Finding the latest file in a folder

I'm a bit new to Python and sort of learning on my own. I wrote a small function to help me find the latest file in a directory. Taking a step back, it reads a bit janky and I was curious what steps or what resources I could look into to help me make this more friendly. Should I be returning False? Or 0?

Inside my example/files directory are 3 files which were, for this example, created on the dates specified in the file name:

example/files/randomtext011.201602012.txt

example/files/randomtext011.201602011.txt

example/files/randomtext011.201602013.txt

import os.path
import glob
import datetime

dir = 'example/files'
file_pattern = 'randomtext011.*.txt'

def get_latest_file(file_pattern,path=None):
    if path is None:
        list_of_files = glob.glob('{0}'.format(file_pattern))
        if len(list_of_files)> 0:
            return os.path.split(max(list_of_files, key = os.path.getctime))[1]
    else:
        list_of_files = glob.glob('{0}/{1}'.format(path, file_pattern))
        if len(list_of_files) > 0:
            return os.path.split(max(list_of_files,key=os.path.getctime))[1]
    return False

First of all, I think that your variable names are quite good.


Should I be returning False? Or 0?

I would recommend None

Don't repeat yourself

As you can see, the two branches of your if else are very similar.

Instead you could do a

if path is None:
    fullpath = file_pattern
else:
    fullpath = path + '/' + file_pattern

But joining paths like this is not very pythonic (and might cause problems on windows).

Instead, fullpath = os.path.join(path, file_pattern) is what you are looking for.

About the arguments

You can take inspiration of the os.path.join even further and change the order of your arguments (and completely remove the branching):

def get_latest_file(path, *paths):
    fullpath = os.path.join(path, paths)
    ...
get_latest_file('example', 'files','randomtext011.*.txt')

Use docstrings

And then you might think that the way to call it is not trivial and want to document it: let's use a docstring !

def get_latest_file(path, *paths):
    """Returns the name of the latest (most recent) file 
    of the joined path(s)"""
    fullpath = os.path.join(path, *paths)

Miscellaneous

If you use Python 3, you can use iglob instead.

For the os.path.split, I prefer using it like this (instead of the 1 index):

folder, filename = os.path.split(latest_file)

The import datetime is not used.

Instead of if len(list_of_files)> 0:, you can simply do if list_of_files:

Revised code

def get_latest_file(path, *paths):
    """Returns the name of the latest (most recent) file 
    of the joined path(s)"""
    fullpath = os.path.join(path, *paths)
    list_of_files = glob.glob(fullpath)  # You may use iglob in Python3
    if not list_of_files:                # I prefer using the negation
        return None                      # because it behaves like a shortcut
    latest_file = max(list_of_files, key=os.path.getctime)
    _, filename = os.path.split(latest_file)
    return filename

StackExchange Code Review Q#120494, answer score: 3