Should I ask for a contract as sublettee?

Accomodation, House and Garden
1
I'm looking for a sublet furnished apartment in Zürich.

I wonder if I should ask for a formal contract, or if it's an informal agreement.

I wouldn't feel comfortable without a contract, but I don't know what is the current practice.

2
To avoid problems always ask for a contract.

https://www.ch.ch/en/concluding-rental-agreement/