Syntaxerror: "Can't Assign to Function Call"

Syntactically, this line makes no sense:

invest(initial_amount,top_company(5,year,year+1)) = subsequent_amount

You are attempting to assign a value to a function call, as the error says. What are you trying to accomplish? If you're trying set subsequent_amount to the value of the function call, switch the order:

subsequent_amount = invest(initial_amount,top_company(5,year,year+1))

You wrote the assignment backward: to assign a value (or an expression) to a variable you must have that variable at the left side of the assignment operator ( = in python )

subsequent_amount = invest(initial_amount,top_company(5,year,year+1))

You are assigning to a function call:

invest(initial_amount,top_company(5,year,year+1)) = subsequent_amount

which is illegal in Python. The question is, what do you want to do? What does invest() do? I suppose it returns a value, namely what you're trying to use as subsequent_amount, right?

If so, then something like this should work:

amount = invest(amount,top_company(5,year,year+1),year)