Python docx设置中文字体'NoneType' object has no attribute 'set'

Question

from docx import Document

from docx.oxml.ns import qn

doc= Document("word\shi.docx")

for p in doc.paragraphs:

for run in p.runs:
    run.element.rPr.rFonts.set(qn('w:eastAsia'), "宋体")
    

会提示'NoneType' object has no attribute 'set'

如果最后一行代码改成_element，则会提示'NoneType' object has no attribute 'rFonts'.

请问问题出在哪了？