blocks|key|1815057|text|你可以尝试下载数据，如果连接失败，你就会知道连接的某些东西不好。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1815058|基本上你不能检查电脑是否连上了互联网。失败的原因可能有很多，例如错误的DNS配置、防火墙、NAT。因此，即使你做了一些测试，你也不能保证在你尝试之前，你能连接到你的API。|1815059|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

You can just try to download data, and if connection fail you will know that somethings with connection isn't fine.

Basically you can't check if computer is connected to internet. There can be many reasons for failure, like wrong DNS configuration, firewalls, NAT. So even if you make some tests, you can't have guaranteed that you will have connection with your API until you try.

blocks|key|3099062|text|也许你可以使用这样的东西：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3099063|import+urllib2

def+internet_on():
++++try:
++++++++urllib2.urlopen('http://216.58.192.142',+timeout=1)
++++++++return+True
++++except+urllib2.URLError+as+err:+
++++++++return+False|code-block|syntax|javascript|3099064|目前，216.58.192.142是google.com的IP地址之一。将http://216.58.192.142更改为任何可以快速响应的站点。|offset|length|style|CODE|3099065|此固定IP不会永远映射到google.com。所以这段代码并不健壮--它需要不断的维护才能使其正常工作。|3099066|上面代码使用固定IP地址而不是完全限定域名(+FQDN+)的原因是因为FQDN需要DNS查找。当机器没有工作的互联网连接时，DNS查找本身可能会阻止对urllib_request.urlopen的调用超过一秒钟。感谢@rzetterberg指出这一点。|3099067|3099068|如果上面的固定IP地址不起作用，您可以通过运行以下命令查找google.com+(在unix上)的当前IP地址|3099069|%25+dig+google.com++%2Btrace+
...
google.com.+++++300+IN++A+++216.58.192.142|3099070|entityMap^0|0|0|11|L|0|0|23|M|0|0|0|0^^$0|@$1|2|3|4|5|6|7|X|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Z|8|@$I|10|J|11|K|L]]|9|@]|A|$]]|$1|M|3|N|5|6|7|12|8|@]|9|@]|A|$]]|$1|O|3|P|5|6|7|13|8|@$I|14|J|15|K|L]]|9|@]|A|$]]|$1|Q|3|-4|5|6|7|16|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|17|8|@]|9|@]|A|$]]|$1|T|3|U|5|D|7|18|8|@]|9|@]|A|$E|F]]|$1|V|3|-4|5|6|7|19|8|@]|9|@]|A|$]]]|W|$]]

Perhaps you could use something like this:

<pre><code>import urllib2

def internet_on():
 try:
 urllib2.urlopen('http://216.58.192.142', timeout=1)
 return True
 except urllib2.URLError as err: 
 return False
</code></pre>

Currently, 216.58.192.142 is one of the IP addresses for google.com. Change <code>http://216.58.192.142</code> to whatever site can be expected to respond quickly. 

This fixed IP will not map to google.com forever. So this code is
not robust -- it will need constant maintenance to keep it working. 

The reason why the code above uses a fixed IP address instead of fully qualified domain name (FQDN) is because a FQDN would require a DNS lookup. When the machine does not have a working internet connection, the DNS lookup itself may block the call to <code>urllib_request.urlopen</code> for more than a second. Thanks to @rzetterberg for pointing this out.

<hr>

If the fixed IP address above is not working, you can find a current IP address for google.com (on unix) by running

<pre><code>% dig google.com +trace 
...
google.com. 300 IN A 216.58.192.142
</code></pre>

blocks|key|4509835|text|无论如何，请尝试您正在尝试执行的操作。如果失败，python应该抛出一个异常让你知道。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4509836|先尝试一些微不足道的操作来检测连接将引入竞争条件。如果互联网连接在您测试时有效，但在您需要进行实际工作之前就中断了，该怎么办？|4509837|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Try the operation you were attempting to do anyway. If it fails python should throw you an exception to let you know.

To try some trivial operation first to detect a connection will be introducing a race condition. What if the internet connection is valid when you test but goes down before you need to do actual work?

blocks|key|4509874|text|更新一下unutbu在Python3.2中所说的新代码|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4509875|def+check_connectivity(reference):
++++try:
++++++++urllib.request.urlopen(reference,+timeout=1)
++++++++return+True
++++except+urllib.request.URLError:
++++++++return+False|code-block|syntax|javascript|4509876|并且，只需注意，这里的输入(引用)是您想要检查的url+:我建议选择与您居住的地方连接最快的url+--例如，我住在韩国，所以我可能会将引用设置为http://www.naver.com。|offset|length|4509877|entityMap|0|LINK|mutability|MUTABLE|url|http://www.naver.com/^0|0|0|21|K|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@$I|V|J|W|1|X]]|A|$]]|$1|K|3|-4|5|6|7|Y|8|@]|9|@]|A|$]]]|L|$M|$5|N|O|P|A|$Q|R]]]]

Just to update what unutbu said for new code in Python 3.2

<pre><code>def check_connectivity(reference):
 try:
 urllib.request.urlopen(reference, timeout=1)
 return True
 except urllib.request.URLError:
 return False
</code></pre>

And, just to note, the input here (reference) is the url that you want to check: I suggest choosing something that connects fast where you live -- i.e. I live in South Korea, so I would probably set reference to <a href="http://www.naver.com" rel="noreferrer">http://www.naver.com</a>.

