使用 python 访问 ECMWF 数据库时出错

Question

我正在尝试访问 ECMWF 数据库并使用 python 下载一组简单的数据。尽管我遵循了网站上非常简单的说明：https://software.ecmwf.int/wiki/display/CKB/How+to+download+ERA-Interim+data+from+the+ECMWF+data+archive

我收到以下错误。

如何解决？

您还可以在下面找到使用的示例代码

我在 Windows 8 上使用 python 3.6.5

================== RESTART: C:\Users\Giulio\Desktop\test.py ==================
2018-05-21 12:08:29 ECMWF API python library 1.5.0
2018-05-21 12:08:29 ECMWF API at https://api.ecmwf.int/v1
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Error contacting the WebAPI, retrying in 60 seconds ...
Could not contact the WebAPI after 10 tries, failing !
Traceback (most recent call last):
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\urllib\request.py", line 1318, in do_open
    encode_chunked=req.has_header('Transfer-encoding'))
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\http\client.py", line 1239, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\http\client.py", line 1285, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\http\client.py", line 1234, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\http\client.py", line 1026, in _send_output
    self.send(msg)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\http\client.py", line 964, in send
    self.connect()
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\http\client.py", line 1400, in connect
    server_hostname=server_hostname)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\ssl.py", line 407, in wrap_socket
    _context=self, _session=session)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\ssl.py", line 814, in __init__
    self.do_handshake()
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\ssl.py", line 1068, in do_handshake
    self._sslobj.do_handshake()
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\ssl.py", line 689, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:833)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Giulio\Desktop\test.py", line 19, in <module>
    "target": "test.nc"
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\site-packages\ecmwfapi\api.py", line 519, in retrieve
    c = APIRequest(self.url, "datasets/%s" % (dataset,), self.email, self.key, self.trace, verbose=self.verbose)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\site-packages\ecmwfapi\api.py", line 391, in __init__
    user = self.connection.call("%s/%s" % (self.url, "who-am-i"))
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\site-packages\ecmwfapi\api.py", line 172, in wrapped
    raise last_error
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\site-packages\ecmwfapi\api.py", line 140, in wrapped
    return func(self, *args, **kwargs)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\site-packages\ecmwfapi\api.py", line 273, in call
    res = opener.open(req)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\urllib\request.py", line 526, in open
    response = self._open(req, data)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\urllib\request.py", line 544, in _open
    '_open', req)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\urllib\request.py", line 504, in _call_chain
    result = func(*args)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\urllib\request.py", line 1361, in https_open
    context=self._context, check_hostname=self._check_hostname)
  File "C:\Users\Giulio\AppData\Local\Programs\Python\Python36\lib\urllib\request.py", line 1320, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:833)>

示例脚本：

#!/usr/bin/env python
from ecmwfapi import ECMWFDataServer

server = ECMWFDataServer()
server.retrieve({
    "class": "ei",
    "dataset": "interim",
    "expver": "1",
    "stream": "oper",
    "type": "fc",
    "levtype": "sfc",
    "param": "167.128",
    "date": "2017-08-01/to/2017-08-03",
    "time": "00:00:00",
    "step": "3",
    "grid": "0.75/0.75",
    "area":"75/-20/10/60",
    "format":"netcdf",
    "target": "test.nc"
})

Answer 1

我通过以下链接解决了这个问题：https://software.ecmwf.int/wiki/display/WEBAPI/Web-API+Troubleshooting#Web-APITroubleshooting-3.2.1.3WARNING:httplib2.URLErrorreceivedNone%3Curlopenerror[SSL:CERTIFICATE_VERIFY_FAILED]certificateverifyfailed

问题可能是 Python 版本中使用的 SSL 库没有在正确的证书路径中查找。

就我而言，必须更新 ca 证书

QuoVadis Root CA 2 G3 是 api.ecmwf.int 的根 CA，可以从 https://www.quovadisglobal.com/QVRepository/DownloadRootsAndCRL.aspx 下载并安装在本地。

对于 Windows，可以通过以下步骤完成：

1.在windows菜单搜索栏输入mmc.exe

2.转到文件>添加/删除管理单元>选择证书>单击添加>单击确定

3.扩展证书 - 当前用户

4.右键单击受信任的根证书颁发机构>所有任务>导入

5.按照步骤操作

或者

certutil -addstore -f "ROOT" new-root-certificate.crt

在命令提示符下

Answer 2

我遇到了完全相同的问题。

我的设置：Windows 10 和 Python 3.6。

我通过直接修改源代码解决了它（非最佳解决方案，但可行）。这是为了忽略证书验证。

打开：~/Lib/site-packages/ecmwfapi/api.py

在脚本的开头，添加：

import ssl

在“_transfer”函数的开头添加：

ctx = ssl.create_default_context ()
ctx.check_hostname = False
ctx.verify_mode = ssl.CERT_NONE

然后修改（总是在函数内）： urlopen（请求） 作者：

urlopen (req, context = ctx)

来源：python ignore certificate validation urllib2

欢呼！