首先是統一編碼。
這個模組實現了requests的api。
從本模組下倒入sessions，主要的實現都是sessions裡面實現，其他的檔案都是helper。這個也依賴urllib3等

# -*- coding: utf-8 -*-

"""
requests.api
~~~~~~~~~~~~

This module implements the Requests API.

:copyright: (c) 2012 by Kenneth Reitz.
:license: Apache2, see LICENSE for more details.
"""

from . import sessions
 

 首先是request方法，也是其他方法的基本方法。
method  ，get,post,delete等等。
url    將要訪問的url地址
**kwargs    其他引數

常用引數  

param，請求的連結太長了，可以通過存入param中。
data, 這個用來儲存表單資料，和上面的區別就是，不顯示在瀏覽器的導航欄。
headers，請求頭，在瀏覽器開發者模式下的network欄裡面可以看到動態請求。
cookies，可以在headers裡面設定，也可以自己更明確的新增。
auth  ，授權，在一些地方可以用到。
timeout，設定連線和響應超時時長
proxy，代理，特別是那種喜歡拉黑人家ip的網站，可以用代理進行避免。
stream，下載檔案，不想一直阻塞。中間想要觀察資料動向可以使用。
下面是具體的格式。

#: A case-insensitive dictionary of headers to be sent on each
        #: :class:`Request <Request>` sent from this
        #: :class:`Session <Session>`.
        self.headers = default_headers()

        #: Default Authentication tuple or object to attach to
        #: :class:`Request <Request>`.
        self.auth = None

        #: Dictionary mapping protocol or protocol and host to the URL of the proxy
        #: (e.g. {'http': 'foo.bar:3128', 'http://host.name': 'foo.bar:4012'}) to
        #: be used on each :class:`Request <Request>`.
        self.proxies = {}

        #: Event-handling hooks.
        self.hooks = default_hooks()

        #: Dictionary of querystring data to attach to each
        #: :class:`Request <Request>`. The dictionary values may be lists for
        #: representing multivalued query parameters.
        self.params = {}

        #: Stream response content default.
        self.stream = False

        #: SSL Verification default.
        self.verify = True

        #: SSL client certificate default, if String, path to ssl client
        #: cert file (.pem). If Tuple, ('cert', 'key') pair.
        self.cert = None

        #: Maximum number of redirects allowed. If the request exceeds this
        #: limit, a :class:`TooManyRedirects` exception is raised.
        #: This defaults to requests.models.DEFAULT_REDIRECT_LIMIT, which is
        #: 30.
        self.max_redirects = DEFAULT_REDIRECT_LIMIT

        #: Trust environment settings for proxy configuration, default
        #: authentication and similar.
        self.trust_env = True

        #: A CookieJar containing all currently outstanding cookies set on this
        #: session. By default it is a
        #: :class:`RequestsCookieJar <requests.cookies.RequestsCookieJar>`, but
        #: may be any other ``cookielib.CookieJar`` compatible object.
        self.cookies = cookiejar_from_dict({})

        # Default connection adapters.
        self.adapters = OrderedDict()
        self.mount('https://', HTTPAdapter())
        self.mount('http://', HTTPAdapter())
 

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

    :param method: method for the new :class:`Request` object.
    method用於將要建立的類Requet的引數
    :param url: URL for the new :class:`Request` object.
    傳入Request的URL引數


    :param params: (optional) Dictionary, list of tuples or bytes to send
        in the body of the :class:`Request`.
    字典型別或者是tuple集合或者byte型別
    params是引數，也就是  ?key=value&key=value&...
    也可以通過 [(key,value)] 也可以是直接按照http協議編碼好的資料


    :param data: (optional) Dictionary, list of tuples, bytes, or file-like
        object to send in the body of the :class:`Request`.
    data 字典型別或者是tuple集合或者byte型別或者是一個檔案一樣的類 
    

    :param json: (optional) A JSON serializable Python object to send in the body of the     
    :class:`Request`.
    json，序列化傳送過去的資料


    :param headers: (optional) Dictionary of HTTP Headers to send with the 
    :class:`Request`.
