python scientific notation with forced leading zero

问题

I want to have Python2.7 print out floating point numbers in scientific notation, forced to start with 0. For instance, assume

a=1234567890e12
print '{:22.16E}'.format(a)
1.2345678900000000E+21

However, I want a print output that looks like:

0.1234567890000000E+22

Notice that the exponent is raised by one since the desired output is forced to a leading zero. How can I achieve this? Thanks.

回答1:

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)

回答2:

The fortranformat package will do what you are looking for.

import fortranformat as ff

a=1234567890e12
lineformat = ff.FortranRecordWriter('(1E26.16)')
lineformat.write([a])

Output:

'    0.1234567890000000E+22'

来源：https://stackoverflow.com/questions/21266850/python-scientific-notation-with-forced-leading-zero