[reportlab-users] upc-a barcodes

[Steve Romanow]

  On 9/8/2010 10:43 AM, Peter wrote:

> On Wed, Sep 8, 2010 at 2:37 PM, Steve Romanow<slestak989 at gmail.com>  wrote:

>>> It has been a while since I worked on this, but aren't 12 digit UPC-12

>>> barcodes the same thing as a 13 digit EAN barcode with a leading

>>> zero added?

>>>

>>> In a sense, you *have* to look at the length to tell them apart ;)

>> I think my difficulty with this stems from storage of UPC values with the

>> check digit already computed.  Even if I took off the last char, the barcode

>> was still shifted one position when using ean.py.  I have moved on to

>> another task, but will revisit this in the future.

> Again, this is from memory, but isn't the check digit the trailing (right

> most) digit? On the other hand, the "extra" leading zero present in

> EAN13 barcodes is the left-most digit.

>

> I don't recall the details, but computing the check digit on demand

> is pretty easy.

>

> If you are storing 11 digit UPC numbers without the check digit, you

> would have to compute and append the missing checkdigit to get a

> full 12 digit UPC number, and add the leading zero if you wanted to

> turn this into a full 13 digit EAN number. (Or do the reverse if that

> is what you meant).

>

> Peter

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IIRC, the ean.py routine does the check digit calculation for you, even 
if you already have it on there.