> For the complete documentation index, see [llms.txt](https://baozoulin.gitbook.io/python/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://baozoulin.gitbook.io/python/geng-duo-qing-qiu-xia-zai-fang-shi/32-xia-zai-wen-jian.md).

# 3.2  下载文件

```python
import os
os.makedirs('./img/', exist_ok=True)

IMAGE_URL = "https://morvanzhou.github.io/static/img/description/learning_step_flowchart.png"
```

## 使用 urlretrieve

在 urllib 模块中, 提供了一个下载功能 urlretrieve.

输入下载地址 IMAGE\_URL 和要存放的位置. 图片就会被自动下载过去

```python
from urllib.request import urlretrieve
urlretrieve(IMAGE_URL, './img/image1.png')
```

## 使用 request

```python
import requests
r = requests.get(IMAGE_URL)
with open('./img/image2.png', 'wb') as f:
    f.write(r.content)
```

如果要下载的是大文件, 比如视频等. requests 能下一点, 保存一点，而不是要全部下载完才能保存去另外的地方，这就是一个 chunk 一个 chunk 的下载.

使用 r.iter\_content(chunk\_size) 来控制每个 chunk 的大小, 然后在文件中写入这个 chunk 大小的数据.

```python
r = requests.get(IMAGE_URL, stream=True)    # stream loading

with open('./img/image3.png', 'wb') as f:
    for chunk in r.iter_content(chunk_size=32):
        f.write(chunk)
```


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