end = smooth(data,window_len=40)
plot.plot(time[0:len(end)],end)
plot.savefig('hanning(40).pdf') #problem line

plot.savefig('hanning',num,'.pdf')

plot.savefig('hanning(%d).pdf' % num)

plot.savefig('hanning' + str(num) + '.pdf')

plot.savefig('hanning%s.pdf' % num)

plot.savefig('hanning%(num)s.pdf' % locals()) # Neat trick

plot.savefig('hanning{0}.pdf'.format(num)) # Note: This is the new preferred way

plot.savefig(f'hanning{num}.pdf') # added in Python 3.6

plot.savefig(string.Template('hanning${num}.pdf').substitute(locals()))

>>> name = "Fred"
>>> f"He said his name is {name}."
'He said his name is Fred.'

plot.savefig(f'hanning{num}.pdf')

"hello " + str(10) + " world" = "hello 10 world"

stringExample = "someString " + str(someNumber)
print(stringExample)
plot.savefig(stringExample)

['file' + str(i) + '.pdf' for i in range(1,4)]

nums = [1,2,3]
plot.savefig('hanning{0}{1}{2}.pdf'.format(*nums))