from collections import defaultdict
from itertools import groupby

def lauritz(lst):
    key = lambda dct: dct['id']
    lst.sort(key=key)
    ret = []
    for key, group in groupby(lst, key=key):
        ret.append(max(group, key=lambda dct: dct['s']))
    return ret

def ashwini(lst):
    dic={}
    for x in lst:
        idx=x['id']
        if dic.get('s',float('-inf')) < x ['s']:
            dic[idx]=x
    return dic.values()

def martijn(lst):
    per_id = defaultdict(list)

    for entry in lst:
        per_id[entry['id']].append(entry)

    output = [max(v, key=lambda d: d['s']) for v in per_id.itervalues()]
    return output

def thijs(lst):
    seen = set()
    output = [d for d in sorted(lst, key=lambda d: d['s'], reverse=True)
          if d['id'] not in seen and not seen.add(d['id'])]
    return output

def jamylak(lst):
    res = {}
    for d in lst:
        id_ = d['id']
        res[id_] = max(res.get(id_, {}), d, key=lambda x: x.get('s', float('-inf')))
    return res.values()

import random
import time

results = {}
index = []
for lst_len_pow in range(5, 19):
    lst_len = 2 ** lst_len_pow
    index.append(lst_len)
    lst = [{
        'id': random.randint(1, 10),
        's': random.uniform(0, 5)} for x in range(lst_len)]
    for func in (lauritz, ashwini, martijn, thijs, jamylak):
        start = time.time()
        func(lst)
        results.setdefault(func.__name__, []).append(time.time() - start)

import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame(results, index=index)
df.plot()
plt.loglog()
plt.xlabel("list lenght")
plt.ylabel("execution time")
plt.show()