http://moscow.sci-hub.io/abc123blah/foo.pdf 的 pdf url。如果您随后请求该链接，您将随机获得 pdf 或验证码。 验证码页面有这个来源：
<html>
<head>
<title>Для просмотра статьи разгадайте капчу</title>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
</head>
<body style = "background:white">
<div>
<table style = "width:100%;height:100%"><tr><td style = "vertical-align:middle;text-align:center">
<h2 style = "color:gray;font-family:sans-serif;padding:18px">для просмотра статьи разгадайте капчу</h2>
<p></p>
<form action = "" method = "POST">
<p><img id="captcha" src="/captcha/securimage_show.php" /></p>
<input type="text" maxlength="6" name="captcha_code" style = "width:256px;font-size:18px;height:36px;margin-top:18px;text-align:center" autofocus /><br>
<a style = "color:gray;text-decoration:none" href="#" onclick="document.getElementById('captcha').src = '/captcha/securimage_show.php?' + Math.random(); return false">[ показать другую картинку ]</a>
<p style = "margin-top:22px"><input type = "submit" value= "Продолжить"></p>
</form>
</td></tr></table>
</div>
</body>
</html>
我能想到的就是请求 secureimage_show.php，保存图像，将其显示给用户，获取其解码，然后发布响应。示例 pdf 链接是
http://moscow.sci-hub.io/291193c259b69cc057d74e3eb4965c4f/ong2014.pdf 比如：
import requests
from PIL import Image
import io
pdf_url = "http://moscow.sci-hub.io/3dcd1bf3b82ea549c0a72e9ab195ab78/walter2015.pdf"
r1 = requests.get(pdf_url)
if r1.headers['Content-Type'] != 'application/pdf':
print("Looks like Sci-hub gave us a captcha")
image = requests.get("http://moscow.sci-hub.io/captcha/securimage_show.php").content
img = io.BytesIO(image)
im = Image.open(img)
im.show()
captcha_text = input("Enter captcha text: ")
r2 = requests.post(pdf_url, data = {'captcha_code': captcha_text})
if r2.headers['Content-Type'] != 'application/pdf':
print("Looks like Sci-hub gave us another captcha")
else:
with open("filename.pdf", 'wb') as f:
f.write(r.content)
print("saved!")
else:
print("Got a PDF")
with open("filename.pdf", 'wb') as f:
f.write(r.content)
print("saved!")
我没有办法获取我第一次请求 pdf 时生成的原始验证码图像。当我从 secureimage_show.php 请求另一个验证码图像时，它会生成一个新图像，因此 POST 响应不正确。我该如何解决这个问题？
import requests
from PIL import Image
from io import BytesIO
pdf_url = "http://moscow.sci-hub.io/3dcd1bf3b82ea549c0a72e9ab195ab78/walter2015.pdf"
s = requests.Session()
r1 = s.get(pdf_url)
if r1.headers['Content-Type'] != 'application/pdf':
print("Looks like Sci-hub gave us a captcha")
image = s.get("http://moscow.sci-hub.io/captcha/securimage_show.php").content
img = BytesIO(image)
im = Image.open(img)
im.show()
captcha_text = input("Enter captcha text: ")
r2 = s.post(pdf_url, data = {'captcha_code': captcha_text})
if r2.headers['Content-Type'] != 'application/pdf':
print("Looks like Sci-hub gave us another captcha")
else:
with open("filename.pdf", 'wb') as f:
f.write(r2.content)
print("saved!")
else:
print("Got a PDF")
with open("filename.pdf", 'wb') as f:
f.write(r1.content)
print("saved!")