Python根据URL地址下载文件并保存至对应目录的实现

引言

在编程中经常会遇到图片等数据集将图片等数据以URL形式存储在txt文档中，为便于后续的分析，需要将其下载下来，并按照文件夹分类存储。本文以Github中Alexander Kim提供的图片分类数据集为例，下载其提供的图片样本并分类保存

Python 3.6.5，Anaconda， VSCode

1. 下载数据集文件

建立项目文件夹，下载上述Github项目中的raw_data文件夹，并保存至项目目录中。

 2. 获取样本文件位置

编写get_doc_path.py，根据根目录位置，获取目录及其子目录所有数据集文件

import os

def get_file(root_path, all_files={}):
  '''
  递归函数，遍历该文档目录和子目录下的所有文件，获取其path
  '''
  files = os.listdir(root_path)
  for file in files:
    if not os.path.isdir(root_path + '/' + file):  # not a dir
      all_files[file] = root_path + '/' + file
    else: # is a dir
      get_file((root_path+'/'+file), all_files)
  return all_files

if __name__ == '__main__':
  path = './raw_data'
  print(get_file(path))

3. 下载文件

3.1 读取url列表并

for filename, path in paths.items():
    print('reading file: {}'.format(filename))
    with open(path, 'r') as f:
      lines = f.readlines()
      url_list = []
      for line in lines:
        url_list.append(line.strip('\n'))
      print(url_list)

3.2 创建文件夹

foldername = "./picture_get_by_url/pic_download/{}".format(filename.split('.')[0])
if not os.path.exists(folder_path):
    print("Selected folder not exist, try to create it.")
    os.makedirs(folder_path)

3.3 下载图片

def get_pic_by_url(folder_path, lists):
  if not os.path.exists(folder_path):
    print("Selected folder not exist, try to create it.")
    os.makedirs(folder_path)
  for url in lists:
    print("Try downloading file: {}".format(url))
    filename = url.split('/')[-1]
    filepath = folder_path + '/' + filename
    if os.path.exists(filepath):
      print("File have already exist. skip")
    else:
      try:
        urllib.request.urlretrieve(url, filename=filepath)
      except Exception as e:
        print("Error occurred when downloading file, error message:")
        print(e)

4. 完整源码

4.1 get_doc_path.py

import os

def get_file(root_path, all_files={}):
  '''
  递归函数，遍历该文档目录和子目录下的所有文件，获取其path
  '''
  files = os.listdir(root_path)
  for file in files:
    if not os.path.isdir(root_path + '/' + file):  # not a dir
      all_files[file] = root_path + '/' + file
    else: # is a dir
      get_file((root_path+'/'+file), all_files)
  return all_files

if __name__ == '__main__':
  path = './raw_data'
  print(get_file(path))

4.2 get_pic.py

import get_doc_path
import os
import urllib.request

def get_pic_by_url(folder_path, lists):
  if not os.path.exists(folder_path):
    print("Selected folder not exist, try to create it.")
    os.makedirs(folder_path)
  for url in lists:
    print("Try downloading file: {}".format(url))
    filename = url.split('/')[-1]
    filepath = folder_path + '/' + filename
    if os.path.exists(filepath):
      print("File have already exist. skip")
    else:
      try:
        urllib.request.urlretrieve(url, filename=filepath)
      except Exception as e:
        print("Error occurred when downloading file, error message:")
        print(e)

if __name__ == "__main__":
  root_path = './picture_get_by_url/raw_data'
  paths = get_doc_path.get_file(root_path)
  print(paths)
  for filename, path in paths.items():
    print('reading file: {}'.format(filename))
    with open(path, 'r') as f:
      lines = f.readlines()
      url_list = []
      for line in lines:
        url_list.append(line.strip('\n'))
      foldername = "./picture_get_by_url/pic_download/{}".format(filename.split('.')[0])
      get_pic_by_url(foldername, url_list)

4.3 运行结果

执行get_pic.py
当程序意外停止或再次执行时，程序会自动跳过文件夹中已下载的文件，继续下载未下载的内容

{‘urls_drawings.txt': ‘./picture_get_by_url/raw_data/drawings/urls_drawings.txt', ‘urls_hentai.txt': ‘./picture_get_by_url/raw_data/hentai/urls_hentai.txt', ‘urls_neutral.txt': ‘./picture_get_by_url/raw_data/neutral/urls_neutral.txt', ‘urls_porn.txt': ‘./picture_get_by_url/raw_data/porn/urls_porn.txt', ‘urls_sexy.txt': ‘./picture_get_by_url/raw_data/sexy/urls_sexy.txt'}
reading file: urls_drawings.txt
Try downloading file: http://41.media.tumblr.com/xxxxxx.jpg
Try downloading file: http://41.media.tumblr.com/xxxxxx.jpg
Try downloading file: http://ak1.polyvoreimg.com/cgi/img-thing/size/l/tid/xxxxxx.jpg
Error occurred when downloading file, error message:
HTTP Error 502: No data received from server or forwarder
Try downloading file: http://akicocotte.weblike.jp/gaugau/xxxxxx.jpg
Try downloading file: http://animewriter.files.wordpress.com/2009/01/nagisa-xxxxxx-xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg
Try downloading file: http://cdn.awwni.me/xxxxxx.jpg

后注：由于样本数据集内容的问题，上述地址以xxxxx代替具体地址，案例项目也已经失效，但是方法仍然可以借鉴

20.9.23更新：数据集地址：https://github.com/ZQ-Qi/nsfw_data_scrapper，单纯为了学习和实践本文代码的可以下载该数据集进行尝试

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