Python–urllib3库详解

Python–urllib3库中文详解

User Guide(英文)

Making requests

First things first, import the urllib3 module:

>>> import urllib3

You’ll need a 

<span class="pre">PoolManager</span>

 instance to make requests. This object handles all of the details of connection pooling and thread safety so that you don’t have to:

>>> http = urllib3.PoolManager()

To make a request use 

<span class="pre">request()</span>

:

>>> r = http.request('GET', 'http://httpbin.org/robots.txt')
>>> r.data
b'User-agent: *\nDisallow: /deny\n'
<span class="pre">request()</span>

 returns a 

<span class="pre">HTTPResponse</span>

 object, the Response content section explains how to handle various responses.

You can use 

<span class="pre">request()</span>

 to make requests using any HTTP verb:

>>> r = http.request(
...     'POST',
...     'http://httpbin.org/post',
...     fields={'hello': 'world'})

The Request data section covers sending other kinds of requests data, including JSON, files, and binary data.

Response content

The 

<span class="pre">HTTPResponse</span>

 object provides 

<span class="pre">status</span>

<span class="pre">data</span>

, and 

<span class="pre">header</span>

 attributes:

>>> r = http.request('GET', 'http://httpbin.org/ip')
>>> r.status
200
>>> r.data
b'{\n  "origin": "104.232.115.37"\n}\n'
>>> r.headers
HTTPHeaderDict({'Content-Length': '33', ...})

JSON content

JSON content can be loaded by decoding and deserializing the 

<span class="pre">data</span>

 attribute of the request:

>>> import json
>>> r = http.request('GET', 'http://httpbin.org/ip')
>>> json.loads(r.data.decode('utf-8'))
{'origin': '127.0.0.1'}

Binary content

The 

<span class="pre">data</span>

 attribute of the response is always set to a byte string representing the response content:

>>> r = http.request('GET', 'http://httpbin.org/bytes/8')
>>> r.data
b'\xaa\xa5H?\x95\xe9\x9b\x11'

Note

For larger responses, it’s sometimes better to stream the response.

Request data

Headers

You can specify headers as a dictionary in the 

<span class="pre">headers</span>

 argument in 

<span class="pre">request()</span>

:

>>> r = http.request(
...     'GET',
...     'http://httpbin.org/headers',
...     headers={
...         'X-Something': 'value'
...     })
>>> json.loads(r.data.decode('utf-8'))['headers']
{'X-Something': 'value', ...}

Query parameters

For 

<span class="pre">GET</span>

<span class="pre">HEAD</span>

, and 

<span class="pre">DELETE</span>

 requests, you can simply pass the arguments as a dictionary in the 

<span class="pre">fields</span>

 argument to 

<span class="pre">request()</span>

:

>>> r = http.request(
...     'GET',
...     'http://httpbin.org/get',
...     fields={'arg': 'value'})
>>> json.loads(r.data.decode('utf-8'))['args']
{'arg': 'value'}

For 

<span class="pre">POST</span>

 and 

<span class="pre">PUT</span>

 requests, you need to manually encode query parameters in the URL:

>>> from urllib.parse import urlencode
>>> encoded_args = urlencode({'arg': 'value'})
>>> url = 'http://httpbin.org/post?' + encoded_args
>>> r = http.request('POST', url)
>>> json.loads(r.data.decode('utf-8'))['args']
{'arg': 'value'}

Form data

For 

<span class="pre">PUT</span>

 and 

<span class="pre">POST</span>

 requests, urllib3 will automatically form-encode the dictionary in the 

<span class="pre">fields</span>

 argument provided to 

<span class="pre">request()</span>

:

>>> r = http.request(
...     'POST',
...     'http://httpbin.org/post',
...     fields={'field': 'value'})
>>> json.loads(r.data.decode('utf-8'))['form']
{'field': 'value'}

JSON

You can send a JSON request by specifying the encoded data as the 

<span class="pre">body</span>

 argument and setting the 

<span class="pre">Content-Type</span>

 header when calling 

<span class="pre">request()</span>

:

>>> import json
>>> data = {'attribute': 'value'}
>>> encoded_data = json.dumps(data).encode('utf-8')
>>> r = http.request(
...     'POST',
...     'http://httpbin.org/post',
...     body=encoded_data,
...     headers={'Content-Type': 'application/json'})
>>> json.loads(r.data.decode('utf-8'))['json']
{'attribute': 'value'}

