Download Files from URL using Python

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Python Download File from URL

When it comes to file retrieval, Python offers a robust set of tools and packages that are useful in a variety of applications, from web scraping to automating scripts and analyzing retrieved data. Downloading files from a URL programmatically is a useful skill to learn for various programming and data projects and workflows.

In this tutorial, you’ll learn how to:

• Download files from the Web using the standard library as well as third-party libraries in Python
• Stream data to download large files in manageable chunks
• Implement parallel downloads using a pool of threads
• Perform asynchronous downloads to fetch multiple files in bulk

In this tutorial, we will focus on demonstrating the process of downloading files from a URL using various Python libraries and methods. We will also discuss different scenarios and considerations when choosing an approach.

Facilitating File Downloads With Python

While it’s possible to download files from URLs using traditional command-line tools, Python provides several libraries that facilitate file retrieval. Using Python to download files offers several advantages.

One advantage is flexibility, as Python has a rich ecosystem of libraries, including ones that offer efficient ways to handle different file formats, protocols, and authentication methods. You can choose the most suitable Python tools to accomplish the task at hand and fulfill your specific requirements, whether you’re downloading from a plain-text CSV file or a complex binary file.

Another reason is portability. You may encounter situations where you’re working on cross-platform applications. In such cases, using Python is a good choice because it’s a cross-platform programming language. This means that Python code can run consistently across different operating systems, such as Windows, Linux, and macOS.

Using Python also offers the possibility of automating your processes, saving you time and effort. Some examples include automating retries if a download fails, retrieving and saving multiple files from URLs, and processing and storing your data in designated locations.

These are just a few reasons why downloading files using Python is better than using traditional command-line tools. Depending on your project requirements, you can choose the approach and library that best suits your needs.

Downloading a File from a URL in Python

In this section, we will cover two common methods for downloading files from a URL in Python: using the urllib module from the standard library and using the requests library.

Using urllib from the Standard Library

The urllib module is part of Python’s standard library and provides functions for working with URLs. To download a file from a URL using urllib, you can use the following code:

import urllib.request

url = 'https://example.com/file.zip'
filename = 'file.zip'

urllib.request.urlretrieve(url, filename)

In the above code, urlretrieve() function takes the URL of the file to be downloaded and the filename to save the file as. It downloads the file and saves it to the specified location.

Using the Third-Party requests Library

The requests library is a popular third-party library for making HTTP requests in Python. It provides a more convenient and flexible way to download files from URLs. To download a file from a URL using requests, you can use the following code:

import requests

url = 'https://example.com/file.zip'
filename = 'file.zip'

response = requests.get(url)
with open(filename, 'wb') as file:
    file.write(response.content)

In the above code, we use the get() function from the requests library to send an HTTP GET request to the specified URL. We then open a file in binary write mode and write the content of the response to the file.

Saving Downloaded Content to a File

After downloading a file from a URL, you might want to save its content to a file on your local machine. Both the urllib module and the requests library provide methods to save the downloaded content to a file.

As shown in the previous code examples, you can use the open() function to open a file in write mode and then write the content to the file using the write() method.

import urllib.request

url = 'https://example.com/file.zip'
filename = 'file.zip'

urllib.request.urlretrieve(url, filename)

import requests

url = 'https://example.com/file.zip'
filename = 'file.zip'

response = requests.get(url)
with open(filename, 'wb') as file:
    file.write(response.content)

Downloading a Large File in a Streaming Fashion

When downloading large files, it’s often more efficient to download the file in manageable chunks rather than loading the entire file into memory. Both the urllib module and the requests library support streaming, which allows you to download files in a streaming fashion.

Streaming downloads can be achieved using the urllib module’s urlretrieve() function by passing a callback function that writes the downloaded chunks to a file.

import urllib.request

url = 'https://example.com/large_file.zip'
filename = 'large_file.zip'

def write_chunk(chunk):
    with open(filename, 'ab') as file:
        file.write(chunk)

urllib.request.urlretrieve(url, filename, write_chunk)

In the above code, we define a write_chunk() function that takes a chunk of data as an argument and writes it to the file in append binary mode. We pass this function as a callback to the urlretrieve() function, which will invoke the callback for each chunk downloaded.

