how to loop through files in a directory python

import os
directory = 'the/directory/you/want/to/use'

for filename in os.listdir(directory):
    if filename.endswith(".txt"):
      #do smth
      continue
    else:
    continue

import os

for filename in os.listdir(directory):
	print(filename)

import os

for filename in os.listdir(directory):
    if filename.endswith(".asm") or filename.endswith(".py"): 
         # print(os.path.join(directory, filename))
        continue
    else:
        continue

import os

for filename in os.listdir(directory):
    if filename.endswith(".asm") or filename.endswith(".py"): 
         # print(os.path.join(directory, filename))
        continue
    else:
        continue

basepath = "pathtodir/DataFiles/"
for filename in os.listdir(basepath):
    if filename.endswith(".log"): 
        print(os.path.join("./DataFiles", filename))

        with open(basepath + filename) as openfile:    
            for line in openfile:
            ........