使用Python lambda时处理缺少的字段

Question

我有这个rethinkDB查询，它基本上返回了＆＃34; basicConstraints＆＃34;以＆＃34; CA开头的字段：FA＆＃34;。

然而，在我的一些文件中，＆＃34; basicConstraints＆＃34;字段不存在。

q = r.db('scanafi').table(active_table) \
.concat_map(lambda doc: doc["certificates"]\
.concat_map(lambda x: x["parsed_certificate"]["X509 extensions"])\
    .filter(lambda x: x["basicConstraints"]
.match("^CA:FA"))) \
.run()

如何在查询中包含所有包含此缺少字段的文档？

Answer 1

It seems that your x doesn't have methods like a regular python dict (I'm not familiar with rethinkdb). You could just use a real function here, with a try/except clause:

def basic_constraints(x):
    try:
        return x["basicConstraints"]
    except:  # find out what the actual exception is and put that here
        return True

q = r.db('scanafi').table(active_table) \
.concat_map(lambda doc: doc["certificates"]\
.concat_map(lambda x: x["parsed_certificate"]["X509 extensions"])\
    .filter(basic_constraints)
.match("^CA:FA"))) \
.run()## Heading ##

Answer 2

您可以撰写x.has_fields('basicConstraints').not().or_(x['basicConstraints'].match("^CA:FA"))。