blocks|key|4509908|text|作为ubutnu/Kevin+C+answers的替代，我使用requests包，如下所示：|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4509909|import+requests

def+connected_to_internet(url='http://www.google.com/',+timeout=5):
++++try:
++++++++_+=+requests.head(url,+timeout=timeout)
++++++++return+True
++++except+requests.ConnectionError:
++++++++print("No+internet+connection+available.")
++++return+False|code-block|syntax|javascript|4509910|奖励:这可以扩展到这个功能，可以ping一个网站。|4509911|def+web_site_online(url='http://www.google.com/',+timeout=5):
++++try:
++++++++req+=+requests.head(url,+timeout=timeout)
++++++++#+HTTP+errors+are+not+raised+by+default,+this+statement+does+that
++++++++req.raise_for_status()
++++++++return+True
++++except+requests.HTTPError+as+e:
++++++++print("Checking+internet+connection+failed,+status+code+{0}.".format(
++++++++e.response.status_code))
++++except+requests.ConnectionError:
++++++++print("No+internet+connection+available.")
++++return+False|4509912|entityMap^0|V|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

As an alternative to ubutnu's/Kevin C answers, I use the <code>requests</code> package like this:
<pre><code>import requests

def connected_to_internet(url='http://www.google.com/', timeout=5):
 try:
 _ = requests.head(url, timeout=timeout)
 return True
 except requests.ConnectionError:
 print(&quot;No internet connection available.&quot;)
 return False
</code></pre>
Bonus: this can be extended to this function that pings a website.
<pre><code>def web_site_online(url='http://www.google.com/', timeout=5):
 try:
 req = requests.head(url, timeout=timeout)
 # HTTP errors are not raised by default, this statement does that
 req.raise_for_status()
 return True
 except requests.HTTPError as e:
 print(&quot;Checking internet connection failed, status code {0}.&quot;.format(
 e.response.status_code))
 except requests.ConnectionError:
 print(&quot;No internet connection available.&quot;)
 return False
</code></pre>

blocks|key|1815141|text|只做一个HEAD请求会更快，这样就不会获取HTML。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1815142|此外，我相信google会更喜欢这种方式:)|1815143|try:
++++import+httplib++#+python+<+3.0
except:
++++import+http.client+as+httplib


def+have_internet():
++++conn+=+httplib.HTTPSConnection("8.8.8.8",+timeout=5)
++++try:
++++++++conn.request("HEAD",+"/")
++++++++return+True
++++except+Exception:
++++++++return+False
++++finally:
++++++++conn.close()|code-block|syntax|javascript|1815144|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|L|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|M|8|@]|9|@]|A|$G|H]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

It will be faster to just make a HEAD request so no HTML will be fetched. 
Also I am sure google would like it better this way :)
<pre class="lang-py prettyprint-override"><code>try:
 import httplib # python &lt; 3.0
except:
 import http.client as httplib


def have_internet():
 conn = httplib.HTTPSConnection(&quot;8.8.8.8&quot;, timeout=5)
 try:
 conn.request(&quot;HEAD&quot;, &quot;/&quot;)
 return True
 except Exception:
 return False
 finally:
 conn.close()
</code></pre>

blocks|key|4509947|text|import+urllib

def+connected(host='http://google.com'):
++++try:
++++++++urllib.urlopen(host)
++++++++return+True
++++except:
++++++++return+False

#+test
print(+'connected'+if+connected()+else+'no+internet!'+)|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|4509948|对于python+3，使用urllib.request.urlopen(host)|unstyled|offset|length|style|CODE|4509949|entityMap^0|0|D|S|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|N|8|@$G|O|H|P|I|J]]|9|@]|A|$]]|$1|K|3|-4|5|F|7|Q|8|@]|9|@]|A|$]]]|L|$]]

<pre><code>import urllib

def connected(host='http://google.com'):
 try:
 urllib.urlopen(host)
 return True
 except:
 return False

# test
print( 'connected' if connected() else 'no internet!' )
</code></pre>

For python 3, use <code>urllib.request.urlopen(host)</code>

blocks|key|1812188|text|以unutbu's+answer为起点，并在过去被“静态”IP地址更改烧毁，我创建了一个简单的类，使用DNS查找(即，使用URL+"https://www.google.com")检查一次，然后存储响应服务器的IP地址，以供后续检查使用。这样，IP地址始终是最新的(假设类至少每隔几年重新初始化一次)。我还把功劳归功于gawry+for+this+answer，它向我展示了如何获得服务器的IP地址(在任何重定向之后等)。请忽略这个解决方案的明显缺陷，在这里我将使用一个最小的工作示例。:)|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1812189|这就是我所拥有的：|1812190|import+socket

try:
++++from+urllib2+import+urlopen,+URLError
++++from+urlparse+import+urlparse
except+ImportError:++#+Python+3
++++from+urllib.parse+import+urlparse
++++from+urllib.request+import+urlopen,+URLError

class+InternetChecker(object):
++++conn_url+=+'https://www.google.com/'

++++def+__init__(self):
++++++++pass

++++def+test_internet(self):
++++++++try:
++++++++++++data+=+urlopen(self.conn_url,+timeout=5)
++++++++except+URLError:
++++++++++++return+False

++++++++try:
++++++++++++host+=+data.fp._sock.fp._sock.getpeername()
++++++++except+AttributeError:++#+Python+3
++++++++++++host+=+data.fp.raw._sock.getpeername()

++++++++#+Ensure+conn_url+is+an+IPv4+address+otherwise+future+queries+will+fail
++++++++self.conn_url+=+'http://'+%2B+(host[0]+if+len(host)+==+2+else
+++++++++++++++++++++++++++++++++++++socket.gethostbyname(urlparse(data.geturl()).hostname))

