常用技巧

控制函数的参数个数

import hashlib
import sys

def main():
    if len(sys.argv) != 2:
        sys.exit('Usage: %s file' % sys.argv[0])

    filename = sys.argv[1]
    m = hashlib.md5()
    with open(filename, 'rb') as fp:
        while True:
            blk = fp.read(4096) # 4KB per block
            if not blk: break
            m.update(blk)
    print m.hexdigest(), filename

if __name__ == '__main__':
    main()

控制多个异常exceptions

def is_uuid_like(val):
    """Returns validation of a value as a UUID.

    For our purposes, a UUID is a canonical form string:
    aaaaaaaa-aaaa-aaaa-aaaa-aaaaaaaaaaaa
    """
    try:
        return str(uuid.UUID(val)) == val
    except (TypeError, ValueError, AttributeError):
        return False