python read文件内容的iter方式

遍历file的方式

iter(lambda: f.read(4096), "")
等价与
while True:
    data = f.read(4096)
    if not data:
        break
    hash_md5.updata(data)

# 生成md5
def get_file_md5(fname):
    hash_md5 = hashlib.md5()
    with open(fname, "rb") as f:
        print type(f)
        for chunk in iter(lambda: f.read(4096), ""):
            hash_md5.update(chunk)

    return base64.b64encode(hash_md5.digest())