How to fix my python iteration?

Thank you!

Ikejrhg [~/Pycharm Projects/lkejrhg] - .../iuh.py ( iuh - Q I 1: Project Ikejrhg te iuh.py Proj... * - lkejrhg -/Pycharm Pro 1 veny bin 4 include lib Lokbsk.py #pyvenv.cfg i7y43.py te iuh.py lli External Libraries Po Scratches and Console i7y43.py x lekbsk.py x fe iuh.py i def f(n): if n=1 or n=2: return 1; else: f(n)=f(n-1)+f(n-2) No print(f(7)) * 2: Favorites Run: f() > if n juh x File "/users/aileenyoyo Li/Pycharmprojects/LKerng/lun.py", line 5 f(n)=f(n-1)+f(n-2) - SyntaxError: can't assign to function call .. 7: Structure Process finished with exit code 1 >> >> Python Console 4: Run 6: TODO Terminal Colon expected Event Log 4 spaces Python 3.7 (Ikejrhg) O 2:16 LF UTF-8