I discovered that a script's "current working directory" is, initially, not the where the script is located, but rather where the user is when he/she runs the script.
If the script is at /Desktop/Projects/pythonProject/myscript.py, but I'm at /Documents/Arbitrary in my terminal when I run the script, then that's going to be it's present working directory, and an attempt at open('data.txt') is going to give File Not Found because it's not looking in the right directory.
So how is a script supposed to open files if it can't know where it's being run from? How is this handled?
My initial thought was to use absolute paths. Say my script needs to open data.txt which is stored alongside it in its package pythonProject. Then I would just say open('/Desktop/Projects/pythonProject/data.txt').
But then you can't ever move the project without editing every path in it, so this can't be the right solution.
Or is the answer simply that you must be in the directory where the script is located whenever you run the script? That doesn't seem right either.
Is there some simple manipulation for this that I'm not thinking of? Are you just supposed to os.chdir to the script's location at the beginning of the script?
Get the current file's directory path, using os.path.dirname, os.path.abspath, os.path.realpath, and the __file__ variable:
import os
file_dir = os.path.dirname(os.path.abspath(os.path.realpath(__file__)))
Then, to create cross-platform filepaths, use os.path.join():
os.path.join(file_dir, "test.txt")
Alternatively, you can change the current working directory to the running file's directory so you don't have to os.path.join every time:
os.path.chdir(os.path.dirname(os.path.abspath(os.path.realpath(__file__))))
Why use os.path.abspath and os.path.realpath? The inner realpath resolves symbolic links, while the abspath resolves relative paths. If you know for sure no symbolic links are being used, you can omit this inner realpath call.
A module's location is always available in the __file__ variable. You can use the functions in os.path (I'm mainly thinking of basedir and join) to transform module-relative paths to absolute paths
Related
I am trying to open the file recentlyUpdated.yaml from my Python script. But when I try using:
open('recentlyUpdated.yaml')
I get an error that says:
IOError: [Errno 2] No such file or directory: 'recentlyUpdated.yaml'
Why? How can I fix the problem?
Ensure the file exists (and has the right file extension): use os.listdir() to see the list of files in the current working directory.
Ensure you're in the expected directory using os.getcwd().
(If you launch your code from an IDE, you may be in a different directory.)
You can then either:
Call os.chdir(dir) where dir is the directory containing the file. Then, open the file using just its name, e.g. open("file.txt").
Specify an absolute path to the file in your open call.
Use a raw string (r"") 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
Most likely, the problem is that you're using a relative file path to open the file, but the current working directory isn't set to what you think it is.
It's a common misconception that relative paths are relative to the location of the python script, but this is untrue. Relative file paths are always relative to the current working directory, and the current working directory doesn't have to be the location of your python script.
You have three options:
Use an absolute path to open the file:
file = open(r'C:\path\to\your\file.yaml')
Generate the path to the file relative to your python script:
from pathlib import Path
script_location = Path(__file__).absolute().parent
file_location = script_location / 'file.yaml'
file = file_location.open()
(See also: How do I get the path and name of the file that is currently executing?)
Change the current working directory before opening the file:
import os
os.chdir(r'C:\path\to\your\file')
file = open('file.yaml')
Other common mistakes that could cause a "file not found" error include:
Accidentally using escape sequences in a file path:
path = 'C:\Users\newton\file.yaml'
# Incorrect! The '\n' in 'Users\newton' is a line break character!
To avoid making this mistake, remember to use raw string literals for file paths:
path = r'C:\Users\newton\file.yaml'
# Correct!
(See also: Windows path in Python)
Forgetting that Windows doesn't display file extensions:
Since Windows doesn't display known file extensions, sometimes when you think your file is named file.yaml, it's actually named file.yaml.yaml. Double-check your file's extension.
The file may be existing but may have a different path. Try writing the absolute path for the file.
Try os.listdir() function to check that atleast python sees the file.
Try it like this:
file1 = open(r'Drive:\Dir\recentlyUpdated.yaml')
Possibly, you closed the 'file1'.
Just use 'w' flag, that create new file:
file1 = open('recentlyUpdated.yaml', 'w')
mode is an optional string that specifies the mode in which the file
is opened. It defaults to 'r' which means open for reading in text
mode. Other common values are 'w' for writing (truncating the file if
it already exists)...
