nephish a écrit :
> Hey there,
> i am trying to write an online application using the cgi module.
> what i want to do is have an html form display a drop-down list and
> have the values of that list be the lines of text written in a file.
Simplest, Q&D solution :
1/ open the file for reading
2/ print out the beginning of the html tags for the dropdown (hint: in
html, it's <input type="select">)
3/ for each line in the file, print out the html tags and the line
4/ print out the end of the html
5/ close the file
which gives (first try, Q&D, naive implementation, no error handling, etc:
f = open("myfile.txt")
print "<input type='select' name='my-drop-down-list'>"
for line in f:
print "<option>%s</option>" % line.strip()
print "</input>"
f.close()
Now there may be some conditions we want to handle: file doesnt exist or
is not readable, file is empty, a line is empty, etc. A second try could
be like:
try:
f = open("myfile.txt")
except IOError, e:
# TODO : handle error. in the meantime:
print "could not open myfile.txt for reading : %s" % e
sys.exit(1)
else:
print "<input type='select' name='my-drop-down-list'>"
for line in f:
if line.strip():
print "<option>%s</option>" % line.strip()
print "</input>"
f.close()
Well... This does not handle all potential problems, and we begin to
have useless repetitions (here the 'line.strip()' expression). We need
to stop and think a little bit.
This snippet tries to do too many things at once: reading a file line by
line, and printing the html for a select. Since we won't use selects for
huge lists (for obvious usability reasons), we can assume that working
with an in-memory list will be ok. So we could split this in two parts:
one that read the file and returns a cleaned-up, ready to use list, and
one that output the needed html:
# first part
try:
f = open("myfile.txt")
except IOError, e:
# TODO : handle error. in the meantime:
print "could not open myfile.txt for reading : %s" % e
sys.exit(1)
else:
options = filter(None, [line.strip() for line in f])
f.close()
# second part:
if options:
print "<input type='select' name='my-drop-down-list'>"
for line in options:
print "<option>%s</option>" % line
print "</input>"
else:
# Err ? what should we do here ?
print "<i>no selectable option here</i>"
Hmm... Better, but still not ok. We can already guess that both parts
can be useful indepently of each other, in in other contexts. So why not
making this a little be generic ?
def listFrom(openedFile):
return filter(None, [line.strip() for line in openedFile])
def printSelect(name, options):
print "<input type='select' name='%s'>" % name
for line in options:
print "<option>%s</option>" % line
print "</input>"
def printSelectFromFile(name, path):
try:
f = open(path)
except IOError, e:
# TODO : handle error. in the meantime:
print "could not open %s for reading : %s" % (path, e)
sys.exit(1)
else:
options = listFrom(f)
f.close()
if options:
printDropdownList(name, options)
else:
print "<i>no selectable option here</i>"
Well, this could of course be much more improved, but this will depend
on stuffs specific to your application, so I'll leave it up to you...
> this would be updated almost every time the site is visited.
Err... Better take care of concurrent access...
> i have been sucessful in writing text to a file from an html form. but
> i need to access this so it can be selected.
> is there a way to do this? i have found limited info on how to really
> use the cgi module.
AFAICT, there's nothing related to the cgi module in your problem.
HTH
Bruno
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