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使用scrapy发送post请求的坑

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这是崔斯特的第六十三篇原创文章

使用scrapy发送post请求的坑

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:

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>>> 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

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>>> 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

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>>> 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:

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>>> 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

官方推荐的 Using FormRequest to send data via HTTP POST

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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

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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。

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return scrapy.Request(url, body=json.dumps(payload), method='POST', headers={'Content-Type': 'application/json'},)

参考:Send Post Request in Scrapy

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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

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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

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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。

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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)

本文标题:使用scrapy发送post请求的坑

文章作者:小歪

发布时间:2018年08月24日 - 21:08

最后更新:2018年09月03日 - 21:09

原始链接:https://zhangslob.github.io/2018/08/24/使用scrapy发送post请求的坑/

许可协议: 署名-非商业性使用-禁止演绎 4.0 国际 转载请保留原文链接及作者。

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