Sending a form array to Flask

You are following a PHP convention of adding brackets to the field names. It's not a web standard, but because PHP supports it out of the box it is popular; Ruby on Rails also uses it.

If you do use that convention, to get the POST data on the Flask side you need to include the square brackets in the field name. You can retrieve all values of the list using MultiDict.getlist():

hello = request.form.getlist('hello[]')

You don't have to use the [] convention at all, of course. Not appending the [] to the hello name will work perfectly fine, at which point you'd use request.form.getlist('hello') in Flask.

I written a parse function which supports multidimensional dict:php_post=parse_multi_form(request.form)

def parse_multi_form(form):
    data = {}
    for url_k in form:
        v = form[url_k]
        ks = []
        while url_k:
            if '[' in url_k:
                k, r = url_k.split('[', 1)
                ks.append(k)
                if r[0] == ']':
                    ks.append('')
                url_k = r.replace(']', '', 1)
            else:
                ks.append(url_k)
                break
        sub_data = data
        for i, k in enumerate(ks):
            if k.isdigit():
                k = int(k)
            if i+1 < len(ks):
                if not isinstance(sub_data, dict):
                    break
                if k in sub_data:
                    sub_data = sub_data[k]
                else:
                    sub_data[k] = {}
                    sub_data = sub_data[k]
            else:
                if isinstance(sub_data, dict):
                    sub_data[k] = v

    return data

Usage:

>>> request.form={"a[0][name]": "ahui", "a[0][sex]": "female", "a[1][name]": "bhui", "a[1][sex]": "male"}
>>> parse_multi_form(request.form)
{'a': {0: {'name': 'ahui', 'sex': 'female'}, 1: {'name': 'bhui', 'sex': 'male'}}}

Warnning: It does not support list,e.g. a[][0]=1&a[][0]=2, it may make programmer to be confused. Either a=[[1,2]] or a[[1],[2]] is too hard to choose.

So I suggest use dict to replace list:

<input name="hello[0]" type="text" />
<input name="hello[1]" type="text" />

If you still want to post complex data, I suggest you use application/json