单击按钮时 Dash 下载内存中生成的文件：如何给出文件名？

Question

我生成内存通过Excel文件pd.ExcelWriter，并BytesIO在我的Python3.8仪表应用点击事件。

一切正常。当我下载我的文件时，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，弹出消息显示了这个（我猜是base64编码的）字符串（或路径？），例如...ydaHdjhgk328AAAAnxsAA==，下载下载后会获得一组（随机分配的？）字符集作为文件名（例如ZySzsdn1.xlsx）。

我该如何调整它才能显示文件名并将其分配给类似的东西download.xlsx？我的猜测是这与base64编码的href.

生成excel文件的函数：

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="",
    ),
  ],
),

最后我的回调：

@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Downloaddash-extensions 包中的组件，

pip install dash-extensions == 0.0.18

语法更简单，它有一个filename参数。这是一个小例子，

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
from dash_extensions.snippets import send_bytes

# 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 xlsx", id="btn"), Download(id="download")])


@app.callback(Output("download", "data"), [Input("btn", "n_clicks")])
def generate_xlsx(n_nlicks):

    def to_xlsx(bytes_io):
        xslx_writer = pd.ExcelWriter(bytes_io, engine="xlsxwriter")
        df.to_excel(xslx_writer, index=False, sheet_name="sheet1")
        xslx_writer.save()

    return send_bytes(to_xlsx, "some_name.xlsx")


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

免责声明：我是 dash-extensions 包的作者。