<input type="hidden" id="list_id" name="list_id" value="1,2,3,4,5,6,7,8,9,10">
list_id = request.form.getlist('list_id')
for i in list_id:
print(type(i))
print(i)
<class 'str'>
1,2,3,4,5,6,7,8,9,10
<class 'str'>
1
<class 'str'>
2
<class 'str'>
3
<class 'str'>
4