++++++++return+True

#+Usage+example
checker+=+InternetChecker()
checker.test_internet()|code-block|syntax|javascript|1812191|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/3764660/2747446|1|https://www.google.com/|2|https://stackoverflow.com/a/22512413/2747446^0|1|F|0|1U|M|1|4P|B|2|0|0|0^^$0|@$1|2|3|4|5|6|7|W|8|@]|9|@$A|X|B|Y|1|Z]|$A|10|B|11|1|12]|$A|13|B|14|1|15]]|C|$]]|$1|D|3|E|5|6|7|16|8|@]|9|@]|C|$]]|$1|F|3|G|5|H|7|17|8|@]|9|@]|C|$I|J]]|$1|K|3|-4|5|6|7|18|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]|U|$5|N|O|P|C|$Q|V]]]]

Taking <a href="https://stackoverflow.com/a/3764660/2747446">unutbu's answer</a> as a starting point, and having been burned in the past by a "static" IP address changing, I've made a simple class that checks once using a DNS lookup (i.e., using the URL "<a href="https://www.google.com" rel="nofollow noreferrer">https://www.google.com</a>"), and then stores the IP address of the responding server for use on subsequent checks. That way, the IP address is always up to date (assuming the class is re-initialized at least once every few years or so). I also give credit to gawry for <a href="https://stackoverflow.com/a/22512413/2747446">this answer</a>, which showed me how to get the server's IP address (after any redirection, etc.). Please disregard the apparent hackiness of this solution, I'm going for a minimal working example here. :)

Here is what I have:

<pre><code>import socket

try:
 from urllib2 import urlopen, URLError
 from urlparse import urlparse
except ImportError: # Python 3
 from urllib.parse import urlparse
 from urllib.request import urlopen, URLError

class InternetChecker(object):
 conn_url = 'https://www.google.com/'

 def __init__(self):
 pass

 def test_internet(self):
 try:
 data = urlopen(self.conn_url, timeout=5)
 except URLError:
 return False

 try:
 host = data.fp._sock.fp._sock.getpeername()
 except AttributeError: # Python 3
 host = data.fp.raw._sock.getpeername()

 # Ensure conn_url is an IPv4 address otherwise future queries will fail
 self.conn_url = 'http://' + (host[0] if len(host) == 2 else
 socket.gethostbyname(urlparse(data.geturl()).hostname))

 return True

# Usage example
checker = InternetChecker()
checker.test_internet()
</code></pre>

blocks|key|1067007|text|如果我们可以连接到某个Internet服务器，那么我们就确实有了连接。但是，为了实现最快、最可靠的方法，所有解决方案至少应符合以下要求：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1067008|1067009|避免DNS解析(我们将需要一个众所周知且保证大多数时间都可用的IP+)|unordered-list-item|1067010|避免应用层连接(连接到HTTP/FTP/IMAP服务)|1067011|避免从Python或其他选择的语言调用外部实用程序(我们需要想出一个不依赖于第三方解决方案的语言无关的解决方案)|1067012|1067013|要符合这些要求，一种方法可能是检查其中一个Google's+public+DNS+servers是否可达。这些服务器的IPv4地址为8.8.8.8和8.8.4.4。我们可以尝试连接他们中的任何一个。|offset|length|style|CODE|1067014|主机8.8.8.8的快速Nmap给出了以下结果：|1067015|$+sudo+nmap+8.8.8.8

Starting+Nmap+6.40+(+http://nmap.org+)+at+2015-10-14+10:17+IST
Nmap+scan+report+for+google-public-dns-a.google.com+(8.8.8.8)
Host+is+up+(0.0048s+latency).
Not+shown:+999+filtered+ports
PORT+++STATE+SERVICE
53/tcp+open++domain

Nmap+done:+1+IP+address+(1+host+up)+scanned+in+23.81+seconds|code-block|syntax|javascript|1067016|正如我们所看到的，53/tcp是开放的和非过滤的。如果您是非根用户，请记住使用sudo或Nmap的-Pn参数发送精心编制的探测数据包，并确定主机是否处于运行状态。|1067017|在尝试使用Python之前，让我们使用外部工具Netcat来测试连通性：|1067018|$+nc+8.8.8.8+53+-zv
Connection+to+8.8.8.8+53+port+[tcp/domain]+succeeded!|1067019|Netcat确认我们可以通过53/tcp连接到8.8.8.8。现在，我们可以在Python中设置到8.8.8.8:53/tcp的套接字连接，以检查连接：|1067020|import+socket

def+internet(host="8.8.8.8",+port=53,+timeout=3):
++++"""
++++Host:+8.8.8.8+(google-public-dns-a.google.com)
++++OpenPort:+53/tcp
++++Service:+domain+(DNS/TCP)
++++"""
++++try:
++++++++socket.setdefaulttimeout(timeout)
++++++++socket.socket(socket.AF_INET,+socket.SOCK_STREAM).connect((host,+port))
++++++++return+True
++++except+socket.error+as+ex:
++++++++print(ex)
++++++++return+False

internet()|1067021|另一种方法是向其中一台服务器发送手动创建的DNS探测，并等待响应。但是，我假设，由于数据包丢失，DNS解析失败等原因，它可能会被证明比较慢。如果你不这么认为，请发表评论。|1067022|更新#1:感谢@theamk的评论，timeout现在是一个参数，默认情况下初始化为3s。|1067023|更新#2:我做了快速测试，以确定这个问题的所有有效答案中最快和最通用的实现。总结如下：|1067024|$+ls+*.py+%7C+sort+-n+%7C+xargs+-I+%25+sh+-c+'echo+%25;+./timeit.sh+%25;+echo'
defos.py
True
00:00:00:00.487

