How can I iterate over files in a given directory?

You can try using glob module:

import glob

for filepath in glob.iglob('my_dir/*.asm'):
    print(filepath)

and since Python 3.5 you can search subdirectories as well:

glob.glob('**/*.txt', recursive=True) # => ['2.txt', 'sub/3.txt']

From the docs:

The glob module finds all the pathnames matching a specified pattern according to the rules used by the Unix shell, although results are returned in arbitrary order. No tilde expansion is done, but *, ?, and character ranges expressed with [] will be correctly matched.

This will iterate over all descendant files, not just the immediate children of the directory:

import os

for subdir, dirs, files in os.walk(rootdir):
    for file in files:
        #print os.path.join(subdir, file)
        filepath = subdir + os.sep + file

        if filepath.endswith(".asm"):
            print (filepath)

Python 3.4 and later offer pathlib in the standard library. You could do:

from pathlib import Path

asm_pths = [pth for pth in Path.cwd().iterdir()
            if pth.suffix == '.asm']

Or if you don’t like list comprehensions:

asm_paths = []
for pth in Path.cwd().iterdir():
    if pth.suffix == '.asm':
        asm_pths.append(pth)

Path objects can easily be converted to strings.

I’m not quite happy with this implementation yet, I wanted to have a custom constructor that does DirectoryIndex._make(next(os.walk(input_path))) such that you can just pass the path you want a file listing for. Edits welcome!

import collections
import os

DirectoryIndex = collections.namedtuple('DirectoryIndex', ['root', 'dirs', 'files'])

for file_name in DirectoryIndex(*next(os.walk('.'))).files:
    file_path = os.path.join(path, file_name)

Here’s how I iterate through files in Python:

import os

path = 'the/name/of/your/path'

folder = os.fsencode(path)

filenames = []

for file in os.listdir(folder):
    filename = os.fsdecode(file)
    if filename.endswith( ('.jpeg', '.png', '.gif') ): # whatever file types you're using...
        filenames.append(filename)

filenames.sort() # now you have the filenames and can do something with them

NONE OF THESE TECHNIQUES GUARANTEE ANY ITERATION ORDERING

Yup, super unpredictable. Notice that I sort the filenames, which is important if the order of the files matters, i.e. for video frames or time dependent data collection. Be sure to put indices in your filenames though!

Since Python 3.5, things are much easier with os.scandir() and 2-20x faster (source):

with os.scandir(path) as it:
    for entry in it:
        if entry.name.endswith(".asm") and entry.is_file():
            print(entry.name, entry.path)

Using scandir() instead of listdir() can significantly increase the
performance of code that also needs file type or file attribute
information, because os.DirEntry objects expose this information if
the operating system provides it when scanning a directory. All
os.DirEntry methods may perform a system call, but is_dir() and
is_file() usually only require a system call for symbolic links;
os.DirEntry.stat() always requires a system call on Unix but only
requires one for symbolic links on Windows.

I really like using the scandir directive that is built into the os library. Here is a working example:

import os

i = 0
with os.scandir('/usr/local/bin') as root_dir:
    for path in root_dir:
        if path.is_file():
            i += 1
            print(f"Full path is: {path} and just the name is: {path.name}")
print(f"{i} files scanned successfully.")

You can use glob for referring the directory and the list :

import glob
import os

#to get the current working directory name
cwd = os.getcwd()
#Load the images from images folder.
for f in glob.glob('images*.jpg'):   
    dir_name = get_dir_name(f)
    image_file_name = dir_name + '.jpg'
    #To print the file name with path (path will be in string)
    print (image_file_name)

To get the list of all directory in array you can use os :

os.listdir(directory)

Get all the .asm files in a directory by doing this.

import os

path = "path_to_file"
file_type = '.asm'

for filename in os.listdir(path=path):
    if filename.endswith(file_type):
        print(filename)
        print(f"{path}/{filename}")
        # do something below
  

I don’t understand why some answers are complicated. This is how I would do it with Python 2.7. Replace DIRECTORY_TO_LOOP with the directory you want to use.

import os
DIRECTORY_TO_LOOP = '/var/www/files/'
for root, dirs, files in os.walk(DIRECTORY_TO_LOOP, topdown=False):
   for name in files:
      print(os.path.join(root, name))