>>> '{0:+} number'.format(1)
'+1 number'
>>> '{0:+} number'.format(-1)
'-1 number'
>>> '{0:+} number'.format(-37)
'-37 number'
>>> '{0:+} number'.format(37)
'+37 number'
# As the questions ask for it, little trick for not printing it on 0
>>> number = 1
>>> '{0:{1}} number'.format(number, '+' if number else '')
'+1 number'
>>> number = 0
>>> '{0:{1}} number'.format(number, '+' if number else '')
'0 number'