python工具库介绍-requests：人性化的HTTP

Requests是Python基于Apache2 Licensed许可证的人性化HTTP库。

Python标准库中urllib2提供了不少HTTP 功能，但API不系统。它有点过时，完成最简单的任务也需要大量工作。

下面我们用实例演示访问github。

>>> import requests
>>> r = requests.get('https://api.github.com/user', auth=('ouyangchongwu@test.com', 'password'))
>>> r.status_code
200
>>> r.headers['content-type']
'application/json; charset=utf-8'
>>> r.encoding
'utf-8'
>>> r.text
u'{"login":"oychw",...}'
>>> r.json()
{u'disk_usage': 176, u'private_gists': 0, ...}

Requests为Python处理了所有HTTP/1.1操作，与Web服务的无缝集成。不需要为URL手动添加查询字符串或POST数据进行表单处理。基于urllib3, 能自动处理Keep-alive和HTTP连接池。

特点：

国际化域名和 URLs
Keep-Alive & 连接池
持久的 Cookie 会话
类浏览器的SSL认证
基本/摘要式的身份认证
优雅的键/值 Cookie
自动解压
Unicode响应体
多段文件上传
连接超时
支持 .netrc
适用于 Python 2.6—3.4
线程安全

用户手册

简介

Requests关注PEP 20的部分：

Beautiful is better than ugly.(美丽优于丑陋)
Explicit is better than implicit.(明确优于含糊)
Simple is better than complex.(简单优于复杂)
Complex is better than complicated.(复杂优于繁琐)
Readability counts.(可读性)

安装

安装：推荐：pip install requests，其次：easy_install requests
最新代码：
git clone git://github.com/kennethreitz/requests.git
下载tar.gz包：curl -OL https://github.com/kennethreitz/requests/tarball/master
下载zip包：curl -OL https://github.com/kennethreitz/requests/zipball/master
源码安装：python setup.py install

快速入门

发送请求：

下面获取Github的公共时间线，并在httpbin演示其他HTTP操作：

>>> import requests
>>> r = requests.get('https://github.com/timeline.json')
>>> r = requests.post("http://httpbin.org/post")
>>> r = requests.put("http://httpbin.org/put")
>>> r = requests.delete("http://httpbin.org/delete")
>>> r = requests.head("http://httpbin.org/get")
>>> r = requests.options("http://httpbin.org/get")

在URL中传递参数

URL的查询字符串(query string)例如， httpbin.org/get?key=val，在Requests可以用字典的形式构建。比如传递key1=value1和key2=value2到 httpbin.org/get:

>>> import requests
>>> payload = {'key1': 'value1', 'key2': 'value2'}
>>> r = requests.get("http://httpbin.org/get", params=payload)
>>> print(r.url)
http://httpbin.org/get?key2=value2&key1=value1
>>> payload = {'key1': 'value1', 'key2[]': ['value2', 'value3']}
>>> r = requests.get("http://httpbin.org/get", params=payload)
>>> print(r.url)
http://httpbin.org/get?key1=value1&key2%5B%5D=value2&key2%5B%5D=value3

注意字典里值为None的键会忽略。上面第２个例子访问的是http://httpbin.org/get?key1=value1&key2[]=value2&key2[]=value3 。注意key后面需要添加中括号对。

响应

>>> import requests
>>> r = requests.get('https://api.github.com/events')
>>> r.text
>>> u'[{"id":"2636319727","type":"PullRequestReviewCommentEvent","actor":{"id":1148601,"login":"i ...}]
>>> r.encoding
'utf-8'
>>> r.encoding = 'ISO-8859-1'

Requests会自动解码服务器的返回。大多数unicode字符集都能无缝解码。请求发出时Requests会基于响应的HTTP头部推测响应的编码。同时还可以设置和查询编码。改变编码后，访问 r.text 将会使用 r.encoding 。

二进制响应

r.content可以以字节的方式显示响应。

>>> r.content
b'[{"repository":{"open_issues":0,"url":"https://github.com/...

传输格式gzip和deflate会自动转码。处理图片实例：

>>> from PIL import Image
>>> from StringIO import StringIO
>>> i = Image.open(StringIO(r.content))

Json响应

Requests内置了JSON解码器:

>>> import requests
>>> r = requests.get('https://github.com/timeline.json')
>>> r.json()
{u'documentation_url': u'https://developer.github.com/v3/activity/events/#list-public-events', u'message': u"Hello there, wayfaring stranger. If you're reading this then you probably didn't see our blog post a couple of years back announcing that this API would go away: http://git.io/17AROg Fear not, you should be able to get what you need from the shiny new Events API instead."}

JSON解码失败时r.json 就会抛出异常。例如， 401 (Unauthorized) ， ValueError: No JSON object could be decoded等。

