Python giving FileNotFoundError for file name returned by os.listdir

I was trying to iterate over the files in a directory like this:

import os

path = r'E:/somedir'

for filename in os.listdir(path):
    f = open(filename, 'r')
    ... # process the file

But Python was throwing FileNotFoundError even though the file exists:

Traceback (most recent call last):
  File "E:/ADMTM/TestT.py", line 6, in <module>
    f = open(filename, 'r')
FileNotFoundError: [Errno 2] No such file or directory: 'foo.txt'

So what is wrong here?

Answers:

Thank you for visiting the Q&A section on Magenaut. Please note that all the answers may not help you solve the issue immediately. So please treat them as advisements. If you found the post helpful (or not), leave a comment & I’ll get back to you as soon as possible.

Method 1

It is because os.listdir does not return the full path to the file, only the filename part; that is 'foo.txt', when open would want 'E:/somedir/foo.txt' because the file does not exist in the current directory.

Use os.path.join to prepend the directory to your filename:

path = r'E:/somedir'

for filename in os.listdir(path):
    with open(os.path.join(path, filename)) as f:
        ... # process the file

(Also, you are not closing the file; the with block will take care of it automatically).

Method 2

os.listdir(directory) returns a list of file names in directory. So unless directory is your current working directory, you need to join those file names with the actual directory to get a proper absolute path:

for filename in os.listdir(path):
    filepath = os.path.join(path, filename)
    f = open(filepath,'r')
    raw = f.read()
    # ...

All methods was sourced from stackoverflow.com or stackexchange.com, is licensed under cc by-sa 2.5, cc by-sa 3.0 and cc by-sa 4.0