fh = open('mbox-short.txt')
#The 'mbox-short.txt' file can be downloaded from the link: https://www.py4e.com/code3/mbox-short.txt
sum = 0
count = 0
for fx in fh:
	fx = fx.rstrip()
	if not fx.startswith("X-DSPAM-Confidence:") :
		continue
	fy = fx[19:]
	count = count + 1
	sum = sum + float(fy)
print ('Average spam confidence: ',sum/count)