    請求頭，包括許多的格式和標準還有引數資訊等等。字典或者http Headers


    :param cookies: (optional) Dict or CookieJar object to send with the 
    :class:`Request`.
    cookies可以放入headers中也可以手動新增。可以是字典，cookiejar物件


    :param files: (optional) Dictionary of ``'name': file-like-objects`` (or ``{'name': 
    file-tuple}``) for multipart encoding upload.
    字典或者多個傳輸模組的方式。
        ``file-tuple`` can be a 2-tuple ``('filename', fileobj)``, 3-tuple ``('filename', 
    fileobj, 'content_type')``
    file-tuple可以是兩個元素或者是三個元素的元組，或者是四個元素的元組
        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.
    授權


    :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
    設定超時，等待伺服器多少秒後就放棄傳送。可以是float或者是一個元組，分別是連線和響應超時時長


    :param allow_redirects: (optional) Boolean. Enable/disable 
    GET/OPTIONS/POST/PUT/PATCH/DELETE/HEAD redirection. Defaults to ``True``.
    :type allow_redirects: bool
     傳入一個bool值，表示是否允許重定向。

    :param proxies: (optional) Dictionary mapping protocol to the URL of the proxy.
    代理，可以設定多個代理。


    :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``.
    如果是一個bool值就是控制是否給證書，如果是一個字串就是整數存放的位置。預設是True。


    :param stream: (optional) if ``False``, the response content will be immediately 
    downloaded.
    是按照stream還是直接下載，預設是直接下載，如果我們下載檔案，視訊什麼的可以通過流下載。
    我們可以看一下you-get


    :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.
    # 通過with模式我們可以保證session會被關閉。避免離開sockets導致了錯誤，比如其他地方記憶體益處。
    with sessions.Session() as session:
        return session.request(method=method, url=url, **kwargs)

    

def get(url, params=None, **kwargs):
    r"""Sends a GET request.

    :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 \*\*kwargs: Optional arguments that ``request`` takes.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response
    """

    kwargs.setdefault('allow_redirects', True)
    return request('get', url, params=params, **kwargs)


def options(url, **kwargs):
    r"""Sends an OPTIONS request.

    :param url: URL for the new :class:`Request` object.
    :param \*\*kwargs: Optional arguments that ``request`` takes.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response
    """

    kwargs.setdefault('allow_redirects', True)
    return request('options', url, **kwargs)


def head(url, **kwargs):
    r"""Sends a HEAD request.

    :param url: URL for the new :class:`Request` object.
    :param \*\*kwargs: Optional arguments that ``request`` takes.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response
    """

    kwargs.setdefault('allow_redirects', False)
    return request('head', url, **kwargs)


def post(url, data=None, json=None, **kwargs):
    r"""Sends a POST request.

    :param url: URL for the new :class:`Request` object.
    :param data: (optional) Dictionary, list of tuples, bytes, or file-like
        object to send in the body of the :class:`Request`.
    :param json: (optional) json data to send in the body of the :class:`Request`.
    :param \*\*kwargs: Optional arguments that ``request`` takes.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response
    """

    return request('post', url, data=data, json=json, **kwargs)


def put(url, data=None, **kwargs):
    r"""Sends a PUT request.

    :param url: URL for the new :class:`Request` object.
    :param data: (optional) Dictionary, list of tuples, bytes, or file-like
        object to send in the body of the :class:`Request`.
    :param json: (optional) json data to send in the body of the :class:`Request`.
    :param \*\*kwargs: Optional arguments that ``request`` takes.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response
    """

    return request('put', url, data=data, **kwargs)


def patch(url, data=None, **kwargs):
    r"""Sends a PATCH request.

    :param url: URL for the new :class:`Request` object.
    :param data: (optional) Dictionary, list of tuples, bytes, or file-like
        object to send in the body of the :class:`Request`.
    :param json: (optional) json data to send in the body of the :class:`Request`.
    :param \*\*kwargs: Optional arguments that ``request`` takes.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response
    """

    return request('patch', url, data=data, **kwargs)


def delete(url, **kwargs):
    r"""Sends a DELETE request.

    :param url: URL for the new :class:`Request` object.
    :param \*\*kwargs: Optional arguments that ``request`` takes.
    :return: :class:`Response <Response>` object
    :rtype: requests.Response
    """

    return request('delete', url, **kwargs)

其他的都是上層的高階方法呼叫request。