使用Aspose.Slides for Python API，通过获取LineChart数据点对应的Series对象，再获取SeriesDataPoint，最后设置LabelFormat属性实现数据标签格式控制。以下是示例代码：

from asposeslides import Presentation
from asposeslides.charts import ChartType
from asposeslides.charts import LineChart
from asposeslides.charts import ChartDataPointType
from asposeslides.charts import ChartDataPoint
from asposeslides.charts import ChartSeries
from asposeslides.charts import LabelFormat

# 加载演示文稿
pres = Presentation("presentation.pptx")
# 获取第一个幻灯片
slide = pres.slides[0]
# 插入一个空白的折线图
chart_type = ChartType.Line
chart = slide.shapes.add_chart(chart_type, 0, 0, 500, 300, True)
line_chart = chart.chart_data.chart
# 添加一个数据系列
series = line_chart.series.add("销售额")
# 添加数据点
data_points = series.data_points
data_points.add_data_point(ChartDataPointType.DataPointNumeric, 50)
data_points.add_data_point(ChartDataPointType.DataPointNumeric, 30)
data_points.add_data_point(ChartDataPointType.DataPointNumeric, 70)
data_points.add_data_point(ChartDataPointType.DataPointNumeric, 40)
data_points.add_data_point(ChartDataPointType.DataPointNumeric, 60)
# 获取每个数据点对象
for point in data_points:
    # 获取每个数据点对应的Series对象
    series = point.series
    # 获取SeriesDataPoint对象
    data_point = series.data_points[point.index]
    # 设置数据标签格式控制
    label_format = data_point.label.format
    label_format.text_format.portion_format.font_height = 12 # 字体大小
    label_format.number_format = "$#.00" # 数字格式

# 保存演示文稿
pres.save("presentation.pptx")

其中，通过访问LineChart对象上的Series对象，再获取SeriesDataPoint对象，最后通过设置LabelFormat属性，实现LineChart数据标签的格式控制。