The whole concept of interns in Sweden is different compared to the US. Here you intern while you study or even as a part of your education. There are a few smaller startups that are looking for interns sometimes. Most likely unpaid though.
Temporary contracts are more common. I'm currently on a 4 month contract at a huge telecom company.
My suggestion would be to just google whatever you want to work with and add Stockholm to the search. Most companies here have some kind of English homepage. If not - look for; Lediga jobb, Lediga tjänster, Karriär, Jobba hos oss.
Those are probably the most common ways of saying "Work with us" or "Available positions". After that you just look for job ads with words or programming languages you recognize.
I live in Stockholm, actually from here. Maybe I can help you out, at least a little bit.
First off, not speaking Swedish is fine. Almost anyone above the age of 7 speak English well enough. And second, since you are a French citizen you are allowed to work here without to much trouble.
I'm sure a lot of companies would love the help, hell I could use it myself. But Stockholm is not all good.
It's extremely expensive and interns (praktikanter in Swedish) are not paid. At least I've never heard of one that get paid.
You'll need a lot of resources and somewhere to live before you get here. Apartments in the city or close to it are hard to come by.
I could go on forever. But the bottom line is. Sweden and Stockholm are a great place to be but it's expensive and you need to be ready for it.
Temporary contracts are more common. I'm currently on a 4 month contract at a huge telecom company.
My suggestion would be to just google whatever you want to work with and add Stockholm to the search. Most companies here have some kind of English homepage. If not - look for; Lediga jobb, Lediga tjänster, Karriär, Jobba hos oss. Those are probably the most common ways of saying "Work with us" or "Available positions". After that you just look for job ads with words or programming languages you recognize.
Good luck!