Python requests 下载文件的几种常用方法

1. 基础下载：

import requests

def download_file(url, save_path):
    response = requests.get(url, stream=True)
    if response.status_code == 200:
        with open(save_path, 'wb') as f:
            f.write(response.content)
        return True
    return False

# 使用示例
url = "https://example.com/file.pdf"
download_file(url, "file.pdf")

2. 大文件分块下载：

import requests
from tqdm import tqdm

def download_large_file(url, save_path):
    response = requests.get(url, stream=True)
    if response.status_code == 200:
        file_size = int(response.headers.get('content-length', 0))
        
        # 显示进度条
        progress = tqdm(response.iter_content(chunk_size=8192), 
                       total=file_size,
                       unit='B', 
                       unit_scale=True)
        
        with open(save_path, 'wb') as f:
            for data in progress:
                f.write(data)
        return True
    return False

3. 带有断点续传的下载：

import requests
import os

def resume_download(url, save_path):
    # 获取已下载文件大小
    initial_pos = os.path.getsize(save_path) if os.path.exists(save_path) else 0
    
    # 设置 Header
    headers = {'Range': f'bytes={initial_pos}-'}
    
    response = requests.get(url, stream=True, headers=headers)
    
    # 追加模式打开文件
    mode = 'ab' if initial_pos > 0 else 'wb'
    with open(save_path, mode) as f:
        for chunk in response.iter_content(chunk_size=8192):
            if chunk:
                f.write(chunk)

4. 带有超时和重试的下载：

import requests
from requests.adapters import HTTPAdapter
from requests.packages.urllib3.util.retry import Retry
import time

def download_with_retry(url, save_path, max_retries=3, timeout=30):
    session = requests.Session()
    
    # 设置重试策略
    retries = Retry(total=max_retries,
                   backoff_factor=1,
                   status_forcelist=[500, 502, 503, 504])
    
    session.mount('http://', HTTPAdapter(max_retries=retries))
    session.mount('https://', HTTPAdapter(max_retries=retries))
    
    try:
        response = session.get(url, stream=True, timeout=timeout)
        with open(save_path, 'wb') as f:
            for chunk in response.iter_content(chunk_size=8192):
                if chunk:
                    f.write(chunk)
        return True
    except Exception as e:
        print(f"Download failed: {str(e)}")
        return False

5. 完整的下载器实现：

import requests
from tqdm import tqdm
import os
from pathlib import Path
import hashlib

class FileDownloader:
    def __init__(self, chunk_size=8192):
        self.chunk_size = chunk_size
        self.session = requests.Session()
        
    def get_file_size(self, url):
        response = self.session.head(url)
        return int(response.headers.get('content-length', 0))
    
    def get_file_hash(self, file_path):
        sha256_hash = hashlib.sha256()
        with open(file_path, "rb") as f:
            for byte_block in iter(lambda: f.read(4096), b""):
                sha256_hash.update(byte_block)
        return sha256_hash.hexdigest()
    
    def download(self, url, save_path, verify_hash=None):
        save_path = Path(save_path)
        
        # 创建目录
        save_path.parent.mkdir(parents=True, exist_ok=True)
        
        # 获取文件大小
        file_size = self.get_file_size(url)
        
        # 设置进度条
        progress = tqdm(total=file_size,
                       unit='B',
                       unit_scale=True,
                       desc=save_path.name)
        
        try:
            response = self.session.get(url, stream=True)
            with save_path.open('wb') as f:
                for chunk in response.iter_content(chunk_size=self.chunk_size):
                    if chunk:
                        f.write(chunk)
                        progress.update(len(chunk))
            
            progress.close()
            
            # 验证文件完整性
            if verify_hash:
                downloaded_hash = self.get_file_hash(save_path)
                if downloaded_hash != verify_hash:
                    raise ValueError("File hash verification failed")
                    
            return True
            
        except Exception as e:
            progress.close()
            print(f"Download failed: {str(e)}")
            if save_path.exists():
                save_path.unlink()
            return False
            
    def download_multiple(self, url_list, save_dir):
        results = []
        for url in url_list:
            filename = url.split('/')[-1]
            save_path = Path(save_dir) / filename
            success = self.download(url, save_path)
            results.append({
                'url': url,
                'success': success,
                'save_path': str(save_path)
            })
        return results

# 使用示例
downloader = FileDownloader()

# 单文件下载
url = "https://example.com/file.pdf"
downloader.download(url, "downloads/file.pdf")

# 多文件下载
urls = [
    "https://example.com/file1.pdf",
    "https://example.com/file2.pdf"
]
results = downloader.download_multiple(urls, "downloads")

作者：microhex