iamaziz.py
True
00:00:00:00.335

ivelin.py
True
00:00:00:00.105

jaredb.py
True
00:00:00:00.533

kevinc.py
True
00:00:00:00.295

unutbu.py
True
00:00:00:00.546

7h3rAm.py
True
00:00:00:00.032|1067025|再一次：|1067026|$+ls+*.py+%7C+sort+-n+%7C+xargs+-I+%25+sh+-c+'echo+%25;+./timeit.sh+%25;+echo'
defos.py
True
00:00:00:00.450

iamaziz.py
True
00:00:00:00.358

ivelin.py
True
00:00:00:00.099

jaredb.py
True
00:00:00:00.585

kevinc.py
True
00:00:00:00.492

unutbu.py
True
00:00:00:00.485

7h3rAm.py
True
00:00:00:00.035|1067027|上面输出中的True表示来自各自作者的所有这些实现都正确地识别了到互联网的连接。时间以毫秒分辨率显示。|1067028|更新#3:在异常处理更改后再次测试：|1067029|defos.py
True
00:00:00:00.410

iamaziz.py
True
00:00:00:00.240

ivelin.py
True
00:00:00:00.109

jaredb.py
True
00:00:00:00.520

kevinc.py
True
00:00:00:00.317

unutbu.py
True
00:00:00:00.436

7h3rAm.py
True
00:00:00:00.030|1067030|entityMap|0|LINK|mutability|MUTABLE|url|https://developers.google.com/speed/public-dns/docs/using^0|0|0|0|0|0|0|1U|7|22|7|L|R|0|0|2|7|0|0|9|6|13|4|1D|3|0|0|0|E|6|N|7|1D|E|0|0|0|16|2|0|0|0|0|0|6|4|0|0|0^^$0|@$1|2|3|4|5|6|7|1X|8|@]|9|@]|A|$]]|$1|B|3|-4|5|6|7|1Y|8|@]|9|@]|A|$]]|$1|C|3|D|5|E|7|1Z|8|@]|9|@]|A|$]]|$1|F|3|G|5|E|7|20|8|@]|9|@]|A|$]]|$1|H|3|I|5|E|7|21|8|@]|9|@]|A|$]]|$1|J|3|-4|5|6|7|22|8|@]|9|@]|A|$]]|$1|K|3|L|5|6|7|23|8|@$M|24|N|25|O|P]|$M|26|N|27|O|P]]|9|@$M|28|N|29|1|2A]]|A|$]]|$1|Q|3|R|5|6|7|2B|8|@$M|2C|N|2D|O|P]]|9|@]|A|$]]|$1|S|3|T|5|U|7|2E|8|@]|9|@]|A|$V|W]]|$1|X|3|Y|5|6|7|2F|8|@$M|2G|N|2H|O|P]|$M|2I|N|2J|O|P]|$M|2K|N|2L|O|P]]|9|@]|A|$]]|$1|Z|3|10|5|6|7|2M|8|@]|9|@]|A|$]]|$1|11|3|12|5|U|7|2N|8|@]|9|@]|A|$V|W]]|$1|13|3|14|5|6|7|2O|8|@$M|2P|N|2Q|O|P]|$M|2R|N|2S|O|P]|$M|2T|N|2U|O|P]]|9|@]|A|$]]|$1|15|3|16|5|U|7|2V|8|@]|9|@]|A|$V|W]]|$1|17|3|18|5|6|7|2W|8|@]|9|@]|A|$]]|$1|19|3|1A|5|6|7|2X|8|@$M|2Y|N|2Z|O|P]]|9|@]|A|$]]|$1|1B|3|1C|5|6|7|30|8|@]|9|@]|A|$]]|$1|1D|3|1E|5|U|7|31|8|@]|9|@]|A|$V|W]]|$1|1F|3|1G|5|6|7|32|8|@]|9|@]|A|$]]|$1|1H|3|1I|5|U|7|33|8|@]|9|@]|A|$V|W]]|$1|1J|3|1K|5|6|7|34|8|@$M|35|N|36|O|P]]|9|@]|A|$]]|$1|1L|3|1M|5|6|7|37|8|@]|9|@]|A|$]]|$1|1N|3|1O|5|U|7|38|8|@]|9|@]|A|$V|W]]|$1|1P|3|-4|5|6|7|39|8|@]|9|@]|A|$]]]|1Q|$1R|$5|1S|1T|1U|A|$1V|1W]]]]

If we can connect to some Internet server, then we indeed have connectivity. However, for the fastest and most reliable approach, all solutions should comply with the following requirements, at the very least:
<ul>
<li>Avoid DNS resolution (we will need an IP that is well-known and guaranteed to be available for most of the time)</li>
<li>Avoid application layer connections (connecting to an HTTP/FTP/IMAP service)</li>
<li>Avoid calls to external utilities from Python or other language of choice (we need to come up with a language-agnostic solution that doesn't rely on third-party solutions)</li>
</ul>
To comply with these, one approach could be to, check if one of the <a href="https://developers.google.com/speed/public-dns/docs/using" rel="noreferrer">Google's public DNS servers</a> is reachable. The IPv4 addresses for these servers are <code>8.8.8.8</code> and <code>8.8.4.4</code>. We can try connecting to any of them.
A quick Nmap of the host <code>8.8.8.8</code> gave below result:
<pre><code>$ sudo nmap 8.8.8.8

Starting Nmap 6.40 ( http://nmap.org ) at 2015-10-14 10:17 IST
Nmap scan report for google-public-dns-a.google.com (8.8.8.8)
Host is up (0.0048s latency).
Not shown: 999 filtered ports
PORT STATE SERVICE
53/tcp open domain

