Python Requests 最详细教程！爬虫必会之！

requests 是Python中一个非常出名的库，它极大的简化了 Python中进行HTTP请求的流程，我们来看一个简单的例子：

In [1]: import requests

In [2]: requests.get("https://jiajunhuang.com")
Out[2]: <Response [200]>

只需要两行便可以发起一个HTTP请求，多么的简单。

针对HTTP协议的 GET , POST , PUT , DELETE 等方法， requests 分别有：

requests.get
requests.options
requests.head
requests.post
requests.put
requests.patch
requests.delete

等对应的方法，他们都是 requests.request 的便捷版，也就是说，调用 requests.get 其实相当于调用 requests.request("GET", xxx) 。

接下来我们看看 requests.request 都能接受哪些参数，这其实也就是上述对应的 get 等方法能传入的参数：

def request(method, url, **kwargs):
    """Constructs and sends a :class:`Request <Request>`.

    :param method: method for the new :class:`Request` object.
    :param url: URL for the new :class:`Request` object.
    :param params: (optional) Dictionary, list of tuples or bytes to send
        in the body of the :class:`Request`.
    :param data: (optional) Dictionary, list of tuples, bytes, or file-like
        object to send in the body of the :class:`Request`.
    :param json: (optional) A JSON serializable Python object to send in the body of the :class:`Request`.
    :param headers: (optional) Dictionary of HTTP Headers to send with the :class:`Request`.
    :param cookies: (optional) Dict or CookieJar object to send with the :class:`Request`.
    :param files: (optional) Dictionary of ``'name': file-like-objects`` (or ``{'name': file-tuple}``) for multipart encoding upload.
        ``file-tuple`` can be a 2-tuple ``('filename', fileobj)``, 3-tuple ``('filename', fileobj, 'content_type')``
        or a 4-tuple ``('filename', fileobj, 'content_type', custom_headers)``, where ``'content-type'`` is a string
        defining the content type of the given file and ``custom_headers`` a dict-like object containing additional headers
        to add for the file.
    :param auth: (optional) Auth tuple to enable Basic/Digest/Custom HTTP Auth.
    :param timeout: (optional) How many seconds to wait for the server to send data
        before giving up, as a float, or a :ref:`(connect timeout, read
        timeout) <timeouts>` tuple.
    :type timeout: float or tuple
    :param allow_redirects: (optional) Boolean. Enable/disable GET/OPTIONS/POST/PUT/PATCH/DELETE/HEAD redirection. Defaults to ``True``.
    :type allow_redirects: bool
    :param proxies: (optional) Dictionary mapping protocol to the URL of the proxy.
    :param verify: (optional) Either a boolean, in which case it controls whether we verify
            the server's TLS certificate, or a string, in which case it must be a path
            to a CA bundle to use. Defaults to ``True``.
    :param stream: (optional) if ``False``, the response content will be immediately downloaded.
    :param cert: (optional) if String, path to ssl client cert file (.pem). If Tuple, ('cert', 'key') pair.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response

    Usage::

      >>> import requests
      >>> req = requests.request('GET', 'https://httpbin.org/get')
      <Response [200]>
    """

    # By using the 'with' statement we are sure the session is closed, thus we
    # avoid leaving sockets open which can trigger a ResourceWarning in some
    # cases, and look like a memory leak in others.
    with sessions.Session() as session:
        return session.request(method=method, url=url, **kwargs)

我们来看看这些便捷函数的参数:

• 第一个参数都是 url ，这就是要请求的 url ，例如 https://jiajunhuang.com ，是必填的。
• 参数 params 是query string，它可以是一个字典，或者一个list，list的内容是一堆的tuple，也可以是bytes。
• 参数 data 是 HTTP 请求中的 body ，它可以是一个字典，或者一个list，list的内容是一堆的tuple，也可以是bytes或者文件
• 参数 json 是为了方便请求而提供的参数，它其实相当于 data ，但是会自动把请求的 Content-Type 设置为 application/json
• 参数 headers 是 HTTP 请求中的头部，它是一个字典
• 参数 cookies 是所携带的 Cookie ，它可以是一个字典或者 CookieJar 的实例
• 参数 files 是要上传的文件，它可以是一个字典，字典的内容是tuple
• 参数 auth 用于开启 HTTP 请求的认证
• 参数 timeout 是超时时间
• 参数 allow_redirects 是否允许重定向，它是一个布尔值
• 参数 proxies 是是否使用代理
• 参数 verify 是否检查服务端的证书，传布尔值或者 CA 的路径
• 参数 stream 是布尔值，代表是否以流的方式读取结果
• 参数 cert 传入客户端的SSL证书

而 requests 中， HTTP 请求的返回结果是 Response 的实例，包括方法：

• json 用于把返回结果自动转换成 JSON
• ok 用于检查返回的状态码是否是 400 以下，注意，ok是一个property
• text 用于以文本方式输出返回结果，注意，text是一个 property

因此，我们可以看看常见的两种用法，一种是请求接口并且转换成 JSON :

import requests

resp = requests.get("https://api.jiajunhuang.com/v1/ip")
print(resp.json())

另外一种是打印状态码并且打印出响应结果：

import requests

resp = requests.get("https://api.jiajunhuang.com/v1/ip")
print(resp.status_code)
print(resp.text)