Similarly, the requests library supports streaming downloads by setting the stream parameter to True when making the request. This allows us to iterate over the response’s content in chunks and write them to a file.

import requests

url = 'https://example.com/large_file.zip'
filename = 'large_file.zip'

response = requests.get(url, stream=True)
with open(filename, 'wb') as file:
    for chunk in response.iter_content(chunk_size=8192):
        if chunk:
            file.write(chunk)

In the above code, we set the stream parameter to True when making the request to enable streaming. We then iterate over the response’s content in chunks using the iter_content() method, specifying the chunk size. We write each chunk to the file.

Performing Parallel File Downloads

To increase the speed of file downloads, you can perform parallel downloads using multiple threads or asynchronous programming. In this section, we will cover two approaches: using a pool of threads with the requests library and using the asynchronous aiohttp library.

Using a Pool of Threads with the requests Library

Using a pool of threads can help speed up file downloads by downloading multiple files simultaneously. This is especially useful when downloading multiple files from different URLs.

The requests library provides a Session object that you can use to make multiple requests concurrently using a pool of threads. Here’s an example of how to use a thread pool to download multiple files:

import requests
from concurrent.futures import ThreadPoolExecutor

urls = ['https://example.com/file1.zip', 'https://example.com/file2.zip', 'https://example.com/file3.zip']
filenames = ['file1.zip', 'file2.zip', 'file3.zip']

def download_file(url, filename):
    response = requests.get(url)
    with open(filename, 'wb') as file:
        file.write(response.content)

with ThreadPoolExecutor() as executor:
    executor.map(download_file, urls, filenames)

In the above code, we define a download_file() function that takes a URL and a filename as arguments and downloads the file. We use the ThreadPoolExecutor class from the concurrent.futures module to create a thread pool. We then use the map() method of the executor to apply the download_file() function to each URL and filename pair.

Using the Asynchronous aiohttp Library

Asynchronous programming allows for concurrent execution without blocking other tasks. The aiohttp library is a popular choice for asynchronous programming in Python. It provides an async-based HTTP client with support for various features like streaming, proxies, cookies, and more.

To perform asynchronous file downloads using aiohttp, you need to use the asyncio library for managing coroutines and event loops. Here’s an example of how to use aiohttp for asynchronous file downloads:

import asyncio
import aiohttp

urls = ['https://example.com/file1.zip', 'https://example.com/file2.zip', 'https://example.com/file3.zip']
filenames = ['file1.zip', 'file2.zip', 'file3.zip']

async def download_file(url, filename):
    async with aiohttp.ClientSession() as session:
        async with session.get(url) as response:
            with open(filename, 'wb') as file:
                while True:
                    chunk = await response.content.read(8192)
                    if not chunk:
                        break
                    file.write(chunk)

async def main():
    tasks = []
    for url, filename in zip(urls, filenames):
        tasks.append(download_file(url, filename))
    await asyncio.gather(*tasks)

if __name__ == '__main__':
    loop = asyncio.get_event_loop()
    loop.run_until_complete(main())

In the above code, we define an async function download_file() that takes a URL and a filename as arguments and downloads the file. We use the aiohttp.ClientSession class to create an HTTP client session. We then use the get() method of the session to make an asynchronous GET request to the URL. We iterate over the response’s content in chunks and write them to the file.

We define another asynchronous function main() that creates a list of tasks for each URL and filename pair. We then use asyncio.gather() to run the tasks concurrently.

Deciding Which Option to Choose

When deciding which approach to choose for downloading files from a URL in Python, consider the following factors:

File Sizes to Download

If you’re dealing with small file sizes, using the urllib module or the requests library may be sufficient. However, if you’re downloading large files, it’s recommended to use streaming or perform parallel downloads to improve performance.

User-Friendliness

The requests library provides a more user-friendly and intuitive API compared to the urllib module. It’s easier to work with, especially when making multiple requests and handling various authentication methods.

Additional Features and Flexibility

If you need additional features like streaming, proxies, retries, or authentication methods, the requests library and the aiohttp library offer more flexibility and support for these features.

Conclusion

Python provides a variety of libraries and methods for downloading files from URLs. In this tutorial, we covered the basics of downloading files using the urllib module from the standard library and the requests library. We also explored more advanced techniques such as saving downloaded content to a file, streaming downloads, performing parallel downloads, and using asynchronous programming.

By understanding the different options and considerations, you can choose the most suitable approach for your file download requirements in Python.