python遍历文件夹图片

def getFileList('/home/aistudio/work/chpa/img',Filelist ,'jpg'=None):

newDir ='/home/aistudio/work/chpa/img'
if os.path.isfile(newDir):
    if 'jpg' is None:
        Filelist.append(newDir)
    else:
        if 'jpg' in newDir[-3:]:
            Filelist.append(newDir)

elif os.path.isdir(newDir):
    for s in os.listdir(newDir):
        newDir = os.path.join(newDir, s)
        getFileList(newDir, Filelist, 'jpg')

return Filelist

def getFileList('/home/aistudio/work/chpa/img',Filelist ,'jpg'=None) 报错
想要实现一个文件中100张图片的遍历


import os

def getFileList(directory, filelist, extension='jpg'):
    if os.path.isfile(directory):
        if extension is None:
            filelist.append(directory)
        else:
            if extension in directory[-len(extension):]:
                filelist.append(directory)
    elif os.path.isdir(directory):
        for filename in os.listdir(directory):
            filepath = os.path.join(directory, filename)
            getFileList(filepath, filelist, extension)
    return filelist

# Example usage
directory = '/home/aistudio/aistudiowork/chpa/img'
filelist = []
extension = 'jpg'
filelist = getFileList(directory, filelist, extension)
print(filelist)

'jpg'=None是啥，你给字符串赋值？？