If you just want a string with the value: 'I am going {nuts}'.format(nuts= 'crazy over this')
Try encapsulating it in double quotes like this:
s = "'I am going {nuts}'.format(nuts= 'crazy over this')"
Or you might need to somehow concatenate the string like this:
s = 'I am going {wild} ' + '{nuts}'.format(nuts= 'crazy {nutty} over this') + ' for real!'
print s
'I am going {wild} crazy {nutty} over this for real!'