如何用Python的Selenium从Blob URL下载CSV文件？

问题背景 #

我想用Python的Selenium自动化下载动态网站中Blob URL对应的CSV文件，CSV下载由点击按钮触发，但点击后生成的Blob URL无法通过传统HTTP请求直接访问，难以捕获并下载对应文件。

• 示例页面：https://snapshot.org/#/aave.eth/proposal/0x70dfd865b78c4c391e2b0729b907d152e6e8a0da683416d617d8f84782036349
• Blob URL示例：blob:https://snapshot.org/4b2f45e9-8ca3-4105-b142-e1877e420c84

手动点击按钮能成功获取文件，但现有自动化代码无法完成下载，尝试过的代码如下：

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.chrome.service import Service
from webdriver_manager.chrome import ChromeDriverManager
import time

# Setup ChromeDriver
driver = webdriver.Chrome(service=Service(ChromeDriverManager().install()))

# URL of the proposal page
url = 'https://snapshot.org/#/aave.eth/proposal/0x70dfd865b78c4c391e2b0729b907d152e6e8a0da683416d617d8f84782036349'

# Navigate to the page
driver.get(url)

try:
    # Wait up to 20 seconds until the expected button is found using its attributes
    wait = WebDriverWait(driver, 20)
    download_button = wait.until(EC.element_to_be_clickable((By.XPATH, "//button[contains(.,'svg')]")))
    download_button.click()
    print("Download initiated.")
except Exception as e:
    print(f"Error: {e}")

# Wait for the download to complete
time.sleep(5)

# Close the browser
driver.quit()

下载按钮对应的元素代码：

<svg viewBox="0 0 24 24" width="1.2em" height="1.2em"><path fill="none" stroke="currentColor" stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M4 16v1a3 3 0 0 0 3 3h10a3 3 0 0 0 3-3v-1m-4-4l-4 4m0 0l-4-4m4 4V4"></path></svg>

解决方案 #

方法一：拦截Blob构造函数，直接提取文件内容 #

Blob是前端在浏览器内部生成的，我们可以通过注入JavaScript脚本拦截Blob的创建过程，提取CSV内容后保存到本地。

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.chrome.service import Service
from webdriver_manager.chrome import ChromeDriverManager
import time

# 注入拦截Blob的脚本，捕获CSV内容
intercept_blob_script = """
window.originalBlob = Blob;
window.blobData = null;
Blob = function(parts, options) {
    const blob = new window.originalBlob(parts, options);
    // 只拦截CSV类型的Blob
    if (options?.type === 'text/csv') {
        const reader = new FileReader();
        reader.onload = function() {
            window.blobData = reader.result;
        };
        reader.readAsText(blob);
    }
    return blob;
};
"""

# 配置Chrome选项
options = webdriver.ChromeOptions()
options.add_experimental_option("prefs", {
    "download.prompt_for_download": False,
    "download.directory_upgrade": True
})

# 初始化驱动并注入脚本
driver = webdriver.Chrome(service=Service(ChromeDriverManager().install()), options=options)
driver.execute_script(intercept_blob_script)

# 访问目标页面
url = 'https://snapshot.org/#/aave.eth/proposal/0x70dfd865b78c4c391e2b0729b907d152e6e8a0da683416d617d8f84782036349'
driver.get(url)

try:
    # 精准定位下载按钮：通过SVG路径的d属性匹配
    wait = WebDriverWait(driver, 20)
    download_button = wait.until(EC.element_to_be_clickable((By.XPATH, "//button[.//path[@d='M4 16v1a3 3 0 0 0 3 3h10a3 3 0 0 0 3-3v-1m-4-4l-4 4m0 0l-4-4m4 4V4']]")))
    download_button.click()
    print("下载已触发")
    
    # 等待数据捕获完成
    time.sleep(3)
    blob_data = driver.execute_script("return window.blobData;")
    
    if blob_data:
        # 保存CSV文件
        with open('proposal_votes.csv', 'w', encoding='utf-8') as f:
            f.write(blob_data)
        print("CSV文件已成功保存")
    else:
        print("未捕获到Blob数据")
        
except Exception as e:
    print(f"错误：{e}")

driver.quit()

方法二：配置Chrome自动下载，直接获取本地文件 #

通过设置Chrome的下载偏好，让文件自动保存到指定目录，再读取下载完成的文件。

from selenium import webdriver
from selenium.webdriver.common.by import By
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from selenium.webdriver.chrome.service import Service
from webdriver_manager.chrome import ChromeDriverManager
import os
import time
from glob import glob

# 设置下载目录
download_dir = os.path.abspath('./downloads')
os.makedirs(download_dir, exist_ok=True)

# 配置Chrome下载偏好
options = webdriver.ChromeOptions()
prefs = {
    "download.default_directory": download_dir,
    "download.prompt_for_download": False,
    "download.directory_upgrade": True,
    "safebrowsing.enabled": True
}
options.add_experimental_option("prefs", prefs)

# 初始化驱动
driver = webdriver.Chrome(service=Service(ChromeDriverManager().install()), options=options)

# 访问目标页面
url = 'https://snapshot.org/#/aave.eth/proposal/0x70dfd865b78c4c391e2b0729b907d152e6e8a0da683416d617d8f84782036349'
driver.get(url)

try:
    # 精准定位下载按钮
    wait = WebDriverWait(driver, 20)
    download_button = wait.until(EC.element_to_be_clickable((By.XPATH, "//button[.//path[@d='M4 16v1a3 3 0 0 0 3 3h10a3 3 0 0 0 3-3v-1m-4-4l-4 4m0 0l-4-4m4 4V4']]")))
    download_button.click()
    print("下载已触发")
    
    # 等待下载完成
    time.sleep(5)
    
    # 查找最新下载的CSV文件
    csv_files = glob(os.path.join(download_dir, '*.csv'))
    if csv_files:
        latest_file = max(csv_files, key=os.path.getctime)
        print(f"CSV文件已下载到：{latest_file}")
    else:
        print("未找到下载的CSV文件")
        
except Exception as e:
    print(f"错误：{e}")

driver.quit()

关键说明 #

1. 按钮定位问题：原代码使用//button[contains(.,'svg')]会匹配多个带SVG的按钮，改用SVG路径的d属性可以精准定位下载按钮。
2. Blob URL无法直接访问的原因：Blob URL是浏览器内部生成的临时URL，仅在当前会话有效，无法通过外部HTTP请求访问，必须从浏览器内部提取数据。

内容的提问来源于stack exchange，提问作者rischan