python-docx把dataframe表格添加到word文件中思路较为简单：

1. 先把dataframe格式转变为table
2. 新建一个段落：document.add_paragraph()
3. 把table添加到这个段落下方

效果图

示例代码

from docx import Document, oxml
import pandas as pd
import numpy as np
from docx.oxml.ns import qn
from docx.oxml import OxmlElement
import random


# 设置 table 的边框，用法与 cell 类似
def set_table_boarder(table, **kwargs):
    """
    Set table`s border
    Usage:
    set_table_border(
        cell,
        top={"sz": 12, "val": "single", "color": "#FF0000"},
        bottom={"sz": 12, "color": "#00FF00", "val": "single"},
        left={"sz": 24, "val": "dashed"},
        right={"sz": 12, "val": "dashed"},
    )
    """
    borders = OxmlElement('w:tblBorders')
    for tag in ('bottom', 'top', 'left', 'right', 'insideV', 'insideH'):
        edge_data = kwargs.get(tag)
        if edge_data:
            any_border = OxmlElement(f'w:{tag}')
            for key in ["sz", "val", "color", "space", "shadow"]:
                if key in edge_data:
                    any_border.set(qn(f'w:{key}'), str(edge_data[key]))
            borders.append(any_border)
            table._tbl.tblPr.append(borders)
    return table


def set_table_singleBoard(table):
    """为表格添加边框"""
    return set_table_boarder(
        table,
        top={"sz": 4, "val": "single", "color": "#000000"},
        bottom={"sz": 4, "val": "single", "color": "#000000"},
        left={"sz": 4, "val": "single", "color": "#000000"},
        right={"sz": 4, "val": "single", "color": "#000000"},
        insideV={"sz": 4, "val": "single", "color": "#000000"},
        insideH={"sz": 4, "val": "single", "color": "#000000"}
    )


def convert_df_to_table(document, dataframe: pd.DataFrame, index_list=None, column_list=None):
    """把table转为dataframe
    :param document: 文档对象
    :param dataframe: dataframe格式数据
    :param index_list: 最左边一列显示的内容
    :param column_list: （第一行）列名称需要显示的内容
    """
    rows = dataframe.shape[0]
    cols = dataframe.shape[1]
    if index_list is not None:
        cols += 1
    if column_list is not None:
        rows += 1
    table = document.add_table(rows=rows, cols=cols)
    row_i = 0
    col_i = 0
    if index_list is not None:
        raise
    if column_list is not None:
        hdr_cells = table.rows[row_i].cells
        for _col_i, _v in enumerate(column_list):
            hdr_cells[_col_i].text = str(_v)
        row_i += 1
    for _i, series_info in enumerate(dataframe.iterrows()):
        series = series_info[1]
        hdr_cells = table.rows[row_i + _i].cells
        for _c_i, _cell_value in enumerate(series):
            hdr_cells[col_i + _c_i].text = str(_cell_value)
    return table


def main():
    # 1. 把要插入的数据调整为dataframe格式
    dataframe = pd.DataFrame({
        "列1": [round(random.random(), 2) for _ in range(3)],
        "列2": [round(random.random(), 2) for _ in range(3)],
        "列3": [round(random.random(), 2) for _ in range(3)],
    })
    document = Document()

    # 2. 插入表格
    table = convert_df_to_table(document, dataframe, column_list=dataframe.columns.tolist())
    table = set_table_singleBoard(table)  # 表格添加边框
    base_paragraphs = document.add_paragraph("下面插入表格：")
    base_paragraphs._p.addnext(table._tbl)

    # 3. 保存修改后的结果
    document.save('测试_添加表格.docx')  # 保存后导出


if __name__ == '__main__':
    main()

上述代码会得到如下效果图：