Python HTTP Exception Handling

Question

I'm running a program that downloads files from a web sit. I've introduced one exception handling urllib.error.HTTPError, but now I'm getting from time to time additional errors that I'm not sure how to capture: http.client.IncompleteRead. Do I just add the following to the code at the bottom?

except http.client.IncompleteRead:

How many exceptions do I have to add to make sure the program doesn't stop? And do I have to add them all in the same Except statement or in several Except statements.

try:
   # Open a file object for the webpage 
   f = urllib.request.urlopen(imageURL)
   # Open the local file where you will store the image
   imageF = open('{0}{1}{2}{3}'.format(dirImages, imageName, imageNumber, extension), 'wb')
   # Write the image to the local file
   imageF.write(f.read())
   # Clean up
   imageF.close()
   f.close()

except urllib.error.HTTPError: # The 'except' block executes if an HTTPError is thrown by the try block, then the program continues as usual.
   print ("Image fetch failed.")

Greg Hewgill · Accepted Answer · 2013-08-31 04:37:50Z

8

You can add individual except clauses if you want to handle each exception type separately, or you could put them all in one:

except (urllib.error.HTTPError, http.client.IncompleteRead):

You can also add a generic clause that will catch anything not handled previously:

except Exception:

For more informative messages, you can print the actual exception that happens:

except Exception as x:
    print(x)

answered Aug 31, 2013 at 4:37

Greg Hewgill

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2 Comments

gciriani Over a year ago

thanks. What will happen if the exception was caused by an inability to close the file or download the file, or other mishaps? Should I try to close the file as part of the code immediately following the except statement?

Greg Hewgill Over a year ago

@gciriani: You can use the finally clause to help ensure files are closed, or use the with statement which is a nicer way of doing that.

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