test of list/dictionary reduction/union

import time
import random
import itertools
import collections

li1=[]
li2=[]
li3=[]
li4=[]
li5=[]
di1={}
di2={}
di3={}
di4={}
di5={}

for i in range(400000):
    i2=str(i)
    v=random.random()
    r1=random.random()
    r2=random.random()
    r3=random.random()
    r4=random.random()
    r5=random.random()

    if r1<.5: li1.append([i2,v])
    if r2<.5: li2.append([i2,v])
    if r3<.5: li3.append([i2,v])
    if r4<.5: li4.append([i2,v])
    if r5<.5: li5.append([i2,v])
    if r1<.5: di1[i2]=v
    if r2<.5: di2[i2]=v
    if r3<.5: di3[i2]=v
    if r4<.5: di4[i2]=v
    if r5<.5: di5[i2]=v

#method 1
start=time.time()
#stack
li=li1+li2+li3+li4+li5
groups={}
for key, group in itertools.groupby(sorted(li),lambda x:x[0]):
    groups[key] = sum([y for x, y in group])

print len(groups), time.time()-start, groups.get('1',0)

#method 2
start=time.time()
groups={}

for k in set(di1.keys()+di2.keys()+di3.keys()+di4.keys()+di5.keys()):
    groups[k]=di1.get(k,0)+di2.get(k,0)+di3.get(k,0)+di4.get(k,0)+di5.get(k,0)

print len(groups), time.time()-start, groups.get('1',0)

#method 3
start=time.time()

groups=dict( (n, di1.get(n, 0)+di2.get(n, 0)+di3.get(n, 0)+di4.get(n, 0)+di5.get(n, 0))
             for n in set(di1).union(set(di2)).union(set(di3)).union(set(di4)).union(set(di5)))
print len(groups), time.time()-start, groups.get('1',0)

#method 4
start=time.time()
#stack
li=li1+li2+li3+li4+li5
groups={}
for i in li:
    groups[i[0]]=groups.get(i[0],0)+i[1]

print len(groups), time.time()-start, groups.get('1',0)

#method 5
start=time.time()
li=li1+li2+li3+li4+li5
groups=collections.defaultdict(float)
for k, v in li:
    groups[k]+=v

print len(groups), time.time()-start, groups.get('1',0)