Python模块进阶

模块路径

• 可以定义PYTHONPATH环境变量，定义自己的模块位置

[root@localhost day02] mkdir /opt/pylibs
[root@localhost day02] cp qsort.py /opt/pylibs
[root@localhost day02] export PYTHONPATH=/opt/pylibs
[root@localhost day02] cd /tmp/
[root@localhost tmp] python3
>>> import qsort

• python将目录当成特殊的模块，叫作包

[root@localhost day02]# mkdir pkgs
[root@localhost day02]# echo 'hi = "Hello World"' > pkgs/hello.py
[root@localhost day02]# cat pkgs/hello.py
hi = "Hello World"
[root@localhost day02]# python3
>>> import pkgs.hello
>>> pkgs.hello.hi
'Hello World'

hashlib

• 用于计算哈希值

>>> import hashlib
# 计算123456的md5值
>>> m = hashlib.md5(b'123456')
>>> m.hexdigest()
'e10adc3949ba59abbe56e057f20f883e'

# 当内容很多的时候，可以采用逐步更新的方式计算
>>> m1 = hashlib.md5()
>>> m1.update(b'12')
>>> m1.update(b'34')
>>> m1.update(b'56')
>>> m1.hexdigest()
'e10adc3949ba59abbe56e057f20f883e'

#模拟md5sum命令
import hashlib
import sys
def _hash(fn):
    has = hashlib.md5()
    with open(fn, 'rb') as fobj:
        while 1:
            con = fobj.read(4096)
            if not con:
                break
            has.update(con)
    return has.hexdigest()

if __name__ == '__main__':
    print('%s  %s' % (_hash(sys.argv[1]), sys.argv[1]))

tarfile

• 用于压缩、解压缩
• 同时支持gzip、bzip2格式

# 压缩
>>> import tarfile
>>> tar = tarfile.open('/tmp/mytest.tar.gz', 'w:gz')
>>> tar.add('/etc/hosts')
>>> tar.add('/etc/security')
>>> tar.close()

# 解压缩
>>> tar = tarfile.open('/tmp/mytest.tar.gz')
>>> tar.extractall(path='/var/tmp')  # 默认解压到当前目录
>>> tar.close()