Question

下面是一段代码片段，它根据服务器和本地之间的上次修改日期下载文件。

$ rvm osx-ssl-certs status all
Certificates for /etc/openssl/cert.pem: Up to date.
Certificates for /usr/local/etc/openssl/cert.pem: Up to date.
[~/couponler2 (production)]
$ rvm osx-ssl-certs update all
Updating certificates for /etc/openssl/cert.pem: Already up to date.
Updating certificates for /usr/local/etc/openssl/cert.pem: Already up to date.

当我在同一天修改文件时，我得到了正确的结果：

try:
    url = "https://10.10.10.10/version.ini"
    local_ini = ".//config/version.ini"
    filetime = (time.strftime('%a, %d %b %Y %X GMT', time.gmtime(os.path.getmtime(local_ini))))
    print("File Last Modified: {0}".format(filetime))
    r = requests.get(url,stream=True)
    meta = r.headers['last-modified']
    logging.info("Web  Last Modified: {0}".format(meta))
    if filetime < meta:
        print("Newer file found! Downloading...")
        if r != False:
            try:
                fileName = os.path.basename(urlparse.urlsplit(r.url)[2])
                with open(".//config/version.ini"e, 'wb') as f:
                     shutil.copyfileobj(r.raw,f)    
            finally:
                r.close()
    else:
        logging.info('No new version found. You got the latest file!') 

except requests.exceptions.RequestException as e:  
    logging.info(e)

但是当我修改文件时，有一天我得到了错误的结果：

File Last Modified: Thu, 12 Jan 2017 03:42:23 GMT
Web  Last Modified: Thu, 12 Jan 2017 03:44:22 GMT
Newer file found! Downloading...

为什么时间戳比较会给出错误的结果？

Answer 1

在您的示例中，meta是一个字符串，而不是time对象。如果你比较两个datetime个对象，你会有更好的运气：

if (dt.datetime.strptime(filetime, '%a, %d %b %Y %X GMT') < 
        dt.datetime.strptime(meta, '%a, %d %b %Y %X GMT')):

你需要：

 import datetime as dt

如果超过1天，则根据上次修改日期下载文件将失败

1 个答案: