gaogaotiantian commented on PR #50327:
URL: https://github.com/apache/arrow/pull/50327#issuecomment-4860959014
I'm not an expert in Cython but curious about how `result.append()` works. I
think as long as `result` is not defined as a Cython `list`, `result.append`
still works as a pure Python object? In that case, each `append` would trigger
a dynamic attribute search and the list would be reallocated a few times during
appending.
It would be an interesting experiment to do a full-allocation for the list
before assigning the data, as we already know the length of the list. An extra
step forward is to declare the return value as a list in Cython so it can
optimize `setitem` even more.
Something like
```cython
cdef list result = [None] * n
cdef Py_ssize_t i
for i in range(n):
result[i] = ...
return result
```
For a long list this might push the performance even further.
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