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djangolistrequest
andyw
andyw

Reputation: 3773

django request.POST.getlist[my_list', None] returns [] for non-existant keys

I'm using Django 1.10.2.

In a view, the below return []

    print(request.POST.getlist('collected_already', None))
    print(request.POST.getlist('collected_already[]', None))
    print(request.POST.getlist('non_existent', None))
    print(request.POST.getlist('non_existent[]', None))

I would expect None to be returned for the non_existent keys, and [] returned when an empty list is sent.

My workaround is to send and detect ['blank'] instead of [].

I'd appreciate pointers. With best wishes, Andy.

Upvotes: 2

Views: 3729

Answers (2)

Kishan Mehta
Kishan Mehta

Reputation: 2678

I think getlist() takes default argument as None and returns empty list [ ] if key is not found.

Check this

Returns the data with the requested key, as a Python list. Returns an empty list if the key doesn’t exist and no default value was provided. It’s guaranteed to return a list of some sort unless the default value provided is not a list.

Upvotes: 0

Alasdair
Alasdair

Reputation: 308999

The getlist returns the empty list [] by default. If you pass default=None, then that is treated as 'no default specified', not as 'default to None`.

If you want to coerce the empty list [] to None, then you could simply add or None to the end of the expression.

print(request.POST.getlist('collected_already') or None)

This works because of the way Python evaluates boolean expressions. If x and y both evaluate to False, then x or y returns y.

Upvotes: 6

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