How to list all files in a folder using Python?

There are different ways to get all files from a directory. Below are different ways, all of them return a list by calling them like this:

lista_arq = ls(ruta)   # no especificar ruta para tomar el directorio actual

1. Higher efficiency with os.scandir() - python-3.5

   Returns a iterator to objects that maintain file properties, making it more efficient (for example, you don't need to make a system call to see if an object is a file or a directory).

   from os import scandir, getcwd
   
   def ls(ruta = getcwd()):
       return [arch.name for arch in scandir(ruta) if arch.is_file()]
   

   Or if you want to get the absolute path of each file:

   from os import scandir, getcwd
   from os.path import abspath
   
   def ls(ruta = getcwd()):
       return [abspath(arch.path) for arch in scandir(ruta) if arch.is_file()]
   

1. With the Library pathlib and its main classPath - python-3.4

   Provides higher level of consistency between different operating systems, without the need to reference directly to os, avoiding also many calls to the system.

   from pathlib import Path
   
   def ls(ruta = Path.cwd()):
       return [arch.name for arch in Path(ruta).iterdir() if arch.is_file()]
   

   ^{* thanks to kikocorreoso for the reference and your article of joyitas.}

1. List all directories and files with listdir() - python-2.x y python-3.x

   from os import listdir
   
   def ls(ruta = '.'):
       return listdir(ruta)
   

   Or just files :

   from os import listdir
   from os.path import isfile, join
   
   def ls(ruta = '.'):
       return [arch for arch in listdir(ruta) if isfile(join(ruta, arch))]
   

1. Greater control with os.walk() - python-2.2 and python-3.x

   You can get only files more compactly :

   from os import walk
   
   def ls(ruta = '.'):
       return next(walk(ruta))[2]
   

   Or you can have more control if you want, getting two lists ( directories and files )

   from os import walk
   
   def ls(ruta = '.'):
       dir, subdirs, archivos = next(walk(ruta))
       print("Actual: ", dir)
       print("Subdirectorios: ", subdirs)
       print("Archivos: ", archivos)
       return archivos
   

   And if you also want to get files from all subdirectories, you can iterate as follows:

   from os import walk, getcwd
   
   def ls(ruta = getcwd()):
       listaarchivos = []
       for (_, _, archivos) in walk(ruta):
           listaarchivos.extend(archivos)
       return listaarchivos
   

1. Using wildcards in glob() - python-2.x y python-3.x

   To search for files using wildcards (*, ?, [seq] and [!seq])

   from glob import glob
   
   def ls(expr = '*.*'):
       return glob(expr)
   

   This function returns the full path of each file.

   Example:

   print(ls('/etc/*.conf'))
   

1. Find files with a regular expression - python-2.2 y python-3.x

   from os import walk, getcwd, path
   import re
   
   def ls(regex = '', ruta = getcwd()):
       pat = re.compile(regex, re.I)
       resultado = []
       for (dir, _, archivos) in walk(ruta):
           resultado.extend([ path.join(dir,arch) for arch in 
                                 filter(pat.search, archivos) ])
           # break  # habilitar si no se busca en subdirectorios
       return resultado
   

   Example:

   print(ls( r'-\d+\.[^.\d]*$', '/'))