Files & binary data

For uploading files using 

<span class="pre">multipart/form-data</span>

 encoding you can use the same approach as Form data and specify the file field as a tuple of 

<span class="pre">(file_name,</span><span class="pre">file_data)</span>

:

>>> with open('example.txt') as fp:
...     file_data = fp.read()
>>> r = http.request(
...     'POST',
...     'http://httpbin.org/post',
...     fields={
...         'filefield': ('example.txt', file_data),
...     })
>>> json.loads(r.data.decode('utf-8'))['files']
{'filefield': '...'}

While specifying the filename is not strictly required, it’s recommended in order to match browser behavior. You can also pass a third item in the tuple to specify the file’s MIME type explicitly:

>>> r = http.request(
...     'POST',
...     'http://httpbin.org/post',
...     fields={
...         'filefield': ('example.txt', file_data, 'text/plain'),
...     })

For sending raw binary data simply specify the 

<span class="pre">body</span>

 argument. It’s also recommended to set the 

<span class="pre">Content-Type</span>

 header:

>>> with open('example.jpg', 'rb') as fp:
...     binary_data = fp.read()
>>> r = http.request(
...     'POST',
...     'http://httpbin.org/post',
...     body=binary_data,
...     headers={'Content-Type': 'image/jpeg'})
>>> json.loads(r.data.decode('utf-8'))['data']
b'...'

Certificate verification

Note

New in version 1.25

HTTPS connections are now verified by default (

<span class="pre">cert_reqs</span> <span class="pre">=</span><span class="pre">'CERT_REQUIRED'</span>

).

While you can disable certification verification, it is highly recommend to leave it on.

Unless otherwise specified urllib3 will try to load the default system certificate stores. The most reliable cross-platform method is to use the certifi package which provides Mozilla’s root certificate bundle:

pip install certifi

You can also install certifi along with urllib3 by using the 

<span class="pre">secure</span>

 extra:

pip install urllib3[secure]

Warning

If you’re using Python 2 you may need additional packages. See the section below for more details.

Once you have certificates, you can create a 

<span class="pre">PoolManager</span>

 that verifies certificates when making requests:

>>> import certifi
>>> import urllib3
>>> http = urllib3.PoolManager(
...     cert_reqs='CERT_REQUIRED',
...     ca_certs=certifi.where())

The 

<span class="pre">PoolManager</span>

 will automatically handle certificate verification and will raise 

<span class="pre">SSLError</span>

 if verification fails:

>>> http.request('GET', 'https://google.com')
(No exception)
>>> http.request('GET', 'https://expired.badssl.com')
urllib3.exceptions.SSLError ...

Note

You can use OS-provided certificates if desired. Just specify the full path to the certificate bundle as the 

<span class="pre">ca_certs</span>

 argument instead of

<span class="pre">certifi.where()</span>

. For example, most Linux systems store the certificates at 

<span class="pre">/etc/ssl/certs/ca-certificates.crt</span>

. Other operating systems can be difficult.

Certificate verification in Python 2

Older versions of Python 2 are built with an 

<span class="pre">ssl</span>

 module that lacks SNI support and can lag behind security updates. For these reasons it’s recommended to usepyOpenSSL.

If you install urllib3 with the 

<span class="pre">secure</span>

 extra, all required packages for certificate verification on Python 2 will be installed:

pip install urllib3[secure]

If you want to install the packages manually, you will need 

<span class="pre">pyOpenSSL</span>

,

<span class="pre">cryptography</span>

<span class="pre">idna</span>

, and 

<span class="pre">certifi</span>

.

Note

If you are not using macOS or Windows, note that cryptography requires additional system packages to compile. See building cryptography on Linuxfor the list of packages required.

Once installed, you can tell urllib3 to use pyOpenSSL by using 

<span class="pre">urllib3.contrib.pyopenssl</span>

:

>>> import urllib3.contrib.pyopenssl
>>> urllib3.contrib.pyopenssl.inject_into_urllib3()

Finally, you can create a 

<span class="pre">PoolManager</span>

 that verifies certificates when performing requests:

>>> import certifi
>>> import urllib3
>>> http = urllib3.PoolManager(
...     cert_reqs='CERT_REQUIRED',
...     ca_certs=certifi.where())

If you do not wish to use pyOpenSSL, you can simply omit the call to

<span class="pre">urllib3.contrib.pyopenssl.inject_into_urllib3()</span>

. urllib3 will fall back to the standard-library 

<span class="pre">ssl</span>

 module. You may experience several warnings when doing this.

