I parked a $1200 bike 3 days a week on the streets of SF and I used the following lock
https://www.amazon.com/gp/product/B06XS44H58/
I notice at least 3 times someone tried to cut it with cutters and couldn't do it. Well worth the $140ish it costs. If you get a chain or cable lock your bike will be lucky to last a few weeks before it's gone.
This lock is expensive. But will most definitely keep it safe from your average shitter theif. https://www.amazon.com/dp/B06XS44H58/ref=cm_sw_r_cp_awdb_btf_t1_QLWtFb0CRFBZB
I bought this lock: https://www.amazon.com/gp/product/B06XS44H58/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1
It is expensive and the price has actually gone up since I purchased it. That said, it is light weight, durable, and doesn't clank around in the mounting clip.