Python Programming for Raspberry Pi, Sams Teach Yourself in 24 Hours

Enter. At the Please enter file to open: prompt, type testfile and

press Enter. This should complete successfully, and you should receive the message

File testfile opened successfully!, as shown below.

Click here to view code image

pi@raspberrypi ~ $ python3 py3prog/script1704.py

Please enter file to open: testfile

File testfile opened successfully!

pi@raspberrypi ~ $

8. Now test your script again by typing python3 py3prog/script1704.py
   and pressing Enter. At the Please enter file to open: prompt, type
   nofile and press Enter. This should cause the script to abruptly halt (assuming that
   you do not have a file called nofile), and you should get an ugly traceback
   message similar to what is shown below:

Click here to view code image

pi@raspberrypi ~ $ python3 py3prog/script1704.py

Plvease enter file to open: nofile

Traceback (most recent call last):

File "py3prog/script1704.py", line 46, in <module>

main()

File "py3prog/script1704.py", line 42, in main

open_it (file_name)

File "py3prog/script1704.py", line 32, in open_it

my_file=open(file_name,'r')

IOError: [Errno 2] No such file or directory: 'nofile'

pi@raspberrypi ~ $

Obviously, you need to do more to get script1704.py into shape.

9. Open script1704.py in a script editor again. Modify the open_it function so
   that it looks as shown below:

Click here to view code image

def open_it (file_name): #Open file name

#

try:

my_file=open(file_name,'r')

print ("File", file_name, "opened successfully!")

my_file.close()

#

except Exception as open_error:

print ("An error exception has been raised.")

print ("The error message is:")

print (open_error)

print ()

return ()

#

10. Notice that the except statement uses Exception as the name of the exception.
    This is the overall base group for exceptions. In order to catch the exception using