Python 3 for Repeat Question.

While organizing the Excel data, I have a question. The For Moon is really useful and good, but I'm having a lot of trouble coding because I don't understand it perfectly. The list of "history" is from 0 to 100, so I made it into a for moon.

The code is as follows.

for a in history:
a = int(a['price'])*float(a['qty'])
b = b+1
if (a > 49900) and (a < 50100):
    ws.cell(row=b, column=3, value=int(a))
else:
    list(a)
    for c in a:
        r = a + c
        ws.cell(row=b, column=3, value=int(r))

Assume that the list 'history' has key values of 'price' and 'qty', and in the for statement

if (a > 490000) and (a <50100):
ws.cell(row=b, column=3, value=int(a))

The above conditions have been created. What I'm curious about here is that if you enter Excel in order from the list of 'history' and get a value lower than the above conditions, I want to print it out when the value is between 49900 and 50100 in one row.

But I wonder how I can remember the next value and add it together to print it out.