2020-06-30 11:47:19 +08:00
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## 制作报表
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2020-06-29 16:22:31 +08:00
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### 导出Excel报表
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报表就是用表格、图表等格式来动态显示数据，所以有人用这样的公式来描述报表：
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```
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报表 = 多样的格式 + 动态的数据
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```
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2020-07-14 00:04:30 +08:00
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有很多的三方库支持在Python程序中写Excel文件，包括[`xlwt`](<https://xlwt.readthedocs.io/en/latest/>)、[`xlwings`](<https://docs.xlwings.org/en/latest/quickstart.html>)、[`openpyxl`](<https://openpyxl.readthedocs.io/en/latest/>)、[`xlswriter`](<https://xlsxwriter.readthedocs.io/>)、[`pandas`](<http://pandas.pydata.org/>)等，其中的xlwt虽然只支持写xls格式的Excel文件，但在性能方面的表现还是不错的。下面我们就以`xlwt`为例，来演示如何在Django项目中导出Excel报表。
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安装`xlwt`。
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```Bash
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pip install xlwt
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```
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导出包含所有老师信息的Excel表格的视图函数。
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2020-06-29 16:22:31 +08:00
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```Python
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def export_teachers_excel(request):
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# 创建工作簿
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wb = xlwt.Workbook()
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# 添加工作表
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sheet = wb.add_sheet('老师信息表')
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# 查询所有老师的信息
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queryset = Teacher.objects.all()
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# 向Excel表单中写入表头
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colnames = ('姓名', '介绍', '好评数', '差评数', '学科')
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for index, name in enumerate(colnames):
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sheet.write(0, index, name)
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# 向单元格中写入老师的数据
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props = ('name', 'detail', 'good_count', 'bad_count', 'subject')
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for row, teacher in enumerate(queryset):
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for col, prop in enumerate(props):
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value = getattr(teacher, prop, '')
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if isinstance(value, Subject):
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value = value.name
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sheet.write(row + 1, col, value)
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# 保存Excel
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buffer = BytesIO()
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wb.save(buffer)
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# 将二进制数据写入响应的消息体中并设置MIME类型
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resp = HttpResponse(buffer.getvalue(), content_type='application/vnd.ms-excel')
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# 中文文件名需要处理成百分号编码
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filename = quote('老师.xls')
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# 通过响应头告知浏览器下载该文件以及对应的文件名
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resp['content-disposition'] = f'attachment; filename*=utf-8''{filename}'
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return resp
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```
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映射URL。
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```Python
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urlpatterns = [
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2020-07-14 00:04:30 +08:00
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2020-06-29 16:22:31 +08:00
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path('excel/', views.export_teachers_excel),
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2020-07-14 00:04:30 +08:00
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2020-06-29 16:22:31 +08:00
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]
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```
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2020-06-30 11:47:19 +08:00
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### 导出PDF报表
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2020-07-14 00:04:30 +08:00
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在Django项目中，如果需要导出PDF报表，可以借助三方库`reportlab`来生成PDF文件的内容，再将文件的二进制数据输出给浏览器并指定MIME类型为`application/pdf`，具体的代码如下所示。
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2020-06-30 11:47:19 +08:00
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```Python
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def export_pdf(request: HttpRequest) -> HttpResponse:
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buffer = io.BytesIO()
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pdf = canvas.Canvas(buffer)
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pdf.setFont("Helvetica", 80)
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pdf.setFillColorRGB(0.2, 0.5, 0.3)
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pdf.drawString(100, 550, 'hello, world!')
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pdf.showPage()
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pdf.save()
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resp = HttpResponse(buffer.getvalue(), content_type='application/pdf')
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resp['content-disposition'] = 'inline; filename="demo.pdf"'
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return resp
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```
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2020-07-14 00:04:30 +08:00
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关于如何用`reportlab`定制PDF报表的内容，可以参考reportlab的[官方文档](https://www.reportlab.com/docs/reportlab-userguide.pdf)。
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2020-06-30 11:47:19 +08:00
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2020-06-29 16:22:31 +08:00
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### 生成前端统计图表
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如果项目中需要生成前端统计图表，可以使用百度的[ECharts](<https://echarts.baidu.com/>)。具体的做法是后端通过提供数据接口返回统计图表所需的数据，前端使用ECharts来渲染出柱状图、折线图、饼图、散点图等图表。例如我们要生成一个统计所有老师好评数和差评数的报表，可以按照下面的方式来做。
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```Python
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def get_teachers_data(request):
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queryset = Teacher.objects.all()
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names = [teacher.name for teacher in queryset]
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good_counts = [teacher.good_count for teacher in queryset]
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bad_counts = [teacher.bad_count for teacher in queryset]
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return JsonResponse({'names': names, 'good': good_counts, 'bad': bad_counts})
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```
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映射URL。
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```Python
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urlpatterns = [
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path('teachers_data/', views.get_teachers_data),
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]
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```
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使用ECharts生成柱状图。
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```HTML
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<!DOCTYPE html>
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<html lang="en">
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<head>
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<meta charset="UTF-8">
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<title>老师评价统计</title>
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</head>
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<body>
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<div id="main" style="width: 600px; height: 400px"></div>
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<p>
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<a href="/">返回首页</a>
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</p>
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<script src="https://cdn.bootcss.com/echarts/4.2.1-rc1/echarts.min.js"></script>
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<script>
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var myChart = echarts.init(document.querySelector('#main'))
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fetch('/teachers_data/')
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.then(resp => resp.json())
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.then(json => {
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var option = {
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color: ['#f00', '#00f'],
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title: {
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text: '老师评价统计图'
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},
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tooltip: {},
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legend: {
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data:['好评', '差评']
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},
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xAxis: {
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data: json.names
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},
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yAxis: {},
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series: [
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{
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name: '好评',
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type: 'bar',
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data: json.good
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},
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{
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name: '差评',
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type: 'bar',
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data: json.bad
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}
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]
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}
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myChart.setOption(option)
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})
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</script>
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</body>
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</html>
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```
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运行效果如下图所示。
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