ECharts Skill

Technology Stack

• pyecharts: Python wrapper for Apache ECharts
• Apache ECharts: JavaScript charting library
• Output: Self-contained HTML with embedded JS

Chart Types Reference

Bar Charts

from pyecharts.charts import Bar
from pyecharts import options as opts

chart = Bar()
chart.add_xaxis(labels)
chart.add_yaxis("Series Name", values)
chart.set_global_opts(
    title_opts=opts.TitleOpts(title="Chart Title"),
    tooltip_opts=opts.TooltipOpts(trigger="axis"),
    xaxis_opts=opts.AxisOpts(axislabel_opts=opts.LabelOpts(rotate=45)),
)

Line Charts

from pyecharts.charts import Line

chart = Line()
chart.add_xaxis(dates)
chart.add_yaxis("Actual", values, is_smooth=True)
chart.add_yaxis("7-Day MA", moving_avg_7, is_smooth=True, linestyle_opts=opts.LineStyleOpts(type_="dashed"))

Pie Charts

from pyecharts.charts import Pie

chart = Pie()
chart.add("", list(zip(labels, values)))
chart.set_global_opts(legend_opts=opts.LegendOpts(orient="vertical", pos_left="left"))

Heatmaps

from pyecharts.charts import HeatMap

chart = HeatMap()
chart.add_xaxis(x_labels)
chart.add_yaxis("", y_labels, value=[[x, y, val], ...])
chart.set_global_opts(
    visualmap_opts=opts.VisualMapOpts(min_=0, max_=max_val),
)

Scatter Plots (for anomalies)

from pyecharts.charts import Scatter

chart = Scatter()
chart.add_xaxis(dates)
chart.add_yaxis("Cost", costs, symbol_size=10)
# Add anomaly markers with different color/size

Critical: Browser Compatibility

Always convert to lists for JavaScript:

# CORRECT
chart.add_xaxis(df['column'].tolist())
chart.add_yaxis("Label", df['values'].tolist())

# WRONG - causes rendering issues
chart.add_xaxis(df['column'].values)  # numpy array
chart.add_xaxis(df['column'])  # pandas Series

Theme Options

Available themes in pyecharts:

• macarons (default) - Colorful, professional
• shine - Bright colors
• roma - Muted, elegant
• vintage - Retro feel
• dark - Dark background
• light - Light, minimal

Usage:

from pyecharts.globals import ThemeType
chart = Bar(init_opts=opts.InitOpts(theme=ThemeType.MACARONS))

HTML Report Structure

def generate_html_report(self, output_path: str, top_n: int = 10) -> str:
    # Create all charts
    charts = [
        self.create_cost_by_service_chart(top_n),
        self.create_cost_by_account_chart(),
        # ... more charts
    ]

    # Combine into page
    page = Page(layout=Page.SimplePageLayout)
    for chart in charts:
        page.add(chart)

    # Render to file
    page.render(output_path)
    return output_path

Formatting Numbers

# Currency formatting in tooltips
tooltip_opts=opts.TooltipOpts(
    trigger="axis",
    formatter="{b}: ${c:,.2f}"
)

# Axis label formatting
yaxis_opts=opts.AxisOpts(
    axislabel_opts=opts.LabelOpts(formatter="${value:,.0f}")
)

Common Issues & Solutions

Empty Charts

1. Check browser console for JS errors
2. Verify .tolist() on all data
3. Hard refresh (Ctrl+Shift+R)
4. Check data exists in HTML source

Chart Too Small

init_opts=opts.InitOpts(width="100%", height="400px")

Labels Overlapping

xaxis_opts=opts.AxisOpts(
    axislabel_opts=opts.LabelOpts(rotate=45, interval=0)
)

Legend Too Long

legend_opts=opts.LegendOpts(
    type_="scroll",
    orient="horizontal",
    pos_bottom="0%"
)

Design Guidelines

Create ECharts visualizations with these requirements:

1. Responsive Layout

Use 100% width and height (not fixed px):

init_opts=opts.InitOpts(width="100%", height="400px")

2. Modern Color Palette

Use a professional scheme:

colors = ['#5470c6', '#91cc75', '#fac858', '#ee6666', '#73c0de']

3. Clean Styling

• White/transparent background
• Subtle grid lines (opacity 0.1)
• Proper padding:

grid_opts=opts.GridOpts(pos_left="60px", pos_right="40px", pos_top="60px", pos_bottom="40px")

4. Typography

• Title: 16-18px, bold, dark color
• Axis labels: 12px

title_opts=opts.TitleOpts(
    title="Chart Title",
    title_textstyle_opts=opts.TextStyleOpts(font_size=18, font_weight="bold", color="#333")
)

5. Interactions

Enable tooltip with shadow and add toolbox:

tooltip_opts=opts.TooltipOpts(trigger="axis", axis_pointer_type="shadow")
toolbox_opts=opts.ToolboxOpts(
    feature=opts.ToolBoxFeatureOpts(
        save_as_image=opts.ToolBoxFeatureSaveAsImageOpts(),
        data_zoom=opts.ToolBoxFeatureDataZoomOpts()
    )
)

6. Animation

Smooth entrance animation (enabled by default in pyecharts)

Raw HTML Structure (for non-pyecharts)

<div id="chart" style="width:100%;height:100%;min-height:400px;"></div>
<script>
var chart = echarts.init(document.getElementById('chart'));
chart.setOption({
  color: ['#5470c6', '#91cc75', '#fac858', '#ee6666', '#73c0de'],
  grid: { left: 60, right: 40, top: 60, bottom: 40 },
  tooltip: { trigger: 'axis', axisPointer: { type: 'shadow' } },
  toolbox: { feature: { saveAsImage: {}, dataZoom: {} } },
  // ... chart-specific options
});
window.addEventListener('resize', () => chart.resize());
</script>

Quick Reference Checklist

• Responsive (100% width/height, min-height 400px)
• Modern colors (#5470c6, #91cc75, #fac858, #ee6666, #73c0de)
• Proper grid padding and subtle grid lines
• Tooltip, toolbox, and resize handler included

Testing Visualizations

# Test chart creation
uv run pytest tests/test_visualizer.py -v

# Regenerate example report
uv run pytest tests/test_examples.py -v -s

# View in browser
open examples/example_report.html