> Do you mean combine step 3 and step 4 together? Currently step 3 is just to compute the biggest width value and step 4 is to compute exact width and do the real format work. Only by doing real format we can get the exact width of a string. So I have to compute each width twice in both step 3 and step 4. Is combining the two steps in to one a good idea?

Sorry, Here I mean:

Do you mean combine step 3 and step 4 together? Currently step 3 is just to compute the biggest width value and step 4 is to compute exact width and do the convert work(by calling PyObject_Str()/PyObject_Repr()/PyObject_ASCII()/PyUnicode_DecodeUTF8() for %S/%R/%A/%s). Only by doing convert we can get the exact width of a string. So I have to compute each width twice in both step 3 and step 4. Is combining the two steps in to one a good idea?