Nmap done: 1 IP address (1 host up) scanned in 23.81 seconds
</code></pre>
As we can see, <code>53/tcp</code> is open and non-filtered. If you are a non-root user, remember to use <code>sudo</code> or the <code>-Pn</code> argument for Nmap to send crafted probe packets and determine if a host is up.
Before we try with Python, let's test connectivity using an external tool, Netcat:
<pre><code>$ nc 8.8.8.8 53 -zv
Connection to 8.8.8.8 53 port [tcp/domain] succeeded!
</code></pre>
Netcat confirms that we can reach <code>8.8.8.8</code> over <code>53/tcp</code>. Now we can set up a socket connection to <code>8.8.8.8:53/tcp</code> in Python to check connection:
<pre class="lang-py prettyprint-override"><code>import socket

def internet(host=&quot;8.8.8.8&quot;, port=53, timeout=3):
 &quot;&quot;&quot;
 Host: 8.8.8.8 (google-public-dns-a.google.com)
 OpenPort: 53/tcp
 Service: domain (DNS/TCP)
 &quot;&quot;&quot;
 try:
 socket.setdefaulttimeout(timeout)
 socket.socket(socket.AF_INET, socket.SOCK_STREAM).connect((host, port))
 return True
 except socket.error as ex:
 print(ex)
 return False

internet()
</code></pre>
Another approach could be to send a manually crafted DNS probe to one of these servers and wait for a response. But, I assume, it might prove slower in comparison due to packet drops, DNS resolution failure, etc. Please comment if you think otherwise.
UPDATE #1: Thanks to @theamk's comment, timeout is now an argument and initialized to <code>3s</code> by default.
UPDATE #2: I did quick tests to identify the fastest and most generic implementation of all valid answers to this question. Here's the summary:
<pre><code>$ ls *.py | sort -n | xargs -I % sh -c 'echo %; ./timeit.sh %; echo'
defos.py
True
00:00:00:00.487

iamaziz.py
True
00:00:00:00.335

ivelin.py
True
00:00:00:00.105

jaredb.py
True
00:00:00:00.533

kevinc.py
True
00:00:00:00.295

unutbu.py
True
00:00:00:00.546

7h3rAm.py
True
00:00:00:00.032
</code></pre>
And once more:
<pre><code>$ ls *.py | sort -n | xargs -I % sh -c 'echo %; ./timeit.sh %; echo'
defos.py
True
00:00:00:00.450

iamaziz.py
True
00:00:00:00.358

ivelin.py
True
00:00:00:00.099

jaredb.py
True
00:00:00:00.585

kevinc.py
True
00:00:00:00.492

unutbu.py
True
00:00:00:00.485

7h3rAm.py
True
00:00:00:00.035
</code></pre>
<code>True</code> in the above output signifies that all these implementations from respective authors correctly identify connectivity to the Internet. Time is shown with milliseconds resolution.
UPDATE #3: Tested again after the exception handling change:
<pre><code>defos.py
True
00:00:00:00.410

iamaziz.py
True
00:00:00:00.240

ivelin.py
True
00:00:00:00.109

jaredb.py
True
00:00:00:00.520

kevinc.py
True
00:00:00:00.317

unutbu.py
True
00:00:00:00.436

7h3rAm.py
True
00:00:00:00.030
</code></pre>

blocks|key|4510122|text|如果本地主机已从127.0.0.1+Try更改，则这可能不起作用|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|4510123|import+socket
ipaddress=socket.gethostbyname(socket.gethostname())
if+ipaddress=="127.0.0.1":
++++print("You+are+not+connected+to+the+internet!")
else:
++++print("You+are+connected+to+the+internet+with+the+IP+address+of+"%2B+ipaddress+)|code-block|syntax|javascript|4510124|除非经过编辑，否则未连接到internet时，您的计算机的IP地址将为127.0.0.1。这段代码主要是获取IP地址，然后询问它是否是本地主机IP地址。希望这能有所帮助|4510125|entityMap^0|8|9|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@$9|P|A|Q|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|R|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|D|@]|E|$]]|$1|M|3|-4|5|6|7|T|8|@]|D|@]|E|$]]]|N|$]]

This might not work if the localhost has been changed from <code>127.0.0.1</code>
Try 

<pre><code>import socket
ipaddress=socket.gethostbyname(socket.gethostname())
if ipaddress=="127.0.0.1":
 print("You are not connected to the internet!")
else:
 print("You are connected to the internet with the IP address of "+ ipaddress )
</code></pre>

Unless edited , your computers IP will be 127.0.0.1 when not connected to the internet.
This code basically gets the IP address and then asks if it is the localhost IP address .
Hope that helps

blocks|key|1069075|text|在集群上运行脚本或不运行脚本时，我最喜欢的一个|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1069076|import+subprocess

def+online(timeout):
++++try:
++++++++return+subprocess.run(
++++++++++++['wget',+'-q',+'--spider',+'google.com'],
++++++++++++timeout=timeout
++++++++).returncode+==+0
++++except+subprocess.TimeoutExpired:
++++++++return+False|code-block|syntax|javascript|1069077|这会安静地运行wget，不会下载任何内容，但会检查给定的远程文件是否存在于web上|1069078|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

my favorite one, when running scripts on a cluster or not

<pre><code>import subprocess

def online(timeout):
 try:
 return subprocess.run(
 ['wget', '-q', '--spider', 'google.com'],
 timeout=timeout
 ).returncode == 0
 except subprocess.TimeoutExpired:
 return False
</code></pre>

