执行Python程序无输出、黑屏问题求助（Android开发者）

Hey there! As someone who’s dabbled in both Android development and web scraping, let’s break down why your Python script is giving you a black screen with no output, and fix it step by step.

1. Missing User-Agent Header (Most Likely Culprit) #

Most government websites like parivahan block requests from the default requests library User-Agent—it’s a dead giveaway for bots. Let’s add a realistic browser UA to your requests to avoid being blocked:

import sys
import requests
from bs4 import BeautifulSoup, SoupStrainer

# Add a browser-like User-Agent
headers = {
    'User-Agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/118.0.0.0 Safari/537.36'
}

home_url = 'https://parivahan.gov.in/rcdlstatus/'
post_url = 'https://parivahan.gov.in/rcdlstatus/vahan/rcDlHome.xhtml'

# ... rest of your code ...

# Update GET request with headers
r = requests.get(url=home_url, headers=headers)

# ... rest of your code ...

# Update POST request with headers
r = requests.post(url=post_url, data=data, cookies=cookies, headers=headers)

2. Dynamic Form IDs (The Hardcoded j_idt32 Problem) #

JSF-based sites like parivahan generate dynamic IDs for form elements every time the page loads. Your hardcoded form_rcdl:j_idt32 might not match the current page’s ID. Let’s extract it dynamically:

# After parsing the initial GET response
submit_button = soup.select_one('input[type="submit"][id^="form_rcdl:j_idt"]')
if not submit_button:
    print("Error: Couldn't find the submit button ID")
    sys.exit(1)
button_id = submit_button['id']

# Update your data dictionary with the dynamic ID
data = {
    'javax.faces.partial.ajax':'true',
    'javax.faces.source': button_id,
    'javax.faces.partial.execute':'@all',
    'javax.faces.partial.render': 'form_rcdl:pnl_show form_rcdl:pg_show form_rcdl:rcdl_pnl',
    button_id: button_id,
    'form_rcdl':'form_rcdl',
    'form_rcdl:tf_reg_no1': first,
    'form_rcdl:tf_reg_no2': second,
    'javax.faces.ViewState': viewstate,
}

3. Add Argument Validation (Avoid Silent Crashes) #

Since you’re using command-line arguments, a missing input will crash the script silently if you don’t add checks. Let’s add a quick validation at the start:

if len(sys.argv) != 3:
    print("Usage: python your_script.py <first_part> <last_four_digits>")
    print("Example: python your_script.py GJ03KA 0803")
    sys.exit(1)

first = sys.argv[1]
second = sys.argv[2]

4. Debugging Steps to See What’s Happening #

Add print statements to verify if your requests are succeeding and what content you’re getting back:

# After the initial GET request
print(f"GET Request Status: {r.status_code}")
if r.status_code != 200:
    print("Error: Failed to load the homepage")
    sys.exit(1)

# After the POST request
print(f"POST Request Status: {r.status_code}")
print(f"POST Response Preview: {r.text[:500]}")  # Print first 500 characters of the response

• A 403 status code means you’re being blocked (the User-Agent fix should resolve this).
• A 200 status with empty or JS-heavy content might mean you need to use a tool like Selenium to handle dynamic rendering, but let’s try the simpler fixes first.

5. Verify ViewState Extraction #

Make sure you’re correctly grabbing the ViewState (it might be missing or in a different element):

viewstate_elements = soup.select('input[name="javax.faces.ViewState"]')
if not viewstate_elements:
    print("Error: Couldn't find ViewState")
    sys.exit(1)
viewstate = viewstate_elements[0]['value']

Try implementing these fixes one by one—start with the User-Agent header, as that’s the most common issue with government site scraping.

内容的提问来源于stack exchange，提问作者Shubham Sejpal