I think the line

if price * shares > cash:

might be problematic on multiple stages.

Here, price would be the float, and shares the sequence.

shares is probably a string and needs conversion to integer first (also reject it if it contains any non-digit)

cash is a list of dicts, most likely containing exactly one dict with one value. The value you want is probably at cash[0]["cash"].

I think the line

if price * shares > cash:

might be problematic on multiple stages.

Here, price would be the float, and shares the sequence.

shares is probably a string and needs conversion to integer first (also reject it if it contains any non-digit)

cash is a list of dicts, most likely containing exactly one dict with one value. The value you want is probably at cash[0]["cash"].

Your app is in debug mode. Within werkzeug's debug mode, you can open a python console at where the crash happened, printing the variables and experiencing some surprise from time to time.