如何在pymongo中将特定属性的所有值设置为小写

Question

I am using pymongo to update attributes in a mongodb database. I have an attribute gender, which contains, for example, male MALE and Male, and i need those to match. I have tried:

mongo_collection.aggregate([{ $project: { Gender:{ $toLower:"$Gender"}, src:1}}])

but it said the sytax was invalid.

Let me know if you have any insight on why the syntax is invalid?

Answer 1

I am using pymongo 3.6 and have been doing such queries there. I think the first mistake is you haven't enclosed '$toLower' in quotes ''. If you haven't defined Gender variable somewhere you might need to enclose that as well in quotes. For me the working syntax is below -

mycoll.aggregate([{'$project':{'itemName':{'$toUpper':'$item'},'itemNo':1}}])

If i leave $toUpper without quotes , it tells me invalid syntax at $ and i think its same what you are encountering.