将解析的字符串值转换为浮点数

Question

将 Geopandas 与 Bokeh 结合使用，我正在可视化一个 GIS 数据集，该数据集也具有位置高程。高程值是 Double 类型，源自我正在加载的 Shapefile，例如'1382.770000'。

当向用户显示这些值时（例如，使用 HoverTool），它们以指数形式呈现，例如对于上面的例子 1.382e+3.

由于代码是面向用户/交互式的，我想以简化的浮点格式显示这些数字 - 这可以实现吗？

我试过了：

hover = HoverTool (tooltips = [('Elevation', float('@elev')])

然而这会带来一个ValueError: could not convert string to float: '@elev'

代码示例：

import pandas as pd
import geopandas as gpd
import json

import bokeh.io
from bokeh.io import output_notebook, show, output_file
from bokeh.plotting import figure, show
from bokeh.models import GeoJSONDataSource, HoverTool

# prevent Bokeh from savig sketch into file / opening in a new tab
bokeh.io.reset_output()
bokeh.io.output_notebook()

shapefile = 'data/USA Counties 20m/cb_2017_us_county_20m_with_cZone_USAF_coordinates_elevations.shp'

#Read shapefile using Geopandas
gdf = gpd.read_file(shapefile)[['CZONE', 'NAME', 'geometry','USAF','xcoord','ycoord','ELEV_IN_M']]

#Rename columns.
gdf.columns = ['cZone', 'Name', 'geometry','USAF','Long','Lat','elev']

#Reset index
gdf = gdf.reset_index(drop=True)

#Read data to json.
json_raw = json.loads(gdf.to_json())

#Convert to String like object.
json_data = json.dumps(json_raw)

#Input GeoJSON source that contains features for plotting.
geosource = GeoJSONDataSource(geojson = json_data)


#Add hover tools
hover = HoverTool(tooltips = [ ('Climate Zone','@cZone'),
                               ('County','@Name'),
                               ('USAF','@USAF'),
                               ('elev','@elev')])

#Create figure object.
p = figure(title = 'USA Climate Zone Map by County', plot_height = 450 , plot_width = 800, toolbar_location = "below")
p.add_tools(hover)

#Add patch renderer to figure. 
p.patches('xs','ys', source = geosource, 
          line_color = 'black', line_width = 0.25, fill_alpha = 1)

# Display figure & widget
show(p)

shapefile 可以到达here

Answer 1

您可以使用这样的工具提示格式（Bokeh v1.1.0）：

hover = HoverTool(tooltips = [ ('Climate Zone', '@cZone'),
                               ('County', '@Name'),
                               ('USAF', '@USAF'),
                               ('elev', '@{elev}{%0.3f}') ],
                  formatters = {'elev' : 'printf'} )