i'm basically trying to add values 1-100 in combo box but i'm unable to do so
for i in range(1,100):
rollno_list = []
rollno_list.append(i)
combo_roll = QComboBox()
combo_roll.addItems([str(rollno_list)])
You are adding a list with a single element that is a string, instead you must convert each element to a string:
combo_roll.addItems([str(e) for e in range(1, 100)])
Also in the for-loop you are creating a list in each iteration where you add a new element which is an error.