On 22May2016 08:19, Saidov <usai...@gmail.com> wrote:
Thank you all for the useful feedback. I am new to programming so bear
with me while I learn the rules...
I have run Cameron's code to print the values and have the traceback
results. please see below.
[...]
for row in records:
[...]
try:
expenses[ts.Date(row[0]).month] +=
decimal.Decimal(row[4])
except ValueError:
pass
[...]
I suggest that you print out the value of row[4] before the "try"
statement:
print("row[4] =", repr(row[4]))
[...]
+ decimal <module 'decimal' from 'C:\mypath\Anaconda3\\lib\\decimal.py'>
module
+ expenses {1: Decimal('0'), 2: Decimal('0'), 3: Decimal('0'), 4:
Decimal('0'), 5: Decimal('0'), 6: Decimal('0'), 7: Decimal('0'), 8:
Decimal('0'), 9: Decimal('0'), 10: Decimal('0'), 11: Decimal('0'), 12:
Decimal('0')} dict
row[0] '"1/1/2016"' str
row[4] '""' str
+ ts <module 'timestring' from
'C:\mypath\Anaconda3\\lib\\site-packages\\timestring\\__init__.py'>
module
ipython traceback:
row[4]= ' "" '
Traceback (most recent call last):
File "C:\mypath\visual studio
2015\Projects\Budget\Budget\Budget.py", line 28, in <module>
expenses[ts.Date(row[0]).month] += decimal.Decimal(row[4])
decimal.InvalidOperation: [<class 'decimal.ConversionSyntax'>]
I think the problem may be caused by an empty string value that is
passed to decimal.Decimal function. The csv file contains some empty
cells and I wanted the code to ignore them. That's why I had the
ValueError exception.
I have two observations here:
Your strings in row[4] are not empty. If that output is repr(row[4]) then
row[4] contains the text:
""
That is a two character string consisting of two quote characters.
Normally the csv.reader module will handle that for you, but I see that you
passed the paramater:
quoting=csv.QUOTE_NONE
to it when setting it up. It looks to me like your CSV file is a conventional
one with quotes around string values. By passing csv.QUOTE_NONE you prevent the
csv module from handling those for you and you get the "raw" column values. So
a column with an empty string is probably written as "" in the file.
Could you show is the first line or so from your CSV file? That should tell us
and you whether the file is "bare" comma separate values or the far more common
quoted format.
If it is the quoted format, just remove the "quoting=csv.QUOTE_NONE" parameter
altogether - the default for the csv module is quoted and it is _usually_ what
is wanted. Of course you need to know one way or the other, so examine the CSV
file itself.
The other observation is that you're trying to catch ValueError, when plainly
the Decimal module is raising decimal.InvalidOperation. So you should catch
that instead.
HOWEVER, just catching it and ignoring that row will _silently_ discard good
input if you program is incorrect. You should almost always emit an error
message or perform some other very specific action when you catch an exception.
Alan has suggested that you test specificly for an empty string.
I agree: you should act on exactly what is expected. By blindly catching
ValueError or decimal.InvalidOperation and not reporting the string that caused
it to happen you will silently ignore all kinds of unexpected input.
So I would advocate some code like this, similar to Alan's:
if not row[4]:
# empty column - we expect this and ignore it
pass
else:
try:
expenses[ts.Date(row[0]).month] += decimal.Decimal(row[4])
except decimal.InvalidOperation as e:
print("unexpected expenses value: %r" % (row[4],))
which will report the offending values, and presumably you expect either an
empty column or a _valid_ expense value.
Cheers,
Cameron Simpson <c...@zip.com.au>
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
https://mail.python.org/mailman/listinfo/tutor
