filename='ext.tar.gz'
extension = filename[filename.rfind('.'):]

如果您想提取最后一个文件扩展名，如果它有多个

class functions:
    def listdir(self, filepath):
        return os.listdir(filepath)
    
func = functions()

os.chdir("C:\\Users\Asus-pc\Downloads") #absolute path, change this to your directory
current_dir = os.getcwd()

for i in range(len(func.listdir(current_dir))): #i is set to numbers of files and directories on path directory
    if os.path.isfile((func.listdir(current_dir))[i]): #check if it is a file
        fileName = func.listdir(current_dir)[i] #put the current filename into a variable
        rev_fileName = fileName[::-1] #reverse the filename
        currentFileExtension = rev_fileName[:rev_fileName.index('.')][::-1] #extract from beginning until before .
        print(currentFileExtension) #output can be mp3,pdf,ini,exe, depends on the file on your absolute directory

输出为mp3，即使只有一个扩展名也能正常工作

另一种右拆分解决方案：

# to get extension only

s = 'test.ext'

if '.' in s: ext = s.rsplit('.', 1)[1]

# or, to get file name and extension

def split_filepath(s):
    """
    get filename and extension from filepath 
    filepath -> (filename, extension)
    """
    if not '.' in s: return (s, '')
    r = s.rsplit('.', 1)
    return (r[0], r[1])

使用os.path.splitext：

>>> import os
>>> filename, file_extension = os.path.splitext('/path/to/somefile.ext')
>>> filename
'/path/to/somefile'
>>> file_extension
'.ext'

与大多数手动字符串拆分尝试不同，os.path.splitext将正确地将/a/b.c/d视为没有扩展名而不是扩展名.c/d，并将.bashrc视为没有延伸名而不是具有扩展名.bashrc：

>>> os.path.splitext('/a/b.c/d')
('/a/b.c/d', '')
>>> os.path.splitext('.bashrc')
('.bashrc', '')

此方法需要字典、列表或集合。您可以使用内置字符串方法使用“.endswitch”。这将在文件末尾的列表中搜索名称，只需使用str.endswith（fileName[index]）即可完成。这更多用于获取和比较扩展名。

https://docs.python.org/3/library/stdtypes.html#string-方法

示例1：

dictonary = {0:".tar.gz", 1:".txt", 2:".exe", 3:".js", 4:".java", 5:".python", 6:".ruby",7:".c", 8:".bash", 9:".ps1", 10:".html", 11:".html5", 12:".css", 13:".json", 14:".abc"} 
for x in dictonary.values():
    str = "file" + x
    str.endswith(x, str.index("."), len(str))

示例2：

set1 = {".tar.gz", ".txt", ".exe", ".js", ".java", ".python", ".ruby", ".c", ".bash", ".ps1", ".html", ".html5", ".css", ".json", ".abc"}
for x in set1:
   str = "file" + x
   str.endswith(x, str.index("."), len(str))

示例3：

fileName = [".tar.gz", ".txt", ".exe", ".js", ".java", ".python", ".ruby", ".c", ".bash", ".ps1", ".html", ".html5", ".css", ".json", ".abc"];
for x in range(0, len(fileName)):
    str = "file" + fileName[x]
    str.endswith(fileName[x], str.index("."), len(str))

示例4

fileName = [".tar.gz", ".txt", ".exe", ".js", ".java", ".python", ".ruby", ".c", ".bash", ".ps1", ".html", ".html5", ".css", ".json", ".abc"];
str = "file.txt"
str.endswith(fileName[1], str.index("."), len(str))

具有输出的示例5、6、7

示例8

fileName = [".tar.gz", ".txt", ".exe", ".js", ".java", ".python", ".ruby", ".c", ".bash", ".ps1", ".html", ".html5", ".css", ".json", ".abc"];
exts = []
str = "file.txt"
for x in range(0, len(x)):
    if str.endswith(fileName[1]) == 1:
         exts += [x]
     

def NewFileName(fichier):
    cpt = 0
    fic , *ext =  fichier.split('.')
    ext = '.'.join(ext)
    while os.path.isfile(fichier):
        cpt += 1
        fichier = '{0}-({1}).{2}'.format(fic, cpt, ext)
    return fichier