(see also https://docs.python.org/3/library/functions.html?highlight=open#open)
If is VSCode see the workspace. If you are in other workspace this error can rise
Understanding absolute and relative paths
The term path means exactly what it sounds like. It shows the steps that need to be taken, into and out of folders, to find a file. Each step on the path is either a folder name, the special name . (which means the current folder), or the special name .. (which means to go back/out into the parent folder).
The terms absolute and relative also have their usual English meaning. A relative path shows where something is relative to some start point; an absolute path is a location starting from the top.
Paths that start with a path separator, or a drive letter followed by a path separator (like C:/foo) on Windows, are absolute. (On Windows there are also UNC paths, which are necessarily absolute. Most people will never have to worry about these.)
Paths that directly start with a file or folder name, or a drive letter followed directly by the file or folder name (like C:foo) on Windows, are relative.
Understanding the "current working directory"
Relative paths are "relative to" the so-called current working directory (hereafter abbreviated CWD). At the command line, Linux and Mac use a common CWD across all drives. (The entire file system has a common "root", and may include multiple physical storage devices.) Windows is a bit different: it remembers the most recent CWD for each drive, and has separate functionality to switch between drives, restoring those old CWD values.
Each process (this includes terminal/command windows) has its own CWD. When a program is started from the command line, it will get the CWD that the terminal/command process was using. When a program is started from a GUI (by double-clicking a script, or dragging something onto the script, or dragging the script onto a Python executable) or by using an IDE, the CWD might be any number of things depending on the details.
Importantly, the CWD is not necessarily where the script is located.
The script's CWD can be checked using os.getcwd, and modified using os.chdir. Each IDE has its own rules that control the initial CWD; check the documentation for details.
To set the CWD to the folder that contains the current script, determine that path and then set it:
os.chdir(os.path.dirname(os.path.abspath(__file__)))
Verifying the actual file name and path
There are many reasons why the path to a file might not match expectations. For example, sometimes people expect C:/foo.txt on Windows to mean "the file named foo.txt on the desktop". This is wrong. That file is actually - normally - at C:/Users/name/Desktop/foo.txt (replacing name with the current user's username). It could instead be elsewhere, if Windows is configured to put it elsewhere. To find the path to the desktop in a portable way, see How to get Desktop location?.
It's also common to mis-count ..s in a relative path, or inappropriately repeat a folder name in a path. Take special care when constructing a path programmatically. Finally, keep in mind that .. will have no effect while already in a root directory (/ on Linux or Mac, or a drive root on Windows).
Take even more special care when constructing a path based on user input. If the input is not sanitized, bad things could happen (e.g. allowing the user to unzip a file into a folder where it will overwrite something important, or where the user ought not be allowed to write files).
Another common gotcha is that the special ~ shortcut for the current user's home directory does not work in an absolute path specified in a Python program. That part of the path must be explicitly converted to the actual path, using os.path.expanduser. See Why am I forced to os.path.expanduser in python? and os.makedirs doesn't understand "~" in my path.
Keep in mind that os.listdir will give only the file names, not paths. Trying to iterate over a directory listed this way will only work if that directory is the current working directory.
It's also important to make sure of the actual file name. Windows has an option to hide file name extensions in the GUI. If you see foo.txt in a window, it could be that the file's actual name is foo.txt.txt, or something else. You can disable this option in your settings. You can also verify the file name using the command line; dir will tell you the truth about what is in the folder. (The Linux/Mac equivalent is ls, of course; but the problem should not arise there in the first place.)
Backslashes in ordinary strings are escape sequences. This causes problems when trying to a backslash as the path separator on Windows. However, using backslashes for this is not necessary, and generally not advisable. See Windows path in Python.
When trying to create a new file using a file mode like w, the path to the new file still needs to exist - i.e., all the intervening folders. See for example Trying to use open(filename, 'w' ) gives IOError: [Errno 2] No such file or directory if directory doesn't exist. Also keep in mind that the new file name has to be valid. In particular, it will not work to try to insert a date in MM/DD/YYYY format into the file name, because the /s will be treated as path separators.
Check the path that has been mentioned, if it's absolute or relative.
If its something like-->/folder/subfolder/file -->Computer will search for folder in root directory.
