ValueError: invalid literal for int() with base 10: ''

Why it showing the error of int(), in fact the values coming from the cgi is as string which i am converting it to integer, bcoz my comparable part variable actual_ans_dict contains an integer

res12 = form.getvalue('opt_12', '')
res27 = form.getvalue('opt_27', '')
res20 = form.getvalue('opt_20', '')
res16 = form.getvalue('opt_16', '')
res13 = form.getvalue('opt_13', '')
res19 = form.getvalue('opt_19', '')
res25 = form.getvalue('opt_25', '')actual_ans_dict = {}
count = 0
b = []
for data in prsnobj.result:actual_ans_dict[data[0]] = data[1]#print actual_ans_dict[12], actual_ans_dict[27], actual_ans_dict[20],     actual_ans_dict[16], actual_ans_dict[13], actual_ans_dict[19], actual_ans_dict[25]if int(res12) == actual_ans_dict[12]:count += 1
if int(res27) == actual_ans_dict[27]:count += 1
if int(res20) == actual_ans_dict[20]:count += 1
if int(res16) == actual_ans_dict[16]:count += 1
if int(res13) == actual_ans_dict[13]:count += 1
if int(res19) == actual_ans_dict[19]:count += 1
if int(res25) == actual_ans_dict[25]:count += 1
if count:b.append(count)if len(b)==0:print "Fail"else:print "Marks: ", b

The problem is because int tries to convert '' to a base 10 number, which is not possible. Thats why it is failing. You are getting the default '' if the value is not there like this

form.getvalue('opt_12', '')

instead of that use a sentinel value like this

form.getvalue('opt_12', '0')

Even better, you can convert them to numbers as and when you get them from the form like this

res12 = int(form.getvalue('opt_12', '0'))
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