Python模塊進階

模塊路徑

• 可以定義PYTHONPATH環境變量，定義自己的模塊位置

[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將目錄當成特殊的模塊，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

• 用於計算哈希值

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

# 當內容很多的時候，可以採用逐步更新的方式計算
>>> m1 = hashlib.md5()
>>> m1.update(b'12')
>>> m1.update(b'34')
>>> m1.update(b'56')
>>> m1.hexdigest()
'e10adc3949ba59abbe56e057f20f883e'

#模擬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

• 用於壓縮、解壓縮
• 同時支持gzip、bzip2格式

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

# 解壓縮
>>> tar = tarfile.open('/tmp/mytest.tar.gz')
>>> tar.extractall(path='/var/tmp')  # 默認解壓到當前目錄
>>> tar.close()