Question

我正在使用python破折号，并希望创建一个菜单/窗体列表，可以通过单击按钮来动态扩展和缩小菜单/窗体。添加新的表单/菜单应在页面上添加另一个相同的表单（表单/菜单列表）。

以下代码允许添加/删除包含多个仪表板核心组件的其他div，但是，每当我在下拉菜单之一中选择一个选项或在输入字段之一中输入任何内容时，我选择或输入的内容都会消失再次。

import dash
import dash_core_components as dcc
import dash_html_components as html

step = html.Div(
        children=[
            "Menu:",
            dcc.Dropdown(options=[{'label': v, 'value': v} for v in ['option1', 'option2', 'option3']]),
            dcc.Input(placeholder="Enter a value ...", type='text', value='')
        ])

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']
app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

div_list = [step]

app.layout = html.Div(
    children=[
        html.H1(children='Hello Dash'),
        html.Div(children=div_list, id='step_list'),
        html.Button('Add Step', id='add_step_button', n_clicks_timestamp='0'),
        html.Button('Remove Step', id='remove_step_button', n_clicks_timestamp='0')])


@app.callback(
    dash.dependencies.Output('step_list', 'children'),
    [dash.dependencies.Input('add_step_button', 'n_clicks_timestamp'),
     dash.dependencies.Input('remove_step_button', 'n_clicks_timestamp')],
    [dash.dependencies.State('step_list', 'children')])
def add_step(add_ts, remove_ts, div_list):
    add_ts = int(add_ts)
    remove_ts = int(remove_ts)
    if add_ts > 0 and add_ts > remove_ts:
        div_list += [step]
    if len(div_list) > 1 and remove_ts > add_ts:
        div_list = div_list[:-1]
    return div_list


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

有人可以向我解释我在做什么错吗？

非常感谢！

Answer 1

Dash组件需要指定id才能在回调后保存值。

此示例使用随机step生成id作为函数来解决此问题：

import dash
import dash_core_components as dcc
import dash_html_components as html
import numpy as np

def step():
     return html.Div(
        children=[
            "Menu:",
            dcc.Dropdown(options=[{'label': v, 'value': v} for v in ['option1', 'option2', 'option3']],id=str(np.random.randn())),
            dcc.Input(placeholder="Enter a value ...",id=str(np.random.randn()))
        ])

external_stylesheets = ['https://codepen.io/chriddyp/pen/bWLwgP.css']
app = dash.Dash(__name__, external_stylesheets=external_stylesheets)

app.layout = html.Div(
    children=[
        html.H1(children='Hello Dash'),
        html.Div(children=[step()], id='step_list'),
        html.Button('Add Step', id='add_step_button', n_clicks_timestamp='0'),
        html.Button('Remove Step', id='remove_step_button', n_clicks_timestamp='0')])

@app.callback(
    dash.dependencies.Output('step_list', 'children'),
    [dash.dependencies.Input('add_step_button', 'n_clicks_timestamp'),
     dash.dependencies.Input('remove_step_button', 'n_clicks_timestamp')],
    [dash.dependencies.State('step_list', 'children')])
def add_step(add_ts, remove_ts, div_list):
    add_ts = int(add_ts)
    remove_ts = int(remove_ts)
    if add_ts > 0 and add_ts > remove_ts:
        div_list += [step()]
    if len(div_list) > 1 and remove_ts > add_ts:
        div_list = div_list[:-1]
    return div_list

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

python dash核心组件的动态列表

1 个答案: