import urllib.request, urllib.parse, urllib.error

img = urllib.request.urlopen('http://data.pr4e.org/cover3.jpg')
man_a = open('portada.jpg', 'wb')
tamano = 0
while True:
    info = img.read(100000)
    if len(info) < 1: break
    tamano = tamano + len(info)
    man_a.write(info)

print(tamano, 'caracteres copiados.')
man_a.close()