使用python的requests库作一个登陆的post请求，代码如下：

import requests
import json

def login():
	url = ‘http://192.168.22.1:8090/login’
	pdata = {"userName": "lidaxia","password":"loginpsd"}
	res = requests.post(url,data = json.dumps(pdata))

在postman中，body使用json编码，可以发送成功，但是在python中一直因为请求体格式不对报错
后经过百度，将代码改成以下：

import requests

def login():
	url = ‘http://192.168.22.1:8090/login’
	pdata = {"userName": "lidaxia","password":"loginpsd"}
	res = requests.post(url,json = pdata)

问题解决！
认真了解了requests.post的几个参数，官方文档如下：

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More complicated POST requests
Typically, you want to send some form-encoded data — much like an HTML form. To do this, simply pass a dictionary to the data argument. Your dictionary of data will automatically be form-encoded when the request is made:

>>> payload = {'key1': 'value1', 'key2': 'value2'}

>>> r = requests.post("https://httpbin.org/post", data=payload)
>>> print(r.text)
{
  ...
  "form": {
    "key2": "value2",
    "key1": "value1"
  },
  ...
}

The data argument can also have multiple values for each key. This can be done by making data either a list of tuples or a dictionary with lists as values. This is particularly useful when the form has multiple elements that use the same key:

>>> payload_tuples = [('key1', 'value1'), ('key1', 'value2')]
>>> r1 = requests.post('https://httpbin.org/post', data=payload_tuples)
>>> payload_dict = {'key1': ['value1', 'value2']}
>>> r2 = requests.post('https://httpbin.org/post', data=payload_dict)
>>> print(r1.text)
{
  ...
  "form": {
    "key1": [
      "value1",
      "value2"
    ]
  },
  ...
}
>>> r1.text == r2.text
True

There are times that you may want to send data that is not form-encoded. If you pass in a string instead of a dict, that data will be posted directly.

For example, the GitHub API v3 accepts JSON-Encoded POST/PATCH data:

>>> import json

>>> url = 'https://api.github.com/some/endpoint'
>>> payload = {'some': 'data'}

>>> r = requests.post(url, data=json.dumps(payload))

Instead of encoding the dict yourself, you can also pass it directly using the json parameter (added in version 2.4.2) and it will be encoded automatically:

>>> url = 'https://api.github.com/some/endpoint'
>>> payload = {'some': 'data'}

>>> r = requests.post(url, json=payload)

Note, the json parameter is ignored if either data or files is passed.

Using the json parameter in the request will change the Content-Type in the header to application/json.

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看完官方文档， res = requests.post(url,data = dumps(pdata))和res = requests.post(url,json = pdata)的区别为，使用参数是json时会将请求中的Content-Type改成application/json，于是修改代码去验证：

import requests
import json

def login():
	url = ‘http://192.168.22.1:8090/login’
	pdata = {"userName": "lidaxia","password":"loginpsd"}
	headers = {"Content-Type":"application/json"}
	res = requests.post(url,data = json.dumps(pdata),headers = headers)

也没有问题，所以，综上所述，如果post请求体是json格式的，使用json参数会更简单，推荐使用！