问题描述
我编写了一个函数，该函数使用csv模块将字典列表序列化为CSV文件，其代码如下:
I wrote a function that serializes a list of dictionaries as a CSV file using the csv module, with code like this:
data = csv.DictWriter(out_f, fieldnames)
data.writerows(dictrows)
但是，有时我只想将每个字典键的一个子集写到文件中.如果我以fieldnames的形式传递每个字典具有的键的子集，则会收到错误消息:
However, I sometimes want to write out to a file only a subset of each dictionary's keys. If I pass as fieldnames a subset of the keys that each dictionary has, I get the error:
"dict contains fields not in fieldnames"
如何做到这一点，以便DictRows仅将我指定的字段的子集写入CSV，而忽略字典中但字段名中没有的那些字段?
How can I make it so that DictRows will write just a subset of the fields I specify to CSV, ignoring those fields that are in the dictionary but not in fieldnames?
推荐答案
最简单，最直接的方法是在初始化DictWriter实例时通过extrasaction='ignore'，如此处:
Simplest and most direct approach is to pass extrasaction='ignore' when you initialize your DictWriter instance, as documented here:
它也可以在writerows上运行，在内部，它只是重复调用writerow.
It also works on writerows, which, internally, just calls writerow repeatedly.
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