带有bokeh vbar图的分类y轴和日期时间x轴

我想使用bokeh绘制vbar图，其中x轴为日期时间，y轴为分类值.

I want to draw a vbar plot using bokeh, where x-axis takes datetime and y-axis takes categorical values.

最初，我尝试如下绘制圆形图:

Initially I tried circle plot as follows:

import pandas as pd
from datetime import datetime
from dateutil.parser import parse    
from bokeh.plotting import figure, show, output_notebook    
from bokeh.models.ranges import FactorRange

x = pd.Series(['2017/1/1', '2017/1/2', '2017/1/3', '2017/1/4']).map(lambda x: parse(x))
y = ["a", "b", "c", "a"]

p = figure(x_axis_type='datetime', y_range=list(set(y)), plot_width=400, plot_height=200)
p.circle(x, y, size=10, line_color="blue", line_width=1)
show(p)

看起来不错，除了它不是条形.

It looks good except for the fact that it is not in bar form.

接下来，我尝试了以下代码，但未显示图:

Next, I tried the following code but no plots are displayed:

x = pd.Series(['2017/1/1', '2017/1/2', '2017/1/3', '2017/1/4']).map(lambda x: parse(x))
y = ["a", "b", "c", "a"]

p = figure(x_axis_type='datetime', y_range=list(set(y)), plot_width=400, plot_height=200)
p.vbar(x=x, bottom=0, top=y, width=0.1, color="blue")

show(p)