Open() Gives Filenotfounderror/Ioerror: Errno 2 No Such File or Directory

open() gives FileNotFoundError/IOError: Errno 2 No such file or directory

• Make sure the file exists: use os.listdir() to see the list of files in the current working directory
• Make sure you're in the directory you think you're in with os.getcwd() (if you launch your code from an IDE, you may well be in a different directory)
• You can then either:
  
  • Call os.chdir(dir), dir being the folder where the file is
    located, then open the file with just its name like you were doing.
  • Specify an absolute path to the file in your open call.
• Remember to use a raw string if your path uses backslashes, like
  so: dir = r'C:\Python32'
  
  • If you don't use raw-string, you have to escape every backslash: 'C:\\User\\Bob\\...'
  • Forward-slashes also work on Windows 'C:/Python32' and do not need to be escaped.

Let me clarify how Python finds files:

• An absolute path is a path that starts with your computer's root directory, for example C:\Python\scripts if you're on Windows.
• A relative path is a path that does not start with your computer's root directory, and is instead relative to something called the working directory. You can view Python's current working directory by calling os.getcwd().

If you try to do open('sortedLists.yaml'), Python will see that you are passing it a relative path, so it will search for the file inside the current working directory.

Calling os.chdir() will change the current working directory.

Example: Let's say file.txt is found in C:\Folder.

To open it, you can do:

os.chdir(r'C:\Folder')
open('file.txt') # relative path, looks inside the current working directory

or

open(r'C:\Folder\file.txt') # absolute path

Getting error: FileNotFoundError: [Errno 2] No such file or directory when using Python open()

You can use glob, i.e.:

from glob import glob

p = "/path/to/*.txt"
for t in glob(p):
    with open(t) as f:
        text = f.read()
    # do something with text

Trying to use open(filename, 'w' ) gives IOError: [Errno 2] No such file or directory if directory doesn't exist

You are correct in surmising that the parent directory for the file must exist in order for open to succeed. The simple way to deal with this is to make a call to os.makedirs.

From the documentation:

os.makedirs(path[, mode])

Recursive directory creation function. Like mkdir(), but makes all intermediate-level directories needed to contain the leaf directory.

So your code might run something like this:

filename = ...
dirname = os.path.dirname(filename)
if not os.path.exists(dirname):
    os.makedirs(dirname)
with open(filename, 'w'):
    ...

open file in w mode: IOError: [Errno 2] No such file or directory

You'll see this error if the directory containing the file you're trying to open does not exist, even when trying to open the file in w mode.

Since you're opening the file with a relative path, it's possible that you're confused about exactly what that directory is. Try putting a quick print to check:

import os

curpath = os.path.abspath(os.curdir)
packet_file = "%s/%s/%s/%s.mol2" % ("dir", "dir2", "dir3", "some_file")
print "Current path is: %s" % (curpath)
print "Trying to open: %s" % (os.path.join(curpath, packet_file))

packetFile = open(packet_file, "w")

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