Dash下载内存生成的文件，单击按钮：如何提供文件名？

Question

我通过pd.ExcelWriter和BytesIO为我的Python3.8仪表板应用程序中的点击事件生成了一个[[内存中 Excel文件。

一切正常。下载文件时，我收到此弹出消息，询问我是否要继续下载/打开生成的文件。但是，弹出消息显示了此字符串（我想是base64编码）字符串（或路径？），例如...ydaHdjhgk328AAAAnxsAA==，下载完成后，下载文件会获得一组（随机分配的？）字符作为文件名（例如ZySzsdn1.xlsx）。

如何调整它，以便显示并分配文件名给类似download.xlsx的文件？我的猜测是，这与base64编码的href有关。

生成excel文件的功能：

def write_product_file():
    output = BytesIO()
    writer = pd.ExcelWriter(output, engine="xlsxwriter")
    upload_df = pd.DataFrame()
    upload_df.to_excel(writer, index=False, sheet_name="sheet1")
    writer.save()
    return output

我的Dash应用程序中的按钮：
html.Div(
  id="select-upload-form",
  style={"width": "100%"},
  children=[
    dbc.Button(
      "Download the upload form",
      id="download-excel",
      color="secondary",
      external_link="true",
      target="",
      href="",
    ),
  ],
),

最后是我的回叫：
@app.callback(
    [
        Output("download-excel", "href"),
        Output("download-excel", "color"),
        Output("download-excel", "target"),
    ],
    [Input("download-excel", "n_clicks")],
)
def download_template_file(n_clicks):
    if n_clicks:
        excelfile = write_product_file()
        excelfile.seek(0)
        media_type = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"
        data = base64.b64encode(excelfile.read()).decode("utf-8")
        href_data = f"data:{media_type};base64,{data}"
        return href_data, "success", href_data,
    else:
        return None, "secondary", None

Answer 1

您可以使用破折号包中的Download组件，

pip install dash-extensions == 0.0.13

语法更简单，并且具有filename参数。这是一个小例子，
import io
import dash
import dash_html_components as html
import numpy as np
import pandas as pd

from dash.dependencies import Output, Input
from dash_extensions import Download

# Generate some example data.
data = np.column_stack((np.arange(10), np.arange(10) * 2))
df = pd.DataFrame(columns=["a column", "another column"], data=data)
# Create app.
app = dash.Dash(prevent_initial_callbacks=True)
app.layout = html.Div([html.Button("Download xslx", id="btn"), Download(id="download")])


@app.callback(Output("download", "data"), [Input("btn", "n_clicks")])
def generate_csv(n_nlicks):
    # Convert data to a string.
    bytes_io = io.BytesIO()
    xslx_writer = pd.ExcelWriter(bytes_io, engine="xlsxwriter")
    df.to_excel(xslx_writer, index=False, sheet_name="sheet1")
    xslx_writer.save()
    bytes = list(bytes_io.getvalue())
    # The output must follow this form for the download to work.
    return dict(filename="some_name.xslx", content=bytes, type="text/xslx")


if __name__ == '__main__':
    app.run_server()

免责声明：我是dash-extensions软件包的作者。