#!/usr/bin/env python3
import xlwings as xw
import pandas as pd

wb = xw.Book()  # this will open a new workbook
wb = xw.Book('FileName.xlsx')  # connect to a file that is open or in the current working directory
sheet = wb.sheets['Sheet1']


df = pd.DataFrame([[1,2], [3,4]], columns=['a', 'b'])
sheet['A1'].value = df
sheet['A1'].options(pd.DataFrame, expand='table').value


@xw.func
@xw.arg('x', pd.DataFrame)
def correl2(x):
    # x arrives as DataFrame
    return x.corr()