If its something like--> ./folder/subfolder/file --> Computer will search for folder in current working directory.
If you are using IDE like VScode, make sure you have opened the IDE from the same directory where you have kept the file you want to access.
For example, if you want to access file.txt which is inside the Document, try opening the IDE from Document by right clicking in the directory and clicking "Open with "
When I am using Absolute path the code is working fine but using relative path throwing FileNotFoundError in python.
f = open("Input.txt","r")
Your python file is executed by the terminal. You can clearly see that your terminal is at the folder ...Desktop\cs\Python\myproject\. Since the file "Input.txt" does not exist relative to the path of your terminal, you are getting this error. (That is, the path ...Desktop\cs\Python\myproject\Input.txt does not exist)
A simple solution would be to use absolute path in your python file instead of the relative path.
Another cheap solution is to use the terminal, go to the correct folder and run your file, as intended by God.
If you really want to dedicate a single button for running, you can try the following:
EDIT: Okay, I understand you are using the "Run button" at top of python files to run.
You only need to set the setting python.terminal.executeInFileDir to true.
In Settings, search for python.terminal.executeInFileDir and mark it. That should be what you need.
A quick solution to use relative paths can be to right click on the file, copy relative path and replace "" with "/". You can do it manually or with the function .replace("","/").
"route\input.txt".replace("","/")
I am trying to open the file recentlyUpdated.yaml from my Python script. But when I try using:
open('recentlyUpdated.yaml')
I get an error that says:
IOError: [Errno 2] No such file or directory: 'recentlyUpdated.yaml'
Why? How can I fix the problem?
Ensure the file exists (and has the right file extension): use os.listdir() to see the list of files in the current working directory.
Ensure you're in the expected directory using os.getcwd().
(If you launch your code from an IDE, you may be in a different directory.)
You can then either:
Call os.chdir(dir) where dir is the directory containing the file. Then, open the file using just its name, e.g. open("file.txt").
Specify an absolute path to the file in your open call.
Use a raw string (r"") 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
Most likely, the problem is that you're using a relative file path to open the file, but the current working directory isn't set to what you think it is.
It's a common misconception that relative paths are relative to the location of the python script, but this is untrue. Relative file paths are always relative to the current working directory, and the current working directory doesn't have to be the location of your python script.
You have three options:
Use an absolute path to open the file:
file = open(r'C:\path\to\your\file.yaml')
Generate the path to the file relative to your python script:
from pathlib import Path
script_location = Path(__file__).absolute().parent
file_location = script_location / 'file.yaml'
file = file_location.open()
(See also: How do I get the path and name of the file that is currently executing?)
Change the current working directory before opening the file:
import os
os.chdir(r'C:\path\to\your\file')
file = open('file.yaml')
Other common mistakes that could cause a "file not found" error include:
Accidentally using escape sequences in a file path:
path = 'C:\Users\newton\file.yaml'
# Incorrect! The '\n' in 'Users\newton' is a line break character!
To avoid making this mistake, remember to use raw string literals for file paths:
path = r'C:\Users\newton\file.yaml'
# Correct!
(See also: Windows path in Python)
Forgetting that Windows doesn't display file extensions:
Since Windows doesn't display known file extensions, sometimes when you think your file is named file.yaml, it's actually named file.yaml.yaml. Double-check your file's extension.
The file may be existing but may have a different path. Try writing the absolute path for the file.
Try os.listdir() function to check that atleast python sees the file.
Try it like this:
file1 = open(r'Drive:\Dir\recentlyUpdated.yaml')
Possibly, you closed the 'file1'.
Just use 'w' flag, that create new file:
file1 = open('recentlyUpdated.yaml', 'w')
mode is an optional string that specifies the mode in which the file
is opened. It defaults to 'r' which means open for reading in text
mode. Other common values are 'w' for writing (truncating the file if
it already exists)...
(see also https://docs.python.org/3/library/functions.html?highlight=open#open)
If is VSCode see the workspace. If you are in other workspace this error can rise
Understanding absolute and relative paths
The term path means exactly what it sounds like. It shows the steps that need to be taken, into and out of folders, to find a file. Each step on the path is either a folder name, the special name . (which means the current folder), or the special name .. (which means to go back/out into the parent folder).
