Python Form a List based from the values in dictionary

Question

i'm new to python I have Ordered dictionary

dictA = {f1 : ["s","r"], 
        f2 : ["p"], 
        f3 : ["w","t"]}

How do I form a list that should have only 1st elements from values present in dictionary dictA and followed by 2nd elements ... and so on, until it reached the list_size_limit = 5

Final list ["s","p","w","r","t"]

if the list_size_limit = 3

Final list = ["s","p","w"]

How do i form a list which has 1st elements of all values of dictionary to be present in list 1st, followed by 2nd elements...3rd elements

What have you tried, and what precisely is the problem with it? Note that you can't guarantee output order of values from a dictionary, it's not clear whether you need that. — jonrsharpe, Mar 28 '16 at 07:56
There's an inherent problem with this question. Dictionaries are unordered on their keys, so `list` with `list_size_limit == 3` could be any permutation of `{"s", "p", "w"}`. [`OrderedDict`](https://docs.python.org/3/library/collections.html#collections.OrderedDict) can help with that at least. — Alyssa Haroldsen, Mar 28 '16 at 08:00
I need all the 1st elements of all values of dictionary to be present in list 1st, followed by 2nd elements...3rd elements — FryMan, Mar 28 '16 at 08:17
"i have Orderdict() dictA is ordered" Please add this to the question. — Stop harming Monica, Mar 28 '16 at 08:19

score 2 · Answer 1 · answered Mar 28 '16 at 08:21

Honestly not sure what to call this function. Naming things is hard.

def getFirstOfDictList(d, limit=None):
    if limit is None:
        limit = float('inf')
    done = 0
    iters = [iter(i) for i in d.values()]
    items = []
    while iters:
        toRemove = []
        for iterator in iters:
            if done >= limit:
                return items
            try:
                items.append(next(iterator))
                done += 1
            except StopIteration:
                toRemove.append(iterator)
        for finishedIterator in toRemove:
            iters.remove(finishedIterator)
    return items

any alternative way to solve ? With out creating iter object — FryMan, Mar 29 '16 at 15:27

score 0 · Accepted Answer · answered Mar 30 '16 at 04:26

dictA = {"f1" : ["m"],
        "f2" : ["p","y","o","a","s","d","f","g"],
        "f3" : ["w","t"],
         "f5" : ["z","x"],
         "f6" : ["c","v"]}

result = []
limit_size = 3
values_list = []
for values in dictA.itervalues():
    values_list.append(len(values))

for i in range(0,max(values_list)):
    keys = list(dictA.keys())
    count = 0
    while count < len(keys):
        try:
            result.append(dictA[keys[count]][i])
        except IndexError:
            dictA.pop(keys[count])
        count = count + 1
print "final ",result[0:limit_size]

Python Form a List based from the values in dictionary

2 Answers2