e:
    print(e)
else:
    print(f.read())
    f.close()

test file Contents!

#Regardless of what happen in try and catch block, finally block always get executed.
try:
    f=open("yo.txt")
except Exception as e:
    print(e)
else:
    print(f.read())
    f.close()
finally:
    print("This blocks contain something thats need to be done, no matter what, like closing the DB")

test file Contents!

This blocks contain something thats need to be done, no matter what, like closing the DB

#Above code with exception
try:
    f=open("yo.txt")
except Exception as e:
    print(e)
else:
    print(f.read())
    f.close()
finally:
    print("This blocks contain something thats need to be done, no matter what, like closing the DB")

[Errno 2] No such file or directory: 'yo.txt'
This blocks contain something thats need to be done, no matter what, like closing the DB

#TO manually raise exception
try:
    f=open("corrupte_file.txt")
    if f.name=='corrupte_file.txt':
        raise Exception
except FileNotFoundError:
    print("Sorry the file doesn't exist")
except PermissionError as e:
    print(e)
except Exception as e:
    print("File Corrupted!!!!!")

File Corrupted!!!!!