this runs wget quietly, not downloading anything but checking that the given remote file exists on the web

blocks|key|4510222|text|采用Six的答案我认为我们可以以某种方式简化，这是一个重要的问题，因为新手迷失在高度技术性的问题中。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4510223|在这里，我最终将使用它来等待我的连接(3G，慢速)每天建立一次，用于我的PV监控。|4510224|与Raspbian3.4.2一起在Pyth3下工作|4510225|from+urllib.request+import+urlopen
from+time+import+sleep
urltotest=http://www.lsdx.eu+++++++++++++#+my+own+web+page
nboftrials=0
answer='NO'
while+answer=='NO'+and+nboftrials<10:
++++try:
++++++++urlopen(urltotest)
++++++++answer='YES'
++++except:
++++++++essai='NO'
++++++++nboftrials%2B=1
++++++++sleep(30)+++++++|code-block|syntax|javascript|4510226|最大运行时间:5分钟，如果达到，我会在一个小时的时间内尝试，但这是另一种脚本！|4510227|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|P|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|Q|8|@]|9|@]|A|$]]|$1|F|3|G|5|H|7|R|8|@]|9|@]|A|$I|J]]|$1|K|3|L|5|6|7|S|8|@]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Taking Six' answer I think we could simplify somehow, an important issue as newcomers are lost in highly technical matters.

Here what I finally will use to wait for my connection (3G, slow) to be established once a day for my PV monitoring.

Works under Pyth3 with Raspbian 3.4.2

<pre><code>from urllib.request import urlopen
from time import sleep
urltotest=http://www.lsdx.eu # my own web page
nboftrials=0
answer='NO'
while answer=='NO' and nboftrials&lt;10:
 try:
 urlopen(urltotest)
 answer='YES'
 except:
 essai='NO'
 nboftrials+=1
 sleep(30) 
</code></pre>

maximum running: 5 minutes if reached I will try in one hour's time but its another bit of script!

blocks|key|3099535|text|要做到这一点，最好的方法是让它检查一个IP地址，如果python找不到网站，它总是给出一个IP地址。在这种情况下，这是我的代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3099536|import+socket

print("website+connection+checker")
while+True:
++++website+=+input("please+input+website:+")
++++print("")
++++print(socket.gethostbyname(website))
++++if+socket.gethostbyname(website)+==+"92.242.140.2":
++++++++print("Website+could+be+experiencing+an+issue/Doesn't+exist")
++++else:
++++++++socket.gethostbyname(website)
++++++++print("Website+is+operational!")
++++++++print("")|code-block|syntax|javascript|3099537|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Best way to do this is to make it check against an IP address that python always gives if it can't find the website. In this case this is my code:

<pre><code>import socket

print("website connection checker")
while True:
 website = input("please input website: ")
 print("")
 print(socket.gethostbyname(website))
 if socket.gethostbyname(website) == "92.242.140.2":
 print("Website could be experiencing an issue/Doesn't exist")
 else:
 socket.gethostbyname(website)
 print("Website is operational!")
 print("")
</code></pre>

blocks|key|3099574|text|获取Ivelin's+answer并添加一些额外检查，因为我的路由器在查询google.com时提供其ip地址192.168.0.1，如果没有internet连接，则返回报头。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|3099575|import+socket

def+haveInternet():
++++try:
++++++++#+first+check+if+we+get+the+correct+IP-Address+or+just+the+router's+IP-Address
++++++++info+=+socket.getaddrinfo("www.google.com",+None)[0]
++++++++ipAddr+=+info[4][0]
++++++++if+ipAddr+==+"192.168.0.1"+:
++++++++++++return+False
++++except:
++++++++return+False

++++conn+=+httplib.HTTPConnection("www.google.com",+timeout=5)
++++try:
++++++++conn.request("HEAD",+"/")
++++++++conn.close()
++++++++return+True
++++except:
++++++++conn.close()
++++++++return+False|code-block|syntax|javascript|3099576|entityMap|0|LINK|mutability|MUTABLE|url|https://stackoverflow.com/a/29854274/3357935^0|2|F|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@$A|R|B|S|1|T]]|C|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|C|$G|H]]|$1|I|3|-4|5|6|7|V|8|@]|9|@]|C|$]]]|J|$K|$5|L|M|N|C|$O|P]]]]

Taking <a href="https://stackoverflow.com/a/29854274/3357935">Ivelin's answer</a> and add some extra check as my router delivers its ip address 192.168.0.1 and returns a head if it has no internet connection when querying google.com.

<pre><code>import socket

def haveInternet():
 try:
 # first check if we get the correct IP-Address or just the router's IP-Address
 info = socket.getaddrinfo("www.google.com", None)[0]
 ipAddr = info[4][0]
 if ipAddr == "192.168.0.1" :
 return False
 except:
 return False

 conn = httplib.HTTPConnection("www.google.com", timeout=5)
 try:
 conn.request("HEAD", "/")
 conn.close()
 return True
 except:
 conn.close()
 return False
</code></pre>

blocks|key|4510340|text|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4510341|这是我的版本|blockquote|4510342|4510343|4510344|import+requests

try:
++++if+requests.get('https://google.com').ok:
++++++++print("You're+Online")
except:
++++print("You're+Offline")|code-block|syntax|javascript|4510345|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|-4|4|5|6|M|7|@]|8|@]|9|$]]|$1|A|3|B|4|C|6|N|7|@]|8|@]|9|$]]|$1|D|3|-4|4|5|6|O|7|@]|8|@]|9|$]]|$1|E|3|-4|4|5|6|P|7|@]|8|@]|9|$]]|$1|F|3|G|4|H|6|Q|7|@]|8|@]|9|$I|J]]|$1|K|3|-4|4|5|6|R|7|@]|8|@]|9|$]]]|L|$]]

