beginner python cgi question

[Brandon Boles]

Hi folks,

I am trying to learn python, and have a form processing script giving me
this error:

Traceback (most recent call last):
File "inquiry", line 16, in ?
Address=fields["address"].value
File "/usr/local/python2.2/lib/python2.2/cgi.py", line 550, in __getitem__
raise KeyError, key
KeyError: address

This is the snippet of code the error is referring to:

....snip...
fields=cgi.FieldStorage()
if (fields.has_key("name") and fields.has_key("emailaddr")):
SenderName=fields["name"].value
Address=fields["address"].value
City=fields["city"].value
State=fields["state"].value
....snip...

I think what the problem is that if my form does not have one of the
fields (except 'name' and 'emailaddr') with data in it, I get this error.
What is the best way to fix this?

Please be kind, this is my first attempt at python. Thanks for the help!

Brandon

 

[Rene Pijlman]

Brandon Boles:

Address=fields["address"].value [...]
KeyError: address [...]
if (fields.has_key("name") and fields.has_key("emailaddr")):
SenderName=fields["name"].value
Address=fields["address"].value
City=fields["city"].value
State=fields["state"].value
...snip...

I think what the problem is that if my form does not have one of the
fields (except 'name' and 'emailaddr') with data in it, I get this error.
What is the best way to fix this?

One way is to use if has_key(), as you already discovered. The other way
is exception handling:

try:
Address = fields["address"].value
except KeyError, e:
Address = None # and/or report an error
else:
# do something with Address

 

[Jochen =?iso-8859-1?Q?Wersd=F6rfer?=]

+--[ Brandon Boles ]---[ (e-mail address removed) ]
| ...snip...
| fields=cgi.FieldStorage()
| if (fields.has_key("name") and fields.has_key("emailaddr")):
| SenderName=fields["name"].value
| Address=fields["address"].value
| City=fields["city"].value
| State=fields["state"].value
| ...snip...
|
| I think what the problem is that if my form does not have one of the
| fields (except 'name' and 'emailaddr') with data in it, I get this error.
| What is the best way to fix this?

Getting a default value, if "address" is not set:

Address = fields.get("address", "n/a")

jochen

 

[Jochen Wersdoerfer]

+--[ Brandon Boles ]---[ (e-mail address removed) ]
| ...snip...
| fields=cgi.FieldStorage()
| if (fields.has_key("name") and fields.has_key("emailaddr")):
| SenderName=fields["name"].value
| Address=fields["address"].value
| City=fields["city"].value
| State=fields["state"].value
| ...snip...
|
| I think what the problem is that if my form does not have one of the
| fields (except 'name' and 'emailaddr') with data in it, I get this error.
| What is the best way to fix this?

Getting a default value, if "address" is not set:

Address = fields.get("address", "n/a")

jochen

 

[Paolo G. Cantore]

Use 'fields=cgi.FieldStorage(keep-blank-values=1)' and you don't have to
worry about KeyErrors anymore.

Hope this helps.

Paolo

 

[Andrew Clover]

Address = fields.get("address", "n/a")

(You mean fields.getvalue, natch.)

If you don't want to have to deal with cgi returning a list sometimes, what
you really want is fields.getfirst('fieldname', 'default'), but this only
exists in Python 2.2 onwards.