So I've been working with
Django lately, and I continue to be pleased with the preeminent saneness with which it handles the interaction between HTML and Python. Here is the latest example.
Suppose you have an HTML form that your Django backend will be processing. Give each
input or
select element in your form a
name attribute, and whatever function you POST the form back to will receive a
request.POST dictionary keyed by the
name. For instance, if you have a form like this:
<form id="shopping">
<p>
<select name="fruit">
<option value="apples">apples</option>
<option value="bananas">bananas</option>
<option value="cherries">cherries</option>
</select>
</p>
<p>
<select name="meat">
<option value="buffalo">buffalo</option>
<option value="moose">moose</option>
<option value="quail">quail</option>
</select>
</p>
<input type="submit" value="Submit" />
</form>
Then your receiving function will get a
request.POST consisting of a dictionary with the keys
fruit and
meat, and the value for each will be a list containing the values that were selected. And, yes, if you give those
selects the
multiple attribute, turning them into multi-valued choice sets, your list will contain all values that were selected. Very handy.
But wait, there's more!
Suppose that you want to give your hypothetical shopper the ability to select more than one type of fruit or meat at a time without using
multiple, so you write some DOM-manipulating javascript to dynamically add more copies of the appropriate
select element as needed, giving each element a unique
name. (How to do this is left as an exercise for the reader. I did it, you can too.) Suppose further that you also want to give your users the ability to specify how many units of each item they want, so you add text
inputs (with appropriate input validation, of course, also left as an exercise for the reader). Give each
<input type="text"> the same
name as its corresponding
select, and you'll get a
request.POST that looks like:
{ 'fruit_0': ['4', 'cherries'], 'fruit_1': ['3', 'apples'], 'meat_0': ['1', 'buffalo'] }(In this case I'm using subscripts in my javascript to generate distinct
names. There may actually be a simpler way to do this, though I haven't hit on it yet.)
This is especially useful in the case where you have some function that you want to pass each of your (amount, item) pairs to, because then you can use the handy
*args syntax, e.g.
[doStuffTo(*thing) for thing in request.POST.values()]. You could also use a dictionary comprehension if you're using Python 3, you bleeding-edge hacker, you. Though I don't know if Django is compatible with Python 3 (and I doubt it, given all the backward-compatibility stuff that Python 3 breaks). That, too, is left as an exercise for the reader.
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