Python 代码片段整理

1、numpy.random.shuffle(x)

 import numpy as np

 x = []
 for i in range(10):
     x.append(i)

 print(x)
 np.random.shuffle(x)
 print (x)

2、python 下载文件 urllib

 import urllib.request
 import os
 import sys
 import tarfile

 def download_and_uncompress_tarball(tarball_url, dataset_dir):
   """Downloads the `tarball_url` and uncompresses it locally.
   Args:
     tarball_url: The URL of a tarball file.
     dataset_dir: The directory where the temporary files are stored.
   """
   filename = tarball_url.split('/')[-1]
   filepath = os.path.join(dataset_dir, filename)

   def _progress(count, block_size, total_size):
     sys.stdout.write('\r>> Downloading %s %.1f%%' % (
         filename, float(count * block_size) / float(total_size) * 100.0))
     sys.stdout.flush()
   filepath, _ = urllib.request.urlretrieve(tarball_url, filepath, _progress)
   print()
   statinfo = os.stat(filepath)
   print('Successfully downloaded', filename, statinfo.st_size, 'bytes.')
   tarfile.open(filepath, 'r:gz').extractall(dataset_dir)

 DATA_URL = 'http://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz'
 DATA_DIR = 'data'

 download_and_uncompress_tarball(DATA_URL, DATA_DIR)

a).使用 urllib.request.urlretrieve下载

b).内嵌入了一个 回调函数 _progress，显示其进度

c).使用 tar.file.open 进行解压