在Python 3中从Web下载文件

Download file from web in Python 3

我正在创建一个程序，它将通过读取在同一游戏/应用程序的.jad文件中指定的URL来从Web服务器下载.jar(Java)文件。我使用的是python 3.2.1

我已经设法从jad文件中提取jar文件的URL(每个jad文件都包含jar文件的URL)，但是正如您所想象的，提取的值是type()字符串。

如果要将网页内容转换为变量，只需readurllib.request.urlopen的响应即可：

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import urllib.request
...
url = 'http://example.com/'
response = urllib.request.urlopen(url)
data = response.read() # a `bytes` object
text = data.decode('utf-8') # a `str`; this step can't be used if data is binary

下载和保存文件的最简单方法是使用urllib.request.urlretrieve功能：

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import urllib.request
...
# Download the file from `url` and save it locally under `file_name`:
urllib.request.urlretrieve(url, file_name)

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import urllib.request
...
# Download the file from `url`, save it in a temporary directory and get the
# path to it (e.g. '/tmp/tmpb48zma.txt') in the `file_name` variable:
file_name, headers = urllib.request.urlretrieve(url)

但请记住，urlretrieve被视为遗产，可能会被弃用(但不确定为什么)。

因此，最正确的方法是使用urllib.request.urlopen函数返回表示HTTP响应的类似文件的对象，并使用shutil.copyfileobj将其复制到实际文件中。

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import urllib.request
import shutil
...
# Download the file from `url` and save it locally under `file_name`:
with urllib.request.urlopen(url) as response, open(file_name, 'wb') as out_file:
shutil.copyfileobj(response, out_file)

如果这看起来太复杂，您可能需要更简单地将整个下载内容存储在一个bytes对象中，然后将其写入一个文件。但这只适用于小文件。

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import urllib.request
...
# Download the file from `url` and save it locally under `file_name`:
with urllib.request.urlopen(url) as response, open(file_name, 'wb') as out_file:
data = response.read() # a `bytes` object
out_file.write(data)

可以实时提取.gz压缩数据(或者其他格式)，但这种操作可能需要HTTP服务器支持对文件的随机访问。

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import urllib.request
import gzip
...
# Read the first 64 bytes of the file inside the .gz archive located at `url`
url = 'http://example.com/something.gz'
with urllib.request.urlopen(url) as response:
with gzip.GzipFile(fileobj=response) as uncompressed:
file_header = uncompressed.read(64) # a `bytes` object
# Or do anything shown above using `uncompressed` instead of `response`.

相关讨论

每当我需要与HTTP请求相关的东西时，我都会使用requests包，因为它的API很容易从以下内容开始：

首先，安装requests。

1	$ pip install requests

然后代码：

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from requests import get # to make GET request

def download(url, file_name):
# open in binary mode
with open(file_name,"wb") as file:
# get request
response = get(url)
# write to file
file.write(response.content)

相关讨论

我希望我理解正确的问题，即：当URL存储在字符串类型中时，如何从服务器下载文件？

我下载文件并使用以下代码在本地保存：

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import requests

url = 'https://www.python.org/static/img/python-logo.png'
fileName = 'D:\Python\dwnldPythonLogo.png'
req = requests.get(url)
file = open(fileName, 'wb')
for chunk in req.iter_content(100000):
file.write(chunk)
file.close()

相关讨论

这里我们可以在python3中使用urlib的遗留接口：

以下函数和类是从python 2模块urlib(而不是urlib2)移植的。在将来的某个时候，它们可能会被弃用。

示例(2行代码)：

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import urllib.request

url = 'https://www.python.org/static/img/python-logo.png'
urllib.request.urlretrieve(url,"logo.png")

您可以使用wget，这是流行的下载shell工具。https://pypi.python.org/pypi/wget这是最简单的方法，因为它不需要打开目标文件。下面是一个例子。

是的，明确地说，请求是用于与HTTP请求相关的东西的很好的包。但是我们需要注意输入数据的编码类型，下面是一个解释差异的示例

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from requests import get

# case when the response is byte array
url = 'some_image_url'

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

# case when the response is text
# Here unlikely if the reponse content is of type **iso-8859-1** we will have to override the response encoding
url = 'some_page_url'

response = get(url)
# override encoding by real educated guess as provided by chardet
r.encoding = r.apparent_encoding

with open('output', 'w', encoding='utf-8') as file:
file.write(response.content)

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from urllib import request

def get(url):
with request.urlopen(url) as r:
return r.read()

def download(url, file=None):
if not file:
file = url.split('/')[-1]
with open(file, 'wb') as f:
f.write(get(url))