import os

files = []
folders = []

for folder in os.listdir("./folders"):
    folders.append("./folders/"+folder+"/")
    print(folders)

for folder in folders:
    files = []
    for file in os.listdir(folder):
        files.append(file)
        files.sort()
        print(files)
    for i in range(4):
        os.rename(folder+files[i], folder+str(i+1)+".jpg")
    print(files)