fix - zero float number for log, set ef_construction arg for Build(), remove whitespace

[kwangswei]

Thanks for your contribution :) Before you submit this pull request, please ensure it is against the dev branch and not master.

• [v] ensure branch where you submitting, it sould be dev.
• [v] check your coding convension.
  • 4 spaces for indentation
  • pep8 for Python