Newbie Question - Checkboxes

[Leanne]

I have been using Python for only a few months part-time and have
recently had my first encounter with retrieving user input from
checkboxes. I have a problem with the way Python reads the input
values from a set of checkboxes on a webpage.

The values assigned to the checkboxes are integers. I first of all
check for a key of CHK_CHILDREN to see if any checkboxes have been
checked. That works fine.

I then use a 'for x in CHK_CHILDREN' loop to get all the values from
the returned list. This works for most cases except one. If the user
only checks 1 checkbox, Python reads a scalar, not a list, and if this
scalar is a double digit integer (eg 11), then the loop goes through
each digit and retrieves these values, eg retrieves 1 and then
retrieves 1 again.

I have created a not so elegant work-around that names each checkbox a
different name and therefore I know a scalar is returned each time, but
was wondering if anyone knows what's going here.

Thanks

 

[Peter Otten]

I have been using Python for only a few months part-time and have
recently had my first encounter with retrieving user input from
checkboxes. I have a problem with the way Python reads the input
values from a set of checkboxes on a webpage.

The values assigned to the checkboxes are integers. I first of all
check for a key of CHK_CHILDREN to see if any checkboxes have been
checked. That works fine.

Checkboxes can be in Tkinter, wxPython, anything...
Try to read your post from the addressees' perspective before you hit
[Send].

I then use a 'for x in CHK_CHILDREN' loop to get all the values from
the returned list. This works for most cases except one. If the user
only checks 1 checkbox, Python reads a scalar, not a list, and if this
scalar is a double digit integer (eg 11), then the loop goes through
each digit and retrieves these values, eg retrieves 1 and then
retrieves 1 again.

I have created a not so elegant work-around that names each checkbox a
different name and therefore I know a scalar is returned each time, but
was wondering if anyone knows what's going here.

Are you perchance using the cgi module? If so, the following tip from the
documentation may be helpful:

http://docs.python.org/dev/lib/node558.html

"""
If the submitted form data contains more than one field with the same name,
the object retrieved by "form[key]" is not a FieldStorage or
MiniFieldStorage instance but a list of such instances. Similarly, in this
situation, "form.getvalue(key)" would return a list of strings. If you
expect this possibility (when your HTML form contains multiple fields with
the same name), use the getlist() function, which always returns a list of
values (so that you do not need to special-case the single item case). For
example, this code concatenates any number of username fields, separated by
commas:


value = form.getlist("username")
usernames = ",".join(value)
"""

Peter

 

[Leanne]

Thanks for your reply Peter. Sorry if my technical wording of the
problem is a bit lacking. I am still trying to put all parts of the
puzzle together in terms of the programming environment. The
checkboxes are in a PyMeld compatible HTML file. I'm using CherryPy
2.2.
Leanne

 

[John Machin]

I have been using Python for only a few months part-time and have
recently had my first encounter with retrieving user input from
checkboxes. I have a problem with the way Python reads the input
values from a set of checkboxes on a webpage.

The values assigned to the checkboxes are integers. I first of all
check for a key of CHK_CHILDREN to see if any checkboxes have been
checked. That works fine.

I then use a 'for x in CHK_CHILDREN' loop to get all the values from
the returned list. This works for most cases except one. If the user
only checks 1 checkbox, Python reads a scalar, not a list, and if this
scalar is a double digit integer (eg 11), then the loop goes through
each digit and retrieves these values, eg retrieves 1 and then
retrieves 1 again.

You evidently mean that the scalar you are getting is e.g. "11" and
your loop is returning "1" then "1" again. So there are two
possibilities: a string (either str or unicode) or a list (or some
other sequence).

I'd try this:

if isinstance(returned_value, basestring):
returned_value = [returned_value]
for item in returned_value:
do_something_with(item)

HTH,
John

 

[Leanne]

I'd try this:

if isinstance(returned_value, basestring):
returned_value = [returned_value]
for item in returned_value:
do_something_with(item)

HTH,
John

This sounds like a neat way of doing it, thanks!