合並兩個列表的Python方式

Question

我想將值附加到現有字典中。 這是我的代碼：

tmp_result = [{'M': 8}, {'N': 16},]
cross_configs = [({'device': 'cpu'},), ({'device': 'cuda'},)]

import copy
generated_configs = []
for config in cross_configs:
    for value in config:
            new_value = copy.deepcopy(tmp_result)
            new_value.append(value)
            generated_configs.append(new_value)

print (generated_configs)

Output: 
[[{'M': 8}, {'N': 16}, {'device': 'cpu'}], [{'M': 8}, {'N': 16}, {'device': 'cuda'}]]

我不喜歡進行深度復制和追加的內部循環。 什么是Python的方式做到這一點？

Answer 1

您可以進行列表理解：

[tmp_result + list(x) for x in cross_configs]

范例 ：

tmp_result = [{'M': 8}, {'N': 16},]
cross_configs = [({'device': 'cpu'},), ({'device': 'cuda'},)]

print([tmp_result + list(x) for x in cross_configs])
# [[{'M': 8}, {'N': 16}, {'device': 'cpu'}], [{'M': 8}, {'N': 16}, {'device': 'cuda'}]]

Answer 2

嵌套列表理解就足夠了； 給出顯示的示例，對dict的顯式調用就足以避免需要進行deepcopy 。

generated_configs = [[dict(y) for y in tmp_result + list(x)] for x in cross_configs]

如果您反對tmp_result + list(x) ，請改用itertools.chain 。

from itertools import chain
generated_configs = [[dict(y) for y in chain(tmp_result, x)] for x in cross_configs]