Can I post a .json file on github using python requests?

You can use Github create repo content API for creating a file on your repository via the API :

PUT /repos/:owner/:repo/contents/:path

You would need to create a personal access token first. For example :

import requests 
import base64

token = "YOUR_TOKEN"

repo = 'bertrandmartel/test-repo'
path = 'data.json'

data = open("data.json", "r").read()

r = requests.put(
    f'https://api.github.com/repos/{repo}/contents/{path}',
    headers = {
        'Authorization': f'Token {token}'
    },
    json = {
        "message": "add new file",
        "content": base64.b64encode(data.encode()).decode(),
        "branch": "master"
    }
)
print(r.status_code)
print(r.json())

You can also use PyGithub library :

from github import Github

token = "YOUR_TOKEN"

repo = "bertrandmartel/test-repo"
path = "data.json"

# if using username and password
#g = Github("user", "password")

g = Github(token)

data = open("data.json", "r").read()

repo = g.get_repo(repo)
repo.create_file(
    path = path, 
    message = "add new file", 
    content = data, 
    branch = "master"
)