I have a DOCX file, which has the following info

	pages of section	header
section 1	1	None
section 2	2	Abstract. current page ??, total IV pages
section 3	5	paper body, current page ??, total 35 pages

Then if the line oSec.Headers(1).Range.Fields.Update is used in the following VBA code, the corrected header text will be shown

Function myTrim(s)
    a = Replace(s, vbLf, "")
    myTrim = Trim(a)
End Function

Sub displayHeader()
    idx = 1
    For Each oSec In ActiveDocument.Sections
		oSec.Headers(1).Range.Fields.Update 'this line must be called
        MsgBox "sec " & idx & " " & myTrim(oSec.Headers(1).Range.Text)
        idx = idx + 1
    Next
End Sub

Then I coined the Python version, as we all know it looks like the original VBA one

import win32com
from win32com.client import Dispatch, constants

#~ word = win32com.client.Dispatch('Word.Application')

word = win32com.client.gencache.EnsureDispatch('Word.Application')

word.Visible = 1
word.DisplayAlerts = 0

word.Documents.Open('r:/test.docx')

for idx, oSec in enumerate(word.ActiveDocument.Sections):
    #~ oSec.Headers(1).Range.Fields.Update()
    print(f'sec {idx+1}', oSec.Headers(1).Range.Text.strip())

word.Documents.Close(constants.wdDoNotSaveChanges)
word.Quit()

However the Python code does not give the same corrected header text:

	Dispatch('Word.Application')	gencache.EnsureDispatch('Word.Application')
use Range.Fields.Update()	sec 1 sec 2 Abstract. current page I, total I pages sec 3 paper body, current page 1, total 1 pages	sec 1 sec 2 Abstract. current page I, total I pages sec 3 paper body, current page 1, total 1 pages
do not use Range.Fields.Update()	sec 1 sec 2 Abstract. current page III, total IV pages sec 3 paper body, current page 1, total 35 pages	sec 1 sec 2 Abstract. current page I, total I pages sec 3 paper body, current page 1, total 35 pages

So, what is the problem, and how to fix it? Thank you in advance.