Why path is not found in python?
The ~
(tilde) is a shell expansion, not a special "filesystem expansion".
So ~
expands to the current user directly only when found in a shell command:
$echo ~
/home/username
But not if used in the filename passed to python's file objects. The python code:
open('some/file/name')
is equivalent to opening the file 'some/file/name'
in the shell, and I mean literally with the single quotes that prevent expansions included.
So:
open('~/file.txt')
Tries to open:
$echo '~/file.txt'
~/file.txt
And not:
$echo ~/file.txt
/home/username/file.txt
This is stated at the top of the documentation of the os.path
module too:
Unlike a unix shell, Python does not do any automatic path expansions. Functions such as
expanduser()
andexpandvars()
can be invoked explicitly when an application desires shell-like path expansion. (See also theglob
module.)
In fact you can create a file called ~
:
$touch '~'
$ls | grep '~'
~
The single quotes are necessary, because touch ~
would simply execute touch
on /home/username
and no file would be created.
Now if you try to delete it you must escape its name, otherwise the shell will expand it into /home/username
:
$echo ~
/home/username
$rm ~ # translation: "rm: cannot remove "/home/username": It's a directory"
rm: impossibile rimuovere "/home/username": È una directory
$rm '~' # proper way to delete it
If you want to expand the ~
in filenames use the os.path.expanduser
function:
>>> import os.path
>>> os.path.expanduser('~/file.txt')
'/home/username/file.txt'
Note that realpath
and abspath
do not expand the ~
:
>>> os.path.realpath('~/file.txt')
'/home/username/~/file.txt'
>>> os.path.abspath('~/file.txt')
'/home/username/~/file.txt'
So, if you want to be sure to convert a pathname given by the user in "shell language"1 into an absolute path usable with python's file objects you should do:
os.path.abspath(os.path.expanduser(path))
1 Not saying sh
/bash
because they are cross platform.
Jim Blum
Updated on June 04, 2022Comments
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Jim Blum almost 2 years
I am trying to open a file that exists using python, and opens perfectly if I open it using gedit in command line.
However, I get the following error message:
andreas@ubuntu:~/Desktop/Thesis/Codes/ModifiedFiles$ python vis.py -f myoutputcsv.csv Matplotlib version 1.3.1 Traceback (most recent call last): File "vis.py", line 1082, in <module> reliability_table = ReliabilityTable(reliability_table_file) File "vis.py", line 112, in __init__ self.read(filename) File "vis.py", line 139, in read self.data = genfromtxt(filename, delimiter=',',comments='#', dtype=float) File "/usr/lib/python2.7/dist-packages/numpy/lib/npyio.py", line 1344, in genfromtxt fhd = iter(np.lib._datasource.open(fname, 'rbU')) File "/usr/lib/python2.7/dist-packages/numpy/lib/_datasource.py", line 147, in open return ds.open(path, mode) File "/usr/lib/python2.7/dist-packages/numpy/lib/_datasource.py", line 496, in open raise IOError("%s not found." % path) IOError: ~/Desktop/Thesis/Codes/ModifiedFiles/reliability_table_2.csv not found.
Do you know what I may be doing wrong? I have very little experience with python and I cannot find the reason the file opens at command line but not using python.
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Jim Blum almost 10 yearsThanks a lot Bakariu!!! Yes, this is exactly what I had done :) Excellent answer!