我目前正在成功使用python 2.7脚本,该脚本以递归方式遍历巨大的目录/文件路径,收集所有文件的路径,获取此类文件的mtime以及具有相同路径和名称但pdf的各个文件的mtime文件进行比较.我在python 2.7脚本中使用scandir.walk(),在python 3.7中使用os.walk(),最近已更新为也使用scandir算法(无其他stat()调用).
但是,脚本的python 3版本仍然明显慢一些!这不是由于算法的scandir / walk部分造成的,而是由于getmtime算法(但是,在python2和3中是相同的调用)或由于处理了巨大的列表(我们在说?).此列表中有500.000个条目).
任何想法可能导致此问题以及如何解决此问题?
#!/usr/bin/env python3
#
# Imports
#
import sys
import time
from datetime import datetime
import os
import re
#
# MAIN THREAD
#
if __name__ == '__main__':
source_dir = '/path_to_data/'
# Get file list
files_list = []
for root,directories,filenames in os.walk(source_dir):
# Filter for extension
for filename in filenames:
if (filename.lower().endswith(('.msg','.doc','.docx','.xls','.xlsx'))) and (not filename.lower().startswith('~')):
files_list.append(os.path.join(root,filename))
# Sort list
files_list.sort(reverse=True)
# For each file,the printing routine is performed (including necessity check)
all_documents_counter = len(files_list)
for docfile_abs in files_list:
print('n' + docfile_abs)
# Define files
filepathname_abs,file_extension = os.path.splitext(docfile_abs)
filepath_abs,filename = os.path.split(filepathname_abs)
# If the filename does not have the format # # # # # # # *.xxx (e.g. seven numbers),then it is checked whether it is referenced in the databse. If not,it is moved to a certain directory
if (re.match(r'[0-9][0-9][0-9][0-9][0-9][0-9][0-9](([Aa][0-9][0-9]?)?|(_[0-9][0-9]?)?|([Aa][0-9][0-9]?_[0-9][0-9]?)?)...?.?',filename + file_extension) is None):
if any(expression in docfile_abs for expression in ignore_subdirs):
pass
else:
print('Not in database')
# DOC
docfile_rel = docfile_abs.replace(source_dir,'')
# Check pdf
try:
pdf_file_abs = filepathname_abs + '.pdf'
pdf_file_timestamp = os.path.getmtime(pdf_file_abs)
check_pdf = True
except(FileNotFoundError):
check_pdf = False
# Check PDF
try:
PDF_file_abs = filepathname_abs + '.PDF'
PDF_file_timestamp = os.path.getmtime(PDF_file_abs)
check_PDF = True
except(FileNotFoundError):
check_PDF = False
# Check whether ther are lowercase or uppercase extension and decide what to do if there are none,just one or both present
if (check_pdf is True) and (check_PDF is False):
# Lower case case
pdf_extension = '.pdf'
pdffile_timestamp = pdf_file_timestamp
elif (check_pdf is False) and (check_PDF is True):
# Upper case case
pdf_extension = '.PDF'
pdffile_timestamp = PDF_file_timestamp
elif (check_pdf is False) and (check_PDF is False):
# None -> set timestampt to zero
pdf_extension = '.pdf'
pdffile_timestamp = 0
elif (check_pdf is True) and (check_PDF is True):
# Both are present,decide for the newest and move the other to a directory
if (pdf_file_timestamp < PDF_file_timestamp):
pdf_extension = '.PDF'
pdf_file_rel = pdf_file_abs.replace(source_dir,'')
pdffile_timestamp = PDF_file_timestamp
elif (PDF_file_timestamp < pdf_file_timestamp):
pdf_extension = '.pdf'
PDF_file_rel = PDF_file_abs.replace(source_dir,'')
pdffile_timestamp = pdf_file_timestamp
# Get timestamps of doc and pdf files
try:
docfile_timestamp = os.path.getmtime(docfile_abs)
except OSError:
docfile_timestamp = 0
# Enable this to force a certain period to be printed
DateBegin = time.mktime(time.strptime('01/02/2017',"%d/%m/%Y"))
DateEnd = time.mktime(time.strptime('01/03/2017',"%d/%m/%Y"))
# Compare stimestamps and print or not
if (pdffile_timestamp < docfile_timestamp) or (pdffile_timestamp == 0):
# Inform that there should be printed
print('tPDF should be printe.')
else:
# Inform that there was no need to print
print('tPDF is up to date.')
# Exit
sys.exit(0)
不知道是什么原因解释了差异,但是即使将os.walk增强为使用scandir,它也不会扩展到进一步的getmtime调用,后者将再次访问文件属性.
最终目标是根本不调用os.path.getmtime.
os.walk中的加速是关于不两次执行统计信息以了解对象是目录还是文件.但是内部的DirEntry对象(由scandir生成)从未公开,因此您无法重用它来检查文件时间.
如果您不需要重新启动,可以使用os.scandir完成:
for dir_entry in os.scandir(r"D:some_path"):
print(dir_entry.is_dir()) # test for directory
print(dir_entry.stat()) # returns stat object with date and all
循环内的那些调用以零成本完成,因为DirEntry对象已经缓存了此信息.
因此,要保存getmtime调用,您必须递归获取DirEntry对象.
没有本地方法,但是这里有示例,例如:How do I use os.scandir() to return DirEntry objects recursively on a directory tree?
这样,您的代码在python 2和python 3中将更快,因为每个对象只有1个stat调用,而不是2.
编辑:编辑以显示代码后,似乎您正在从其他条目中构建pdf名称,因此您不能依赖DirEntry结构来获取时间,甚至不能确定文件是否存在(即使您正在使用Windows,因为文件名不区分大小写,因此无需测试pdf和PDF).
最好的策略是建立一个包含相关时间和所有时间的大型文件数据库(使用字典),然后对其进行扫描.我已成功使用此方法在3500万个文件缓慢的网络驱动器上查找旧文件/大文件.在我的个人示例中,扫描文件一次,然后将结果转储到一个大的csv文件中(花了几个小时,获取了6Gb的csv数据),然后进行了进一步的后处理,加载了数据库并执行了各种任务(由于没有磁盘访问,因此速度更快参与)