<blockquote>
 Here's my version 
</blockquote>

<pre><code>import requests

try:
 if requests.get('https://google.com').ok:
 print("You're Online")
except:
 print("You're Offline")
</code></pre>

blocks|key|1069165|text|这对我在Python3.6中是有效的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1069166|import+urllib
from+urllib.request+import+urlopen


def+is_internet():
++++"""
++++Query+internet+using+python
++++:return:
++++"""
++++try:
++++++++urlopen('https://www.google.com',+timeout=1)
++++++++return+True
++++except+urllib.error.URLError+as+Error:
++++++++print(Error)
++++++++return+False


if+is_internet():
++++print("Internet+is+active")
else:
++++print("Internet+disconnected")|code-block|syntax|javascript|1069167|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

This works for me in Python3.6

<pre><code>import urllib
from urllib.request import urlopen


def is_internet():
 """
 Query internet using python
 :return:
 """
 try:
 urlopen('https://www.google.com', timeout=1)
 return True
 except urllib.error.URLError as Error:
 print(Error)
 return False


if is_internet():
 print("Internet is active")
else:
 print("Internet disconnected")
</code></pre>

blocks|key|3099633|text|使用requests的现代便携解决方案|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|3099634|import+requests

def+internet():
++++"""Detect+an+internet+connection."""

++++connection+=+None
++++try:
++++++++r+=+requests.get("https://google.com")
++++++++r.raise_for_status()
++++++++print("Internet+connection+detected.")
++++++++connection+=+True
++++except:
++++++++print("Internet+connection+not+detected.")
++++++++connection+=+False
++++finally:
++++++++return+connection|code-block|syntax|javascript|3099635|或者，引发异常的版本：|3099636|import+requests
from+requests.exceptions+import+ConnectionError

def+internet():
++++"""Detect+an+internet+connection."""

++++try:
++++++++r+=+requests.get("https://google.com")
++++++++r.raise_for_status()
++++++++print("Internet+connection+detected.")
++++except+ConnectionError+as+e:
++++++++print("Internet+connection+not+detected.")
++++++++raise+e|3099637|entityMap^0|2|8|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@$9|R|A|S|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|T|8|@]|D|@]|E|$I|J]]|$1|K|3|L|5|6|7|U|8|@]|D|@]|E|$]]|$1|M|3|N|5|H|7|V|8|@]|D|@]|E|$I|J]]|$1|O|3|-4|5|6|7|W|8|@]|D|@]|E|$]]]|P|$]]

A modern portable solution with <code>requests</code>:

<pre class="lang-py prettyprint-override"><code>import requests

def internet():
 """Detect an internet connection."""

 connection = None
 try:
 r = requests.get("https://google.com")
 r.raise_for_status()
 print("Internet connection detected.")
 connection = True
 except:
 print("Internet connection not detected.")
 connection = False
 finally:
 return connection
</code></pre>

Or, a version that raises an exception:

<pre class="lang-py prettyprint-override"><code>import requests
from requests.exceptions import ConnectionError

def internet():
 """Detect an internet connection."""

 try:
 r = requests.get("https://google.com")
 r.raise_for_status()
 print("Internet connection detected.")
 except ConnectionError as e:
 print("Internet connection not detected.")
 raise e
</code></pre>

blocks|key|3099645|text|我在Joel的代码中添加了一些。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|3099646|++++import+socket,time
++++mem1+=+0
++++while+True:
++++++++try:
++++++++++++++++host+=+socket.gethostbyname("www.google.com")+#Change+to+personal+choice+of+site
++++++++++++++++s+=+socket.create_connection((host,+80),+2)
++++++++++++++++s.close()
++++++++++++++++mem2+=+1
++++++++++++++++if+(mem2+==+mem1):
++++++++++++++++++++pass+#Add+commands+to+be+executed+on+every+check
++++++++++++++++else:
++++++++++++++++++++mem1+=+mem2
++++++++++++++++++++print+("Internet+is+working")+#Will+be+executed+on+state+change

++++++++except+Exception+as+e:
++++++++++++++++mem2+=+0
++++++++++++++++if+(mem2+==+mem1):
++++++++++++++++++++pass
++++++++++++++++else:
++++++++++++++++++++mem1+=+mem2
++++++++++++++++++++print+("Internet+is+down")
++++++++time.sleep(10)+#timeInterval+for+checking|code-block|syntax|javascript|3099647|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

I added a few to Joel's code.

<pre class="lang-py prettyprint-override"><code> import socket,time
 mem1 = 0
 while True:
 try:
 host = socket.gethostbyname("www.google.com") #Change to personal choice of site
 s = socket.create_connection((host, 80), 2)
 s.close()
 mem2 = 1
 if (mem2 == mem1):
 pass #Add commands to be executed on every check
 else:
 mem1 = mem2
 print ("Internet is working") #Will be executed on state change

 except Exception as e:
 mem2 = 0
 if (mem2 == mem1):
 pass
 else:
 mem1 = mem2
 print ("Internet is down")
 time.sleep(10) #timeInterval for checking
</code></pre>

blocks|key|4510430|text|对于我的项目，我使用script+modified来ping+google+public+DNS服务器8.8.8.8。使用1秒的超时和没有外部依赖的核心python库：|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4510431|import+struct
import+socket
import+select


