Well, since what you want to do is not "standard" scientific notation, I'm not sure if there is a simple call to do this. Here is a hack, however, that will work
a = 1234567890e12
A = str(a)
exp = A.find('e+')
converted = '0.' + A[0] + A[2:exp] + 'e+' + str(int(A[exp+2:])+1)