Error checking in python

Question

After struggling with data download with ill tempered CSV fields. How could use try/Except format.

LL = [(XXX,YYY,ZZZ),] or [[XXX,YYY,ZZZ],]

if above, how do i do below?

try: 
   IF XXX or YYY or ZZZ or AAA == 'N/A',
   (dont process data...skip to except and pass)
except:
   pass

staeted here: Remove/Replace Error from Tuple in python

Martin Stone · Accepted Answer · 2011-03-04 18:41:12Z

1

Note that it's generally a bad idea to do a plain except:, as it will swallow exceptions that you need to know about.

LL = [("bad line",456,"N/A"),["good line", 123, 456],]

for line in LL:
    try: 
        if "N/A" in line:
            raise ValueError

        print line[0]

    except ValueError:
        print "skipped"

edited Mar 4, 2011 at 18:41

answered Mar 4, 2011 at 18:33

Martin Stone

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4 Comments

John Machin Over a year ago

-1 Raising an exception only to trap it yourself in the same try block is ludicrous. Use if/else!

Martin Stone Over a year ago

@John Machin, OP asked for an example using exceptions. Admittedly, it's not what I would have done if the actual code is really this trivial.

John Machin Over a year ago

It's not what you should have done in non-trivial code either.

Vamana Over a year ago

There are cases where raising and catching your own exception is a good technique. For example, if you have nested loops, or if there are other exceptions that might be raised. It can make the code simpler and more readable.

Xavier Combelle · Accepted Answer · 2011-03-04 18:44:34Z

1

UPDATED

I suppose like that

try: 
   if "N/A" in [XXX,YYY,ZZZ,AAA]
       raise Exception()
except:
   pass

edited Mar 4, 2011 at 18:44

answered Mar 4, 2011 at 18:28

Xavier Combelle

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1 Comment

Martin Stone Over a year ago

Assuming the original question was pseudocode and intended to check all fields against "N/A", this won't work. E.g. if XXX is "truthy", you'll throw the exception. (Same with YYY and ZZZ). These three aren't checked against "N/A".

nesv · Accepted Answer · 2011-03-06 03:32:33Z

1

for data in LL:
   try:
      if "N/A" in data:
         continue
      else:
         x, y, z = data
         # Process data...
   except Exception:
      continue

edited Mar 6, 2011 at 3:32

answered Mar 4, 2011 at 18:28

nesv

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1 Comment

g.d.d.c Over a year ago

I like this, but would change the conditional to if 'N/A' in (x, y, z) - it's cleaner and easier to read.

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