原始响应

极端的情况下需要查看服务器的原始套接字响应，请求时设置 stream=True：

>>> import requests
>>> r = requests.get('https://api.github.com/events', stream=True)
>>> r.raw
<urllib3.response.HTTPResponse object at 0x7f807dd6f4d0>
>>> r.raw.read(10)
'\x1f\x8b\x08\x00\x00\x00\x00\x00\x00\x03'

通常需要存为文件:

with open(filename, 'wb') as fd:
    for chunk in r.iter_content(chunk_size):
        fd.write(chunk)

Response.iter_content 能减少直接使用Response.raw的大量处理，下载流时尤其推荐。

自定义头

>>> import requests
>>> import json
>>> url = 'https://api.github.com/some/endpoint'
>>> payload = {'some': 'data'}
>>> headers = {'content-type': 'application/json'}
>>> r = requests.post(url, data=json.dumps(payload), headers=headers)

更加复杂的POST请求

表单直接以字典形式发送：

>>> import requests
>>> payload = {'key1': 'value1', 'key2': 'value2'}
>>> r = requests.post("http://httpbin.org/post", data=payload)
>>> print(r.text)
{
  "args": {}, 
  "data": "", 
  "files": {}, 
  "form": {
    "key1": "value1", 
    "key2": "value2"
  }, 
  "headers": {
    "Accept": "*/*", 
    "Accept-Encoding": "gzip, deflate, compress", 
    "Content-Length": "23", 
    "Content-Type": "application/x-www-form-urlencoded", 
    "Host": "httpbin.org", 
    "User-Agent": "python-requests/2.2.1 CPython/2.7.6 Linux/3.13.0-53-generic"
  }, 
  "json": null, 
  "origin": "119.122.150.177", 
  "url": "http://httpbin.org/post"
}

string则会被直接发布出去。Github API v3中接受编码为JSON的POST/PATCH数据

>>> import requests
>>> import json
>>> url = 'https://api.github.com/some/endpoint'
>>> payload = {'some': 'data'}
>>> r = requests.post(url, data=json.dumps(payload))

POST复杂编码的文件

>>> import requests
>>> url = 'http://httpbin.org/post'
>>> files = {'file': open('/home/andrew/test.xls', 'rb')}
>>>  r = requests.post(url, files=files)
>>> url = 'http://httpbin.org/post'
>>> r.text
u'{\n  "args": {}, \n  "data": "", \n  "files": {\n ...  "url": "http://httpbin.org/post"\n}\n'

可以显式地设置文件名，文件类型和请求头:

>>> import requests
>>> files = {'file': ('report.xls', open('/home/andrew/test.xls', 'rb'), 'application/vnd.ms-excel', {'Expires': '0'})}
>>> url = 'http://httpbin.org/post'
>>> r = requests.post(url, files=files)
>>> r.text
u'{\n  "args": {}, \n  "data": ""..."url": "http://httpbin.org/post"\n}\n'

还可以直接用文字代替文件：

>>> import requests
>>> url = 'http://httpbin.org/post'
>>> files = {'file': ('report.csv', 'some,data,to,send\nanother,row,to,send\n')}
>>> r = requests.post(url, files=files)
>>> r.text
u'{\n  "args": {}, \n  "data": "", \n  "files": {\n  ...  "json": null, \n  "origin": "14.153.22.104", \n  "url": "http://httpbin.org/post"\n}\n'

multipart/form-data不支持特别大的文件，建议使用requests-toolbelt，参考：toolbelt

响应状态码

>>> import requests
>>> r = requests.get('http://httpbin.org/get')
>>> r.status_code
200
>>> r.status_code == requests.codes.ok
True
>>> bad_r = requests.get('http://httpbin.org/status/404')
>>> bad_r.status_code
404
>>> bad_r.raise_for_status()
>>> r.raise_for_status()

上面的requests.codes.ok是内置的状态码查询对象。可以使用 Response.raise_for_status()跑出失败请求(4XX客户端错误或5XX服务器异常)，我们可以通过 Response.raise_for_status() 来抛出异常。r的返回为200，所以返回None，不产生异常。

响应头

>>> r.headers
{'content-length': '275', 'server': 'nginx', 'connection': 'keep-alive', 'access-control-allow-credentials': 'true', 'date': 'Tue, 10 Mar 2015 08:21:36 GMT', 'access-control-allow-origin': '*', 'content-type': 'application/json'}

>>> r.headers['Content-Type']
'application/json'

>>> r.headers.get('content-type')
 'application/json'

根据 RFC 2616，HTTP头部不区分大小写。根据RFC 7230，接收方会对服务端对同一key的不同value进行组合。

可以访问响应中包含的Cookie:

>>> import requests
>>> url = 'http://automationtesting.sinaapp.com/login'
>>> r = requests.get(url)
>>> r.cookies.keys()
['saeut', 'trac_form_token', 'trac_session']
>>> r.cookies['saeut']
 'CkMPGlT+tfQiXS9uGYviAg=='

使用cookies参数可以发送你的cookies到服务器:

