问题
I generate an in-memory Excel file via pd.ExcelWriter
and BytesIO
for a click event in my Python3.8 dash app.
Everything works as it should be. When I download my file I get this popup message asking me if I would like to continue to download/open the generated file. However, the popup message shows this (I guess base64
encoded) string (or path?), e.g. ...ydaHdjhgk328AAAAnxsAA==
and after downloading the download gets a (randomly assigned?) set of characters as the filename (e.g. ZySzsdn1.xlsx
).
How can I adjust this so it would display and assign the filename to something like download.xlsx
? My guess is that is has something to do with the base64
encoded href
.
The function to generate the excel file:
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
The button in my Dash application:
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="",
),
],
),
And finally my callback:
@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
回答1:
You could use the Download
component from the dash-extensions package,
pip install dash-extensions == 0.0.18
The syntax is simpler, and it has a filename
argument. Here is a small example,
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()
Disclaimer: I am the author of the dash-extensions package.
来源:https://stackoverflow.com/questions/62082946/dash-download-in-memory-generated-file-on-button-click-how-to-give-filename