Python Requests调用API报400错误，http.client却可正常请求

我尝试调用一个私有API，请求内容已做模糊处理。该请求在Postman中能正常运行，但将Postman生成的代码复制到VS Code后无法工作：

import json
import requests

url = "https://myapi.com/v1/search"
payload = json.dumps({
    'username': 'user',
    'start_date' : '01/01/2023T16:06:40+00:00',
    'end_date' : '01/02/2023T16:06:40+00:00'
})
headers = {
    'Authorization': 'Bearer XXXX',
    'Content-Type': 'application/json'
}
response = requests.post(url, headers=headers, data=payload)
response.raise_for_status()
print(response.json())

错误信息：

response.raise_for_status()
  File "C:\Users\XXXX\AppData\Local\Programs\Python\Python39\lib\site-packages\requests\models.py", line 1021, in raise_for_status
    raise HTTPError(http_error_msg, response=self)
requests.exceptions.HTTPError: 400 Client Error:  for url: https://myapi.com/v1/search

但使用http.client库发起请求却能成功：

import json
import http.client

conn = http.client.HTTPSConnection("myapi.com")
payload = json.dumps({
    'username': 'user',
    'start_date' : '01/01/2023T16:06:40+00:00',
    'end_date' : '01/02/2023T16:06:40+00:00'
})
headers = {
    'Authorization': 'Bearer XXXX',
    'Content-Type': 'application/json'
}
conn.request("POST", "/v1/search", payload, headers)
res = conn.getresponse()
data = res.read()
print(res.getcode())
print(data.decode("utf-8"))

我已尝试以下方案，但问题依旧：

• 将payload传入request的json参数，即requests.post(url, headers=headers, json=payload)
• 在headers中添加{"User-Agent": "PostmanRuntime/7.30.0"}
• 在请求中加入verify=False
• 尝试使用requests.Session：

import json
import requests

s = requests.Session()
url = "https://myapi.com/v1/search"
s.headers = {
    'Authorization': 'Bearer XXXX',
    'Content-Type': 'application/json'
}
payload = json.dumps({
    'username': 'user',
    'start_date' : '01/01/2023T16:06:40+00:00',
    'end_date' : '01/02/2023T16:06:40+00:00'
})
response = s.post(url, data=payload)
response.raise_for_status()
print(response.json())

Python版本：3.9.7
Requests版本：2.28.1

希望能得到解决思路！

内容的提问来源于stack exchange，提问作者cozzymotto