>>> import requests
>>> url = 'http://httpbin.org/cookies'
>>> cookies = dict(cookies_are='working')
>>> r = requests.get(url, cookies=cookies)
>>> r.text
u'{\n  "cookies": {\n    "cookies_are": "working"\n  }\n}\n'

重定向与请求历史

默认对HEAD以外其他所有动作进行位置重定向。Response.history可以看到重定向的记录。

>>> import requests
>>> r = requests.get('http://github.com')
>>> r.url
u'https://github.com/'
>>> r.status_code
200
>>> r.history
[<Response [301]>]

GET, OPTIONS, POST, PUT, PATCH 或者 DELETE可以通过allow_redirects参数禁用重定向，这个设置对HEAD也生效:

>>> import requests
>>> r = requests.get('http://github.com', allow_redirects=False)
>>> r.status_code
301
>>> r.history
[]
>>> r = requests.head('http://github.com', allow_redirects=True)
>>> r.url
u'https://github.com/'
>>> r.history
[<Response [301]>]

超时

超时告诉requests在经过timeout参数的秒之后停止等待响应:

>>> import requests
>>> requests.get('http://github.com', timeout=0.1)    
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/dist-packages/requests/api.py", line 55, in get
    return request('get', url, **kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/api.py", line 44, in request
    return session.request(method=method, url=url, **kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/sessions.py", line 455, in request
    resp = self.send(prep, **send_kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/sessions.py", line 558, in send
    r = adapter.send(request, **kwargs)
  File "/usr/lib/python2.7/dist-packages/requests/adapters.py", line 387, in send
    raise Timeout(e)
requests.exceptions.Timeout: (<urllib3.connectionpool.HTTPConnectionPool object at 0x7f807dd6f050>, 'Connection to github.com timed out. (connect timeout=0.1)')
>>>

注: 超时不是对整个响应下载的时间限制, 而且指定时间没有收到服务器返回就抛出异常。

错误与异常

ConnectionError：网络问题(如DNS失败、拒绝连接等)。

HTTPError: 比较罕见的无效HTTP响应时。

Timeout：请求超时。

TooManyRedirects：超过了设定的最大重定向次数。

requests.exceptions.RequestException是所有具体异常的基类。

高级用法

Session对象

Session对象能够跨请求保持参数，Session实例发出的所有请求共享cookies。

Session对象具有主Requests API的所有方法。

>>> s = requests.Session()
>>> s.get('http://httpbin.org/cookies/set/sessioncookie/123456789')
<Response [200]>
>>> r = s.get("http://httpbin.org/cookies")
>>> print(r.text)
{
  "cookies": {
    "sessioncookie": "123456789"
  }
}

Session也可为request方法提供缺省数据，添加属性即可:

>>> import requests
>>> s = requests.Session()
>>> s.auth = ('user', 'pass')
>>> s.headers.update({'x-test': 'true'})
>>> s.get('http://httpbin.org/headers', headers={'x-test2': 'true'})
<Response [200]>

传递给request方法的字典都会与已有session层的值合并。方法层的参数会覆盖会话的参数。在方法层参数中将键值设置为None，会被自动忽略key。参考： session api

请求(Request)和响应(Response)对象

requests.get()等请求主要做两件的事情。一为构建Request 对象。二为收到服务器响应时产生Response 对象。Response对象包含服务器返回和原来的 Request 对象。

>>> import requests
>>> r = requests.get('http://en.wikipedia.org/wiki/Monty_Python')
>>> r.headers
{'content-length': '67559', ...}
>>> r.request.headers
{'Connection': 'keep-alive', 'Accept-Encoding': ...}

预请求

当从API或会话调用接收Response对象时，request属性实际上是PreparedRequest。如果你需要修改body或header，可以如下方式进行处理：

from requests import Request, Session

s = Session()
req = Request('GET', url,
    data=data,
    headers=header
)
prepped = req.prepare()

# do something with prepped.body
# do something with prepped.headers

resp = s.send(prepped,
    stream=stream,
    verify=verify,
    proxies=proxies,
    cert=cert,
    timeout=timeout
)

print(resp.status_code)

这里没有对Request对象进行特殊处理，而是修改PreparedRequest对象。然后用requests.* 或Session.*.发送。

上述代码没有Request Session。Session层状态，如cookie不会使用。用Session.prepare_request()替换Request.prepare()即可增加状态支持：

from requests import Request, Session

s = Session()
req = Request('GET',  url,
    data=data
    headers=headers
)

prepped = s.prepare_request(req)

# do something with prepped.body
# do something with prepped.headers

resp = s.send(prepped,
    stream=stream,
    verify=verify,
    proxies=proxies,
    cert=cert,
    timeout=timeout
)

print(resp.status_code)

SSL证书验证

使用 verify 参数可以像web浏览器一样为HTTPS请求验证SSL证书:

参考资料

讨论qq群144081101 591302926 567351477
requests英文文档
requests-docs-cn.readthedocs.org
docs.python-requests.org/en/latest/
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用户手册

简介

安装

快速入门

高级用法

参考资料

links