1.'content-type':'application/x-www-form-urlencoded'

• data参数提交<str>文本或<dict>字典都可以
• headers为空时，data提交content-type默认也是application/x-www-form-urlencoded

requests.post(url,headers={'content-type':'application/x-www-form-urlencoded'},data='f=10') 

requests.post(url,headers={'content-type':'application/x-www-form-urlencoded'},data={'f':10}) 

2.'content-type':'application/json'

• data参数提交<str>或json参数提交<dict>
• data参数提交<str>：注意str必须是json.dumps(<dict>)转换的标准的json字符串，而非str(<dict>)，这两者并不完全等同。
• json参数提交<dict>：模块会自动将dict转换为json提交。

requests.post(url,headers={'content-type':'application/json'},data=json.dumps({'f':10}))

requests.post(url,headers={'content-type':'application/json'},json={'f':10}) 

3.'content-type':'text/xml'

• data参数提交<bytes>
• 通常用于上传xml格式文本等；将文本<str>.encode("utf-8")编码为bytes类型上传

requests.post(url,headers={'content-type':'text/xml'},data='<xml......>'.encode("utf-8"))

4.'content-type':'multipart/formdata'

• files参数提交<dict>
• 用于上传文件；通常Content-Type中除了Content-Type: multipart/form-data，还有个boundary=随机字符串，该项的作用是当作提交内容的分隔符，构造files时用不到可以忽略。

举个例子：

Request Headers
    Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryzf3ou2ZJHNJq9V0N
------------------------------------------------------------
FormData
    file: (binary)
    else1: xxx1
    else2: xxx2
------------------------------------------------------------
FormData    view source
    ------WebKitFormBoundaryzf3ou2ZJHNJq9V0N
    Content-Disposition: form-data; name="file"; filename="test.jpg"
    Content-Type: image/jpeg


    ------WebKitFormBoundaryzf3ou2ZJHNJq9V0N
    Content-Disposition: form-data; name="else1"

    xxx1
    ------WebKitFormBoundaryzf3ou2ZJHNJq9V0N
    Content-Disposition: form-data; name="else2"

    xxx2
    ------WebKitFormBoundaryzf3ou2ZJHNJq9V0N--

可以整理如下方式提交

files = {
        "file":("test.jpg", open(r"D:\test\test.jpg",'rb')),
        "else1": (None,"xxx1"),
        "else2": (None,"xxx2")
    }
r = requests.post(url,files=files)