Creating a pythonic snippet to read and clean .csv files

Question

I am trying to import a .csv file, clean the contents, and make sure all the errors are eliminated.

• IO error
• file format error
• data error

I am using the snippet below. Could someone help me clean it and make it more pythonic?

try:
 fl = request.FILES['csv']
except:
 return HttpResponse("Some IO Error")
try: 
 reader = csv.reader(fl)
except:
 return HttpResponse("File Not Supported")
reader.next() # this makes sure the heading is 
cleaned_csv_content = list()
for row in reader:
 err = 0
 fname, lname, e_mail = row
 try:
 validate_email(email)
 except:
 pass
 err = 1
 if not err:
 cleaned_csv_content.append(fname, lname, e_mail)

Answer 1

Firstly, you should raise not return your errors.

Secondly, try: with a bare except: is bad practice (e.g. http://blog.codekills.net/2011/09/29/the-evils-of--except--/); what do you expect could go wrong with each step? Test for specific errors and deal with them appropriately. It is this which has hidden the NameError I mention at the end.

Thirdly, your use of the flag err seems a bit odd; much more Pythonic to use an actual boolean err = False or, better, else::

try:
 validate_email(e_mail) # see comment below
except: # but only the errors you expect - see above 
 pass
else:
 cleaned_csv_content.append((fname, lname, e_mail)) # note additional parentheses

or, even better, refactor validate_email to return True for a valid email and False otherwise, rather than raising errors:

if validate_email(e_mail):
 cleaned_csv_content.append((fname, lname, e_mail))

Finally, note that "email" != "e_mail".

• Ram Kumar: how about the for loops, can that be made more idiomatic?
• jonrsharpe: No; for row in reader: is fine and the tuple unpacking of each row is very Pythonic
• Ram Kumar: I am getting this error - Error: 'line contains NULL byte' for row in reader Any corrections?
• jonrsharpe: Not to the code, as such; you will need to look at your input data and what is ending up in reader, or use another try and handle that specific error appropriately (e.g. pass on that line).
• Ram Kumar: thanks done, another doubt. I am getting output of - for row in readline: print row as follows ['First Name\tLast Name\tEmail Address'] ['ASdf \tasdf\[email protected]'] The delimiter here is \t, any idea how to fix it?