Warning

If you do not use pyOpenSSL, Python must be compiled with ssl support for certificate verification to work. It is uncommon, but it is possible to compile Python without SSL support. See this Stackoverflow thread for more details.

If you are on Google App Engine, you must explicitly enable SSL support in your 

<span class="pre">app.yaml</span>

:

libraries:
- name: ssl
  version: latest

Using timeouts

Timeouts allow you to control how long requests are allowed to run before being aborted. In simple cases, you can specify a timeout as a 

<span class="pre">float</span>

 to 

<span class="pre">request()</span>

:

>>> http.request(
...     'GET', 'http://httpbin.org/delay/3', timeout=4.0)
<urllib3.response.HTTPResponse>
>>> http.request(
...     'GET', 'http://httpbin.org/delay/3', timeout=2.5)
MaxRetryError caused by ReadTimeoutError

For more granular control you can use a 

<span class="pre">Timeout</span>

 instance which lets you specify separate connect and read timeouts:

>>> http.request(
...     'GET',
...     'http://httpbin.org/delay/3',
...     timeout=urllib3.Timeout(connect=1.0))
<urllib3.response.HTTPResponse>
>>> http.request(
...     'GET',
...     'http://httpbin.org/delay/3',
...     timeout=urllib3.Timeout(connect=1.0, read=2.0))
MaxRetryError caused by ReadTimeoutError

If you want all requests to be subject to the same timeout, you can specify the timeout at the 

<span class="pre">PoolManager</span>

 level:

>>> http = urllib3.PoolManager(timeout=3.0)
>>> http = urllib3.PoolManager(
...     timeout=urllib3.Timeout(connect=1.0, read=2.0))

You still override this pool-level timeout by specifying 

<span class="pre">timeout</span>

 to 

<span class="pre">request()</span>

.

Retrying requests

urllib3 can automatically retry idempotent requests. This same mechanism also handles redirects. You can control the retries using the 

<span class="pre">retries</span>

 parameter to 

<span class="pre">request()</span>

. By default, urllib3 will retry requests 3 times and follow up to 3 redirects.

To change the number of retries just specify an integer:

>>> http.requests('GET', 'http://httpbin.org/ip', retries=10)

To disable all retry and redirect logic specify 

<span class="pre">retries=False</span>

:

>>> http.request(
...     'GET', 'http://nxdomain.example.com', retries=False)
NewConnectionError
>>> r = http.request(
...     'GET', 'http://httpbin.org/redirect/1', retries=False)
>>> r.status
302

To disable redirects but keep the retrying logic, specify 

<span class="pre">redirect=False</span>

:

>>> r = http.request(
...     'GET', 'http://httpbin.org/redirect/1', redirect=False)
>>> r.status
302

For more granular control you can use a 

<span class="pre">Retry</span>

 instance. This class allows you far greater control of how requests are retried.

For example, to do a total of 3 retries, but limit to only 2 redirects:

>>> http.request(
...     'GET',
...     'http://httpbin.org/redirect/3',
...     retries=urllib3.Retry(3, redirect=2))
MaxRetryError

You can also disable exceptions for too many redirects and just return the 

<span class="pre">302</span>

response:

>>> r = http.request(
...     'GET',
...     'http://httpbin.org/redirect/3',
...     retries=urllib3.Retry(
...         redirect=2, raise_on_redirect=False))
>>> r.status
302

If you want all requests to be subject to the same retry policy, you can specify the retry at the 

<span class="pre">PoolManager</span>

 level:

>>> http = urllib3.PoolManager(retries=False)
>>> http = urllib3.PoolManager(
...     retries=urllib3.Retry(5, redirect=2))

You still override this pool-level retry policy by specifying 

<span class="pre">retries</span>

 to 

<span class="pre">request()</span>

.

Errors & Exceptions

urllib3 wraps lower-level exceptions, for example:

>>> try:
...     http.request('GET', 'nx.example.com', retries=False)
>>> except urllib3.exceptions.NewConnectionError:
...     print('Connection failed.')

See 

<span class="pre">exceptions</span>

 for the full list of all exceptions.

Logging

If you are using the standard library 

<span class="pre">logging</span>

 module urllib3 will emit several logs. In some cases this can be undesirable. You can use the standard logger interface to change the log level for urllib3’s logger:

>>> logging.getLogger("urllib3").setLevel(logging.WARNING)