def+send_one_ping(to='8.8.8.8'):
+++ping_socket+=+socket.socket(socket.AF_INET,+socket.SOCK_RAW,+socket.getprotobyname('icmp'))
+++checksum+=+49410
+++header+=+struct.pack('!BBHHH',+8,+0,+checksum,+0x123,+1)
+++data+=+b'BCDEFGHIJKLMNOPQRSTUVWXYZ[\\]%5E_`abcdefghijklmnopqrstuvwx'
+++header+=+struct.pack(
++++++'!BBHHH',+8,+0,+checksum,+0x123,+1
+++)
+++packet+=+header+%2B+data
+++ping_socket.sendto(packet,+(to,+1))
+++inputready,+_,+_+=+select.select([ping_socket],+[],+[],+1.0)
+++if+inputready+==+[]:
++++++raise+Exception('No+internet')+##+or+return+False
+++_,+address+=+ping_socket.recvfrom(2048)
+++print(address)+##+or+return+True


send_one_ping()|code-block|syntax|javascript|4510432|select超时值是1，但可以是一个浮点数，它比本例中的1秒更容易失败。|4510433|entityMap|0|LINK|mutability|MUTABLE|url|https://github.com/Akhavi/pyping/blob/master/pyping/core.py|1|https://docs.python.org/3/library/select.html#select.select^0|A|F|0|0|0|0|6|1|0^^$0|@$1|2|3|4|5|6|7|U|8|@]|9|@$A|V|B|W|1|X]]|C|$]]|$1|D|3|E|5|F|7|Y|8|@]|9|@]|C|$G|H]]|$1|I|3|J|5|6|7|Z|8|@]|9|@$A|10|B|11|1|12]]|C|$]]|$1|K|3|-4|5|6|7|13|8|@]|9|@]|C|$]]]|L|$M|$5|N|O|P|C|$Q|R]]|S|$5|N|O|P|C|$Q|T]]]]

For my projects I use <a href="https://github.com/Akhavi/pyping/blob/master/pyping/core.py" rel="nofollow noreferrer">script modified</a> to ping the google public DNS server 8.8.8.8. Using a timeout of 1 second and core python libraries with no external dependencies:

<pre><code>import struct
import socket
import select


def send_one_ping(to='8.8.8.8'):
 ping_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, socket.getprotobyname('icmp'))
 checksum = 49410
 header = struct.pack('!BBHHH', 8, 0, checksum, 0x123, 1)
 data = b'BCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`abcdefghijklmnopqrstuvwx'
 header = struct.pack(
 '!BBHHH', 8, 0, checksum, 0x123, 1
 )
 packet = header + data
 ping_socket.sendto(packet, (to, 1))
 inputready, _, _ = select.select([ping_socket], [], [], 1.0)
 if inputready == []:
 raise Exception('No internet') ## or return False
 _, address = ping_socket.recvfrom(2048)
 print(address) ## or return True


send_one_ping()
</code></pre>

The <a href="https://docs.python.org/3/library/select.html#select.select" rel="nofollow noreferrer">select</a> timeout value is 1, but can be a floating point number of choice to fail more readily than the 1 second in this example.

blocks|key|4510447|text|导入请求并尝试使用这个简单的python代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4510448|def+check_internet():
++++url+=+'http://www.google.com/'
++++timeout+=+5
++++try:
++++++++_+=+requests.get(url,+timeout=timeout)
++++++++return+True
++++except+requests.ConnectionError:
++++++++return+False|code-block|syntax|javascript|4510449|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

import requests and try this simple python code.
<pre><code>def check_internet():
 url = 'http://www.google.com/'
 timeout = 5
 try:
 _ = requests.get(url, timeout=timeout)
 return True
 except requests.ConnectionError:
 return False
</code></pre>

blocks|key|1069212|text|通过运行以下命令确保pip是最新的|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1069213|pip+install+--upgrade+pip|code-block|syntax|javascript|1069214|使用以下命令安装请求包|1069215|pip+install+requests++|1069216|++++import+requests
++++import+webbrowser
++++url+=+"http://www.youtube.com"

++++timeout+=+6
++++try:
++++++++request+=+requests.get(url,+timeout=timeout)
++++++++print("Connected+to+the+Internet")
++++++++print("browser+is+loading+url")
++++++++webbrowser.open(url)
++++except+(requests.ConnectionError,+requests.Timeout)+as+exception:
+++++++print("poor+or+no+internet+connection.")|1069217|entityMap^0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|D|7|S|8|@]|9|@]|A|$E|F]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

Make sure your pip is up to date by running
<pre class="lang-py prettyprint-override"><code>pip install --upgrade pip
</code></pre>
Install the requests package using
<pre class="lang-py prettyprint-override"><code>pip install requests 
</code></pre>
<pre class="lang-py prettyprint-override"><code> import requests
 import webbrowser
 url = &quot;http://www.youtube.com&quot;

 timeout = 6
 try:
 request = requests.get(url, timeout=timeout)
 print(&quot;Connected to the Internet&quot;)
 print(&quot;browser is loading url&quot;)
 webbrowser.open(url)
 except (requests.ConnectionError, requests.Timeout) as exception:
 print(&quot;poor or no internet connection.&quot;)
</code></pre>

I want to see if I can access an online API, but for that, I need to have Internet access.
How can I see if there's a connection available and active using Python?

How can I see if there's an available and active network connection in Python?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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我想看看我是否可以访问在线API，但为了实现这一点，我需要有Internet访问权限。如何使用Python查看是否有可用的活动连接？

问如何查看Python中是否有可用的活动网络连接？
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问如何查看Python中是否有可用的活动网络连接？EN