python - 如何使用 ipywidgets 创建动态依赖下拉菜单？

Question

我创建了一个带有两个下拉菜单的表单:

我的目标是使一个下拉列表依赖于另一个下拉列表。

This picture illustrates my goal and the current situation.

下面的示例代码可以在 Google Colab 或 Jupyter Notebook 中运行来复制当前情况。

#@title 
import ipywidgets as widgets
from ipywidgets import HBox, Label
from ipywidgets import Layout, Button, Box, FloatText, Textarea, Dropdown, Label, IntSlider
import time
import pandas as pd

#Create DF
df = df = pd.DataFrame(columns = ['Dropdown_column', 'Float_column'])
df

# Layout
form_item_layout = Layout(
    display='flex',
    flex_flow='row',
    justify_content='space-between',
)


button_item_layout = Layout(
    display='flex',
    flex_flow='row',
    justify_content='center',
    padding = '5%'
)


# Independent dropdown item

drop_down_input = 'Dropdown_input_1'

drop_down = widgets.Dropdown(options=('Dropdown_input_1', 'Dropdown_input_2'))

def dropdown_handler(change):
    global drop_down_input
    print('\r','Dropdown: ' + str(change.new),end='')
    drop_down_input = change.new

drop_down.observe(dropdown_handler, names='value')


# Dependent drop down

# Dependent drop down elements

dependent_drop_down_elements = {}
dependent_drop_down_elements['Dropdown_input_1'] = ['A', 'B']
dependent_drop_down_elements['Dropdown_input_2'] = ['C', 'D', 'E'] 

# Define dependent drop down

dependent_drop_down = widgets.Dropdown(options=(dependent_drop_down_elements['Dropdown_input_1']))

def dropdown_handler(change):
    global drop_down_input
    print('\r','Dropdown: ' + str(change.new),end='')
    drop_down_input = change.new  
drop_down.observe(dropdown_handler, names='value')



# Button

button = widgets.Button(description='Add row to dataframe')
out = widgets.Output()
def on_button_clicked(b):
    global df
    button.description = 'Row added'
    time.sleep(1)
    with out:
      new_row = {'Dropdown_column': drop_down_input, 'Float_column': float_input}
      df = df.append(new_row, ignore_index=True)
      button.description = 'Add row to dataframe'
      out.clear_output()  
      display(df)
button.on_click(on_button_clicked)

# Form items

form_items = [         
    Box([Label(value='Independent dropdown'),
         drop_down], layout=form_item_layout),
    Box([Label(value='Dependent dropdown'),
         dependent_drop_down], layout=form_item_layout)
         ]

form = Box(form_items, layout=Layout(
    display='flex',
    flex_flow='column',
    border='solid 1px',
    align_items='stretch',
    width='30%',
    padding = '1%'
))
display(form)
display(out)

这可能吗？如果是这样，你能解释一下怎么做吗？

Answer 1

您可以通过在 dropdown_handler 函数中设置 if 语句来执行此操作，该语句检查独立下拉列表中选择的值是否为 Dropdown_input_1 或Dropdown_input2。仍然在 dropdown_handler 中，您可以将 options 参数相应地修改为 dependent_drop_down_elements['Dropdown_input_1'] 或 dependent_drop_down_elements['Dropdown_input_2 ']。

参见下面的代码:

import ipywidgets as widgets
from ipywidgets import HBox, Label
from ipywidgets import Layout, Button, Box, FloatText, Textarea, Dropdown, Label, IntSlider
import time
import pandas as pd

#Create DF
df = df = pd.DataFrame(columns = ['Dropdown_column', 'Float_column'])
df

# Layout
form_item_layout = Layout(
    display='flex',
    flex_flow='row',
    justify_content='space-between',
)


button_item_layout = Layout(
    display='flex',
    flex_flow='row',
    justify_content='center',
    padding = '5%'
)


# Independent dropdown item

drop_down_input = 'Dropdown_input_1'
drop_down = widgets.Dropdown(options=('Dropdown_input_1', 'Dropdown_input_2'))


# Dependent drop down
# Dependent drop down elements
dependent_drop_down_elements = {}
dependent_drop_down_elements['Dropdown_input_1'] = ['A', 'B']
dependent_drop_down_elements['Dropdown_input_2'] = ['C', 'D', 'E'] 

# Define dependent drop down

dependent_drop_down = widgets.Dropdown(options=(dependent_drop_down_elements['Dropdown_input_1']))

def dropdown_handler(change):
    global drop_down_input
    print('\r','Dropdown: ' + str(change.new),end='')
    drop_down_input = change.new
    #If statement checking on dropdown value and changing options of the dependent dropdown accordingly
    if change.new=='Dropdown_input_2':
       dependent_drop_down.options=dependent_drop_down_elements['Dropdown_input_2']
    elif change.new=='Dropdown_input_1':
        dependent_drop_down.options=dependent_drop_down_elements['Dropdown_input_1']
drop_down.observe(dropdown_handler, names='value')

# Button

button = widgets.Button(description='Add row to dataframe')
out = widgets.Output()
def on_button_clicked(b):
    global df
    button.description = 'Row added'
    time.sleep(1)
    with out:
      new_row = {'Dropdown_column': drop_down_input, 'Float_column': float_input}
      df = df.append(new_row, ignore_index=True)
      button.description = 'Add row to dataframe'
      out.clear_output()  
      display(df)
button.on_click(on_button_clicked)

# Form items

form_items = [         
    Box([Label(value='Independent dropdown'),
         drop_down], layout=form_item_layout),
    Box([Label(value='Dependent dropdown'),
         dependent_drop_down], layout=form_item_layout)
         ]

form = Box(form_items, layout=Layout(
    display='flex',
    flex_flow='column',
    border='solid 1px',
    align_items='stretch',
    width='30%',
    padding = '1%'
))
display(form)
display(out)

例如，当您在第一个小部件上选择 Dropdown_input_2 时，输出如下所示: