Why can't my code get the data returned by the API? How to solve this problem?

Troubleshooting and solving the problem that Python code cannot obtain the data returned by API

This article analyzes a Python code case that returns empty values ​​when calling ip-api.com API using the requests library and provides a solution.

Problem description

The following code tries to get the batch IP information of ip-api.com using a POST request, but always returns a null value:

 import random, requests, json

ip = [
  "49.104.25.257",
  "39.115.131.116"
]

api = "http://ip-api.com/batch?fields=58898?lang=zh_cn"
headers = {
    "user-agent": "mozilla/5.0 (windows nt 10.0; win64; x64) applewebkit/537.36 (khtml, like gecko) chrome/119.0.0.0 safari/537.36 edg/119.0.0.0",
    "content-type":"application/json"
    }

ip = json.dumps(ip, ensure_ascii=False, indent=2)
print(ip)

resp = requests.post(url=api,data=ip,headers=headers)
print(resp.status_code)
print(resp.text)

resp.close()

This API is a free version with a limit of 45 requests per minute, using POST requests, fields=58898 is used to specify the return field. Although there is no problem in querying the IP directly on the API website, the code always returns a null value and requests library does not report an error.

Problem analysis and solutions

After carefully checking the code and API documentation, I found that the problem is the query parameter settings of the URL. In the original code, the URL is:

 api = "http://ip-api.com/batch?fields=58898?lang=zh_cn"

& connection should be used between multiple query parameters, rather than continuous use ? The correct URL should be:

 api = "http://ip-api.com/batch?fields=58898&lang=zh_CN"

In addition, it is recommended to set the lang parameter to zh_CN to ensure that Chinese data is returned. At the same time, User-Agent and content-type in HTTP Header should use the standard naming method, with the initials capitalized.

Here is the modified complete code:

 import requests
import json

ip = [
    "49.104.25.257",
    "39.115.131.116"
]

api = "http://ip-api.com/batch?fields=58898&lang=zh_CN"
headers = {
    "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/119.0.0.0 Safari/537.36 Edg/119.0.0.0",
    "Content-Type": "application/json"
}

ip = json.dumps(ip, ensure_ascii=False, indent=2)
print(ip)

resp = requests.post(url=api, data=ip, headers=headers)
print(resp.status_code)
print(resp.text)

resp.close()

By modifying the URL and HTTP Header, the API returns data can be successfully obtained. This example illustrates the potential failure of a subtle syntax error in API calls, emphasizing the importance of double-checking URLs and parameters.

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