sorted by value in dict python

lis = [['2016-10-01,83928373'],['2016-10-01,83928373'],['2016-10-02,93928373'],['2016-10-01,234242'],['2016-10-02,90384102']]

dict_day = {}
list_a = []
list_b = []
for tmp in lis:
tmp = tmp[0]
list_a = tmp.split(',')
a = list_a[0]
b = list_a[1]
list_b.append(a)

dict_day.setdefault(a,[]).append(b)

list_max = []
dict_max = {}
for i in list_b:
list_r = [int(t) for t in dict_day[i]]
list_r.sort(reverse=True)
a = list_r[0]
dict_max[i] = a
list_max.append(a)

for key in dict_day:

sorted_x = sorted(dict_max.iteritems(), key=lambda dict_max : dict_max[1], reverse=True)

list_sort = list(sorted_x)
list_1 = [list(i) for i in sorted_x]
print list_1
for i in list_1:
list_2 = [str(t) for t in i]
print list_2[0]+","+list_2[1]

print ','.join(list(sorted_x[0]))

list_max.sort(reverse=True)