How can I check if some checkboxes in HTML are checked?

Question

In am making a webpage in flask on which users can choose between several options. Depending on these options I want to show them their choosen options in the next page. My HTML code:

<input type="checkbox" name="name1">name1<br>
<input type="checkbox" name="name2">name2<br>
<input type="checkbox" name="name3">name3<br>

My Python code:

if checkbox 1 is checked:
    do something
if checkbox 2 is checked:
    do something different
if checkbox 3 is checked:
    do another something different

I cannot find how to form these if-statements. I found something with:

.getvalue

But then I got an error. With radio-buttons I can get it to work. When I name them all the same and give them different values with:

option = request.form['name']

However, this does also not work with checkboxes, as then it only remembers the last checkbox, but I want them all.

Solution

Each check box is unique and so is uniquely named in the form.

The values themselves can be accessed via the request.form dictionary using the name from the form as the key. For your form the checkboxes are named name1, name2, and name3. But note that they are only available if they were checked on the form, otherwise their values are not posted to the server.

So in your view function you can access them like this:

name1 = request.form.get('name1')
if name1:
    do_something(name1)

name2 = request.form.get('name2')
if name2:
    do_something(name2)

name3 = request.form.get('name3')
if name3:
    do_something(name3)

This uses get() to perform the lookup in the form dictionary. If the key is present in the dictionary the value will be returned. If the key is not in the dictionary the value None is returned.

As suggested by @Kevin Guan this can be handled in a for loop:

for checkbox in 'name1', 'name2', 'name3':
    value = request.form.get(checkbox):
    if value:
        do_something(value)

Comments

[Remi Guan]

​​​​​​​​​​​​​​​Suggestion: Put name1 and name2 and name3 into a list and use for loop instead of these three if statements.

[mhawke]

@KevinGuan: good suggestion, thanks.