我正在尝试从python生成一个pdf文档。我希望它在输出文件中只打印一次，但它打印了四次 此脚本尝试生成pdf文件

它使用python的pollyreport库

from PollyReports import *
from reportlab.pdfgen.canvas import Canvas
    output = []
    with open('textfile.txt','r') as f:
        for line in f:
            if 'india' in line:
                output.append(line)
print output
rpt = Report(datasource = output, detailband = Band
            ([
                Element((10,10), ("Helvetica", 12), text=output[0]),
            ]))        

canvas = Canvas("lprep01.pdf")
rpt.generate(canvas)
canvas.save()