Python

Question

我有一个二维列表，其中分别包含足球运动员的姓名、他们进球的次数以及他们尝试射门的次数。

player_stats = [['Adam', 5, 10], ['Kyle', 12, 18], ['Jo', 20, 35], ['Adam', 15, 20], ['Charlie', 31, 58], ['Jo', 6, 14], ['Adam', 10, 15]]

从这个列表中，我正在尝试 return 另一个列表，该列表仅显示每个玩家的一个实例及其各自的总个目标和总计次射门尝试，如下所示：

player_stats_totals = [['Adam', 30, 45], ['Kyle', 12, 18], ['Jo', 26, 49], ['Charlie', 31, 58]]

在 Stack Overflow 上搜索后，我能够（从）学习如何 return 重复玩家的索引

x = [player_stats[i][0] for i in range (len(player_stats))]

for i in range (len(x)):
    if (x[i] in x[:i]) or (x[i] in x[i+1:]): print (x[i], i)

但在之后的处理方式上卡住了，如果这个方法确实与我需要的完全相关(?)

return 所需总计列表的最有效方法是什么？

Answer 1

使用字典来累积给定玩家的值：

player_stats = [['Adam', 5, 10], ['Kyle', 12, 18], ['Jo', 20, 35], ['Adam', 15, 20], ['Charlie', 31, 58], ['Jo', 6, 14], ['Adam', 10, 15]]

lookup = {}
for player, first, second in player_stats:
    
    # if the player has not been seen add a new list with 0, 0 
    if player not in lookup:
        lookup[player] = [0, 0]
    
    # get the accumulated total so far 
    first_total, second_total = lookup[player]
    
    # add the current values to the accumulated total, and update the values 
    lookup[player] = [first_total + first, second_total + second]

# create the output in the expected format
res = [[player, first, second] for player, (first, second) in lookup.items()]
print(res)

输出

[['Adam', 30, 45], ['Kyle', 12, 18], ['Jo', 26, 49], ['Charlie', 31, 58]]

一个更高级的，pythonic，版本是用collections.defaultdict:

from collections import defaultdict

player_stats = [['Adam', 5, 10], ['Kyle', 12, 18], ['Jo', 20, 35],
                ['Adam', 15, 20], ['Charlie', 31, 58], ['Jo', 6, 14], ['Adam', 10, 15]]

lookup = defaultdict(lambda: [0, 0])
for player, first, second in player_stats:
    # get the accumulated total so far
    first_total, second_total = lookup[player]

    # add the current values to the accumulated total, and update the values
    lookup[player] = [first_total + first, second_total + second]

# create the output in the expected format
res = [[player, first, second] for player, (first, second) in lookup.items()]

print(res)

这种方法的优点是跳过初始化。两种方法都是 O(n)。

备注

表达式：

res = [[player, first, second] for player, (first, second) in lookup.items()]

是一个list comprehension，相当于下面的for循环：

res = []
for player, (first, second) in lookup.items():
    res.append([player, first, second])

此外，阅读 this 以了解解包。

Answer 2

你想要做的是使用一个字典，其中键是球员姓名，值是包含 [goals, shots] 的列表。构建它看起来像这样：

all_games_stats = {}
for stat in player_stats:
    player, goals, shots = stat
    if player not in all_games_stats:
        all_games_stats[player] = [goals, shots]
    else:
        stat_list = all_games_stats[player]
        stat_list[0] += goals
        stat_list[1] += shots

然后，如果您想将球员及其统计数据表示为列表，您可以这样做：列表（all_games_stats.items（））

Answer 3

您可以将列表转换为字典。（它总是可以在完成后改回）这个有效：

player_stats = [['Adam', 5, 10], ['Kyle', 12, 18], ['Jo', 
20, 35], ['Adam', 15, 20], ['Charlie', 31, 58], ['Jo', 6, 
14], ['Adam', 10, 15]]

new_stats = {}


for item in player_stats:
    if not item[0] in new_stats:
        new_stats[item[0]] = [item[1],item[2]]
    else:
        new_stats[item[0]][0] += item[1]
        new_stats[item[0]][1] += item[2]

print(new_stats)

Answer 4

我也不妨提交一些东西。这是另一种具有一些列表理解功能的方法：

# Unique values to new dictionary with goal and shots on goal default entries 
agg_stats = dict.fromkeys(set([p[0] for p in player_stats]), [0, 0])

# Iterate over the player stats list
for player in player_stats:
    # Set entry to sum of current and next stats values for the corresponding player.
    agg_stats[player[0]] = [sum([agg_stats.get(player[0])[i], stat]) for i, stat in enumerate(player[1:])]

Answer 5

另一种方式，将整个三元组（包括名称）存储在字典中并更新它们：

stats = {}
for name, goals, attempts in player_stats:
    entry = stats.setdefault(name, [name, 0, 0])
    entry[1] += goals
    entry[2] += attempts
player_stats_totals = list(stats.values())

还有一个有趣的复数解决方案，这使得添加很好但需要烦人的转换回来：

from collections import defaultdict

tmp = defaultdict(complex)
for name, *stats in player_stats:
    tmp[name] += complex(*stats)
player_stats_totals = [[name, int(stats.real), int(stats.imag)]
                       for name, stats in tmp.items()]

Python - 二维列表 - 在一列中查找重复项并在另一列中求和值

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