How to safely get the file extension from a URL?

Consider the following URLs

http://m3u.com/tunein.m3u
http://asxsomeurl.com/li开发者_如何学编程sten.asx:8024
http://www.plssomeotherurl.com/station.pls?id=111
http://22.198.133.16:8024

Whats the proper way to determine the file extensions (.m3u/.asx/.pls)? Obviously the last one doesn't have a file extension.

EDIT: I forgot to mention that m3u/asx/pls are playlists (textfiles) for audio streams and must be parsed differently. The goal determine the extension and then send the url to the proper parsing-function. E.g.

url = argv[1]
ext = GetExtension(url)
if ext == "pls":
  realurl = ParsePLS(url)
elif ext == "asx":
  realurl = ParseASX(url)
(etc.)
else:
  realurl = url
Play(realurl)

GetExtension() should return the file extension (if any), preferrably without connecting to the URL.

---

Use urlparse to parse the path out of the URL, then os.path.splitext to get the extension.

import os
try:
    import urlparse
except ImportError:
    from urllib.parse import urlparse

url = 'http://www.plssomeotherurl.com/station.pls?id=111'
path = urlparse.urlparse(url).path
ext = os.path.splitext(path)[1]

Note that the extension may not be a reliable indicator of the type of the file. The HTTP Content-Type header may be better.

---

This is easiest with requests and mimetypes:

import requests
import mimetypes

response = requests.get(url)
content_type = response.headers['content-type']
extension = mimetypes.guess_extension(content_type)

The extension includes a dot prefix. For example, extension is '.png' for content type 'image/png'.

---

The real proper way is to not use file extensions at all. Do a GET (or HEAD) request to the URL in question, and use the returned "Content-type" HTTP header to get the content type. File extensions are unreliable.

See MIME types (IANA media types) for more information and a list of useful MIME types.

---

File extensions are basically meaningless in URLs. For example, if you go to http://code.google.com/p/unladen-swallow/source/browse/branches/release-2009Q1-maint/Lib/psyco/support.py?r=292 do you want the extension to be ".py" despite the fact that the page is HTML, not Python?

Use the Content-Type header to determine the "type" of a URL.

---

$ python3
Python 3.1.2 (release31-maint, Sep 17 2010, 20:27:33) 
[GCC 4.4.5] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> from os.path import splitext
>>> from urllib.parse import urlparse 
>>> 
>>> urls = [
...     'http://m3u.com/tunein.m3u',
...     'http://asxsomeurl.com/listen.asx:8024',
...     'http://www.plssomeotherurl.com/station.pls?id=111',
...     'http://22.198.133.16:8024',
... ]
>>> 
>>> for url in urls:
...     path = urlparse(url).path
...     ext = splitext(path)[1]
...     print(ext)
... 
.m3u
.asx:8024
.pls

>>> 

---

To get the content-type you can write a function one like I have written using urllib2. If you need to utilize page content anyway it is likely that you will use urllib2 so no need to import os.

import urllib2

def getContentType(pageUrl):
    page = urllib2.urlopen(pageUrl)
    pageHeaders = page.headers
    contentType = pageHeaders.getheader('content-type')
    return contentType

---

Use urlparse, that'll get most of the above sorted:

http://docs.python.org/library/urlparse.html

then split the "path" up. You might be able to split the path up using os.path.split, but your example 2 with the :8024 on the end needs manual handling. Are your file extensions always three letters? Or always letters and numbers? Use a regular expression.

---

A different approach that takes nothing else into account except for the actual file extension from a url:

def fileExt( url ):
    # compile regular expressions
    reQuery = re.compile( r'\?.*$', re.IGNORECASE )
    rePort = re.compile( r':[0-9]+', re.IGNORECASE )
    reExt = re.compile( r'(\.[A-Za-z0-9]+$)', re.IGNORECASE )

    # remove query string
    url = reQuery.sub( "", url )

    # remove port
    url = rePort.sub( "", url )

    # extract extension
    matches = reExt.search( url )
    if None != matches:
        return matches.group( 1 )
    return None

edit: added handling of explicit ports from :1234

---

you can try the rfc6266 module like：

import requests
import rfc6266

req = requests.head(downloadLink)
headersContent = req.headers['Content-Disposition']
rfcFilename = rfc6266.parse_headers(headersContent, relaxed=True).filename_unsafe
filename = requests.utils.unquote(rfcFilename)

---

This is quite an old topic, but this oneliner is what did:

file_ext = "."+ url.split("/")[-1:][0].split(".")[-1:][0]

Assumption is that there is a file extension.