如何根据openpyxl中的值（负值或正值）更改图表的颜色？

Question

如何根据openpyxl中的值（负值或正值）更改图表的颜色？
  对我来说真的很难。

from openpyxl import Workbook
from openpyxl.styles import Border, Side, PatternFill, Font, GradientFill,Alignment, Color, numbers
from openpyxl.chart import BarChart, Reference

book = Workbook()
sheet = book.active
rows = [
['Number', 'Batch 1'],
['a', 40],
['b', -40],
['c', 50],
['d', -30],
['e', -25],
['f', 30],
]

for row in rows:
    sheet.append(row)

chart = BarChart()
chartCats = Reference(sheet, min_col=1, min_row=2, max_row=7)
chartData = Reference(sheet, min_col=2, min_row=1, max_col=2, max_row=7)
chart.add_data(chartData, titles_from_data = True)
chart.set_categories(chartCats)
chart.type = 'bar'
chart.style = 27
chart.height = 10
chart.width = 15
chart.legend = None
chart.x_axis.tickLblPos = "low"
chart.y_axis.number_format = '#,##0'
chart.y_axis.majorGridlines = None
sheet.add_chart(chart, 'A1')
book.save('test.xlsx')

上面的代码创建了标题为＆＃34; Batch1＆＃34;的图表。但我想要＆＃34; Batch2＆＃34;，其中负值和正值显示不同的颜色。

Answer 1

目前无法使用openpyxl完成此操作。按照https://www.extendoffice.com/documents/excel/2218-excel-chart-negative-values-different-color.html的说明，我在Excel中创建了一个图表，并对数据系列应用了差异格式。虽然openpyxl支持系列的invertIfNegative属性，但原始的OOXML规范不允许为数据系列添加其他颜色。这是使用原始规范的扩展来完成的。

Answer 2

这可以通过类实现

openpyxl.chart.marker.DataPoint()

和属性graphicProperties。这是基于您的代码的示例。我使用的OpenPyXl版本是2.5.1。

import openpyxl
from openpyxl import Workbook
from openpyxl.styles import Border, Side, PatternFill, Font, GradientFill,Alignment, Color, numbers
from openpyxl.chart import BarChart, Reference

book = Workbook()
sheet = book.active
rows = [
['Number', 'Batch 1'],
['a', 40],
['b', -40],
['c', 50],
['d', -30],
['e', -25],
['f', 30],
]

for row in rows:
    sheet.append(row)

chart = BarChart()
chartCats = Reference(sheet, min_col=1, min_row=2, max_row=7)
chartData = Reference(sheet, min_col=2, min_row=1, max_col=2, max_row=7)
chart.add_data(chartData, titles_from_data = True)
chart.set_categories(chartCats)
chart.type = 'bar'
chart.style = 27
chart.height = 10
chart.width = 15
chart.legend = None
chart.x_axis.tickLblPos = "low"
chart.y_axis.number_format = '#,##0'
chart.y_axis.majorGridlines = None

series = chart.series[0]
for i in range(len(rows)-1):
    if rows[i+1][1] < 0:
        pt = openpyxl.chart.marker.DataPoint(idx=i)
        pt.graphicalProperties.line.solidFill = 'A2B966'
        pt.graphicalProperties.solidFill = 'A2B966'
        series.dPt.append(pt)

sheet.add_chart(chart, 'A1')
book.save('test.xlsx')