gzip — 读写 GNU zip 压缩文件

写压缩文件

# gzip_write.py
import gzip
import io
import os

outfilename = 'example.txt.gz'
with gzip.open(outfilename, 'wb') as output:
    with io.TextIOWrapper(output, encoding='utf-8') as enc:
        enc.write('Contents of the example file go here.\n')

print(outfilename, 'contains', os.stat(outfilename).st_size,
      'bytes')
os.system('file -b --mime {}'.format(outfilename))

# gzip_compresslevel.py
import gzip
import io
import os
import hashlib


def get_hash(data):
    return hashlib.md5(data).hexdigest()


data = open('lorem.txt', 'r').read() * 1024
cksum = get_hash(data.encode('utf-8'))


print('Level  Size        Checksum')
print('-----  ----------  ---------------------------------')
print('data   {:>10}  {}'.format(len(data), cksum))

for i in range(0, 10):
    filename = 'compress-level-{}.gz'.format(i)
    with gzip.open(filename, 'wb', compresslevel=i) as output:
        with io.TextIOWrapper(output, encoding='utf-8') as enc:
            enc.write(data)
    size = os.stat(filename).st_size
    cksum = get_hash(open(filename, 'rb').read())
    print('{:>5d}  {:>10d}  {}'.format(i, size, cksum))

# gzip_writelines.py
import gzip
import io
import itertools
import os

with gzip.open('example_lines.txt.gz', 'wb') as output:
    with io.TextIOWrapper(output, encoding='utf-8') as enc:
        enc.writelines(
            itertools.repeat('The same line, over and over.\n',
                             10)
        )

os.system('gzcat example_lines.txt.gz')

读压缩数据

# gzip_read.py
import gzip
import io

with gzip.open('example.txt.gz', 'rb') as input_file:
    with io.TextIOWrapper(input_file, encoding='utf-8') as dec:
        print(dec.read())

# gzip_seek.py
import gzip

with gzip.open('example.txt.gz', 'rb') as input_file:
    print('Entire file:')
    all_data = input_file.read()
    print(all_data)

    expected = all_data[5:15]

    # rewind to beginning
    input_file.seek(0)

    # move ahead 5 bytes
    input_file.seek(5)
    print('Starting at position 5 for 10 bytes:')
    partial = input_file.read(10)
    print(partial)

    print()
    print(expected == partial)

处理流

# gzip_BytesIO.py
import gzip
from io import BytesIO
import binascii

uncompressed_data = b'The same line, over and over.\n' * 10
print('UNCOMPRESSED:', len(uncompressed_data))
print(uncompressed_data)

buf = BytesIO()
with gzip.GzipFile(mode='wb', fileobj=buf) as f:
    f.write(uncompressed_data)

compressed_data = buf.getvalue()
print('COMPRESSED:', len(compressed_data))
print(binascii.hexlify(compressed_data))

inbuffer = BytesIO(compressed_data)
with gzip.GzipFile(mode='rb', fileobj=inbuffer) as f:
    reread_data = f.read(len(uncompressed_data))

print('\nREREAD:', len(reread_data))
print(reread_data)