CODEWITHSUNDEEP
pythondictionarycoding-style
Dmitry Belaventsev
Dmitry Belaventsev

Reputation: 6657

Dictionary: key exist or not

I use django to build my web app. And one of the page sends different files (with different file types). I have 6 file type. And my current version of code (it's really bad - that is why I write this question) is:

    try:
        file = request.FILES[u'file_doc']
    except MultiValueDictKeyError:
        try:
            file = request.FILES[u'file_fb2']
        except MultiValueDictKeyError:
            try:
                file = request.FILES[u'file_pdf']
            except MultiValueDictKeyError:
                try:
                    file = request.FILES[u'file_txt']
                except MultiValueDictKeyError:
                    try:
                        file = request.FILES[u'file_other']
                    except MultiValueDictKeyError:
                        try:
                            file = request.FILES[u'file_chm']
                        except MultiValueDictKeyError:
                            return HttpResponse('bad file type')

Could you advise me - how to improve this bad peace of code.

TIA!

Upvotes: 0

Views: 575

Answers (4)

Martijn Pieters
Martijn Pieters

Reputation: 1124110

The in test let's you see if a key is part of a dictionary.

if u'file_doc' in request.FILES:
    file = request.FILES[u'file_doc']

You can simply loop through a set of keys to test for:

for key in (u'file_doc', u'file_fb2', .. ):
    if key in request.FILES:
        file = request.FILES[key]
        break
else:
    return HttpResponse('bad file type')

The else suite will only be executed if the for loop completed without reaching a break statement, i.e. you didn't find a matching key.

Note that you could still use your exception approach in the loop:

for key in (u'file_doc', u'file_fb2', .. ):
    try:
        file = request.FILES[key]
        break
    except MultiValueDictKeyError:
        pass
else:
    return HttpResponse('bad file type')

but I am not so sure that is more readable.

Upvotes: 6

Joran Beasley
Joran Beasley

Reputation: 114038

def GetFile(request):
    file_types = "doc fb2 pdf txt other chm".split()
    for k in file_types:
        if "file_{0}".format(k) in request.FILES:
             return request.FILES["file_{0}".format(k)]

at least thats how I would do it

Upvotes: 1

larsks
larsks

Reputation: 312370

You could do something like this:

filetypes = [ u'file_doc', u'file_fb2', u'file_pdf' ]

file = None
for ft in filetypes:
  if ft in request.FILES:
    file = request.FILES[ft]
    break

if file is None:
  return HttpResponse('bad file type')

Upvotes: 3

gsk
gsk

Reputation: 578

request.FILES.get(u'file_doc', DEFAULT_VALUE) will return DEFAULT_VALUE if the key does not exist in the dictionary. You can also use the in keyword as mentioned by Martijn edit see also django MultiValueDictKeyError error, how do i deal with it

Upvotes: 2

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