使用requests发送post请求
先来看看使用requests来发送post请求是多少好用，发送请求
Requests 简便的 API 意味着所有 HTTP 请求类型都是显而易见的。例如，你可以这样发送一个 HTTP POST 请求：
>>>r = requests.post('http://httpbin.org/post', data = {'key':'value'}) 使用data可以传递字典作为参数，同时也可以传递元祖
>>>payload = (('key1', 'value1'), ('key1', 'value2'))>>>r = requests.post('http://httpbin.org/post', data=payload)>>>print(r.text){ ... "form": { "key1": [ "value1", "value2" ] }, ...} 传递json是这样
>>>import json>>>url = 'https://api.github.com/some/endpoint'>>>payload = {'some': 'data'}>>>r = requests.post(url, data=json.dumps(payload)) 2.4.2 版的新加功能：
>>>url = 'https://api.github.com/some/endpoint'>>>payload = {'some': 'data'}>>>r = requests.post(url, json=payload) 也就是说，你不需要对参数做什么变化，只需要关注使用data=还是json=，其余的requests都已经帮你做好了。
使用scrapy发送post请求
通过源码可知scrapy默认发送的get请求，当我们需要发送携带参数的请求或登录时，是需要post、请求的，以下面为例
from scrapy.spider import CrawlSpiderfrom scrapy.selector import Selectorimport scrapyimport jsonclass LaGou(CrawlSpider): name = 'myspider' def start_requests(self): yield scrapy.FormRequest( url='https://www.******.com/jobs/positionAjax.json?city=%E5%B9%BF%E5%B7%9E&needAddtionalResult=false', formdata={ 'first': 'true',#这里不能给bool类型的True，requests模块中可以 'pn': '1',#这里不能给int类型的1，requests模块中可以 'kd': 'python' },这里的formdata相当于requ模块中的data，key和value只能是键值对形式 callback=self.parse ) def parse(self, response): datas=json.loads(response.body.decode())['content']['positionResult']['result'] for data in datas: print(data['companyFullName'] + str(data['positionId'])) 官方推荐的 Using FormRequest to send data via HTTP POST
return [FormRequest(url="http://www.example.com/post/action", formdata={'name': 'John Doe', 'age': '27'}, callback=self.after_post)] 这里使用的是FormRequest，并使用formdata传递参数，看到这里也是一个字典。
但是，超级坑的一点来了，今天折腾了一下午，使用这种方法发送请求，怎么发都会出问题，返回的数据一直都不是我想要的
return scrapy.FormRequest(url, formdata=(payload))
在网上找了很久，最终找到一种方法，使用scrapy.Request发送请求，就可以正常的获取数据。
复制代码代码如下:
return scrapy.Request(url, body=json.dumps(payload), method='POST', headers={'Content-Type': 'application/json'},)
参考：Send Post Request in Scrapy
my_data = {'field1': 'value1', 'field2': 'value2'}request = scrapy.Request( url, method='POST', body=json.dumps(my_data), headers={'Content-Type':'application/json'} ) FormRequest 与 Request 区别
在文档中，几乎看不到差别，
The FormRequest class adds a new argument to the constructor. The remaining arguments are the same as for the Request class and are not documented here.
Parameters: formdata (dict or iterable of tuples) – is a dictionary (or iterable of (key, value) tuples) containing HTML Form data which will be url-encoded and assigned to the body of the request.
说FormRequest新增加了一个参数formdata，接受包含表单数据的字典或者可迭代的元组，并将其转化为请求的body。并且FormRequest是继承Request的
class FormRequest(Request): def __init__(self, *args, **kwargs): formdata = kwargs.pop('formdata', None) if formdata and kwargs.get('method') is None: kwargs['method'] = 'POST' super(FormRequest, self).__init__(*args, **kwargs) if formdata: items = formdata.items() if isinstance(formdata, dict) else formdata querystr = _urlencode(items, self.encoding) if self.method == 'POST': self.headers.setdefault(b'Content-Type', b'application/x-www-form-urlencoded') self._set_body(querystr) else: self._set_url(self.url + ('&' if '?' in self.url else '?') + querystr) ###def _urlencode(seq, enc): values = [(to_bytes(k, enc), to_bytes(v, enc)) for k, vs in seq for v in (vs if is_listlike(vs) else [vs])] return urlencode(values, doseq=1) 最终我们传递的{‘key': ‘value', ‘k': ‘v'}会被转化为'key=value&k=v' 并且默认的method是POST，再来看看Request
class Request(object_ref): def __init__(self, url, callback=None, method='GET', headers=None, body=None, cookies=None, meta=None, encoding='utf-8', priority=0, dont_filter=False, errback=None, flags=None): self._encoding = encoding # this one has to be set first self.method = str(method).upper()
默认的方法是GET，其实并不影响。仍然可以发送post请求。这让我想起来requests中的request用法，这是定义请求的基础方法。
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 or bytes to be sent in the query string for the :class:`Request`. :param data: (optional) Dictionary or list of tuples ``[(key, value)]`` (will be form-encoded), 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 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', 'http://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) 以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持VEVB武林网。
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