python - 组合两个for循环以提高效率

Question

我通过循环 csv 文件来制作一堆图表，然后根据 groupby 制作多个图表。代码如下:

import pandas as pd   
import matplotlib.pyplot as plt
from matplotlib.backends.backend_pdf import PdfPages


frame=pd.read_csv('C:\\')

pdf_files = {}
for group_name, group in frame.groupby(['Allotment','Year','Month','Day']):
    allotment,year,month,day = group_name
    if month not in pdf_files:
        pdf_files[allotment,month] = PdfPages(r'F:\Sheyenne\Statistics\IDL_stats\Allotment_histos\Month\SWIR32' + '_' + allotment + '_'+ month + '.pdf') 
    plot=group.plot(x='Percent', y='SWIR32', title=str(group_name)).get_figure()
    pdf_files[allotment,month].savefig(plot)
    plt.close(plot)

for key in pdf_files:
    pdf_files[key].close()

print "Done"  

但这返回一个错误，指出打开的文件太多。我认为如果我可以将两个 for 循环合并为一个，这可能会解决这个问题，但我不确定如何做到这一点。

Answer 1

出于任何原因，您不能首先对 ['allotment', 'month'] 进行分组，然后每个循环将只是一个 pdf 文件(并且可能更好地将 与 PdfPages(. ..) 作为 pdf_file:)

basename = r'F:\Sheyenne\Statistics\IDL_stats\Allotment_histos\Month\SWIR32'
for file_name, file in frame.groupby(['Allotment','Month']):
    allotment, month = file_name
    with PdfPages('{}_{}_{}.pdf'.format(basename, allotment, month)) as pdf_file:
        for group_name, group in file.groupby(['Allotment','Month','Year', 'Day']):
            plot = group.plot(x='Percent', y='SWIR32', title=str(group_name)).get_figure()
            pdf_file.savefig(plot)
            plt.close(plot)