python - 高效的列表复制

Question

我有一些有效的代码，但我担心它的效率真​​的很低。是否有更高效的方法将字典列表分块/批处理到某种缓冲区中。

rowA = {1:"a",2:"b",3:"c"}         # Random dict
rowB = {4:"d",5:"e",6:"f"}         # Random dict
rowC = {7:"g",8:"h",9:"i"}         # Random dict
rowD = {0:"j",1:"k",2:"l"}         # Random dict
rows = [rowA ,rowB ,rowC ,rowD ]   # Add to a List
row_chunk = []                     # Empty List for buffer/cache
row_count = 0                      # Counter for buffer size
for row in rows:                          # Iterate over the list
    row_chunk.append(list(row.values()))  # Append the values from the dictionary
    row_count += 1                        # Increment the buffer size
    if row_count % 2 == 0:                # Check if the buffer reached level
        print("We have {0} dictionaries".format(len(row_chunk)))
        row_chunk = []                    # Reset the list

在此示例中，我将数字列表分成 2 个 block 。在生产中，我希望有 10,000 个 block ，并且 rows[] 将有 1,000,000 个条目

如前所述，这似乎确实有效，但感觉缓慢且效率低下，尤其是附加到列表并重置它。

谁能建议更好的方法。

Answer 1

将列表 A 拆分为两个:

Part1=A[:len(A)/2]
Part2=A[len(A)/2:]

我想这就是您所需要的:

>>> for row in rows:                          # Iterate over the list
...     A.append(list(row.values()))
...
>>> A=row_chunk
>>> B=A[:len(A)/2]
>>> C=A[len(A)/2:]
>>> A
[['a', 'b', 'c'], ['d', 'e', 'f'], ['h', 'i', 'g'], ['j', 'k', 'l']]
>>> B
[['a', 'b', 'c'], ['d', 'e', 'f']]
>>> C
[['h', 'i', 'g'], ['j', 'k', 'l']]

备选方案:(通过直接获取值，避免循环)

>>> rows = [rowA.values() ,rowB.values() ,rowC.values() ,rowD.values() ]   # Add to a List
>>> rows
[['a', 'b', 'c'], ['d', 'e', 'f'], ['h', 'i', 'g'], ['j', 'k', 'l']]
>>> A=rows[:len(rows)/2]
>>> B=rows[len(rows)/2:]
>>> A
[['a', 'b', 'c'], ['d', 'e', 'f']]
>>> B
[['h', 'i', 'g'], ['j', 'k', 'l']]