The terms absolute and relative also have their usual English meaning. A relative path shows where something is relative to some start point; an absolute path is a location starting from the top.
Paths that start with a path separator, or a drive letter followed by a path separator (like C:/foo) on Windows, are absolute. (On Windows there are also UNC paths, which are necessarily absolute. Most people will never have to worry about these.)
Paths that directly start with a file or folder name, or a drive letter followed directly by the file or folder name (like C:foo) on Windows, are relative.
Understanding the "current working directory"
Relative paths are "relative to" the so-called current working directory (hereafter abbreviated CWD). At the command line, Linux and Mac use a common CWD across all drives. (The entire file system has a common "root", and may include multiple physical storage devices.) Windows is a bit different: it remembers the most recent CWD for each drive, and has separate functionality to switch between drives, restoring those old CWD values.
Each process (this includes terminal/command windows) has its own CWD. When a program is started from the command line, it will get the CWD that the terminal/command process was using. When a program is started from a GUI (by double-clicking a script, or dragging something onto the script, or dragging the script onto a Python executable) or by using an IDE, the CWD might be any number of things depending on the details.
Importantly, the CWD is not necessarily where the script is located.
The script's CWD can be checked using os.getcwd, and modified using os.chdir. Each IDE has its own rules that control the initial CWD; check the documentation for details.
To set the CWD to the folder that contains the current script, determine that path and then set it:
os.chdir(os.path.dirname(os.path.abspath(__file__)))
Verifying the actual file name and path
There are many reasons why the path to a file might not match expectations. For example, sometimes people expect C:/foo.txt on Windows to mean "the file named foo.txt on the desktop". This is wrong. That file is actually - normally - at C:/Users/name/Desktop/foo.txt (replacing name with the current user's username). It could instead be elsewhere, if Windows is configured to put it elsewhere. To find the path to the desktop in a portable way, see How to get Desktop location?.
It's also common to mis-count ..s in a relative path, or inappropriately repeat a folder name in a path. Take special care when constructing a path programmatically. Finally, keep in mind that .. will have no effect while already in a root directory (/ on Linux or Mac, or a drive root on Windows).
Take even more special care when constructing a path based on user input. If the input is not sanitized, bad things could happen (e.g. allowing the user to unzip a file into a folder where it will overwrite something important, or where the user ought not be allowed to write files).
Another common gotcha is that the special ~ shortcut for the current user's home directory does not work in an absolute path specified in a Python program. That part of the path must be explicitly converted to the actual path, using os.path.expanduser. See Why am I forced to os.path.expanduser in python? and os.makedirs doesn't understand "~" in my path.
Keep in mind that os.listdir will give only the file names, not paths. Trying to iterate over a directory listed this way will only work if that directory is the current working directory.
It's also important to make sure of the actual file name. Windows has an option to hide file name extensions in the GUI. If you see foo.txt in a window, it could be that the file's actual name is foo.txt.txt, or something else. You can disable this option in your settings. You can also verify the file name using the command line; dir will tell you the truth about what is in the folder. (The Linux/Mac equivalent is ls, of course; but the problem should not arise there in the first place.)
Backslashes in ordinary strings are escape sequences. This causes problems when trying to a backslash as the path separator on Windows. However, using backslashes for this is not necessary, and generally not advisable. See Windows path in Python.
When trying to create a new file using a file mode like w, the path to the new file still needs to exist - i.e., all the intervening folders. See for example Trying to use open(filename, 'w' ) gives IOError: [Errno 2] No such file or directory if directory doesn't exist. Also keep in mind that the new file name has to be valid. In particular, it will not work to try to insert a date in MM/DD/YYYY format into the file name, because the /s will be treated as path separators.
Check the path that has been mentioned, if it's absolute or relative.
If its something like-->/folder/subfolder/file -->Computer will search for folder in root directory.
If its something like--> ./folder/subfolder/file --> Computer will search for folder in current working directory.
If you are using IDE like VScode, make sure you have opened the IDE from the same directory where you have kept the file you want to access.
For example, if you want to access file.txt which is inside the Document, try opening the IDE from Document by right clicking in the directory and clicking "Open with "
I realise this question may already exist, but the answers I've found haven't worked and I have a slightly different setup.
I have a python file /home/pi/python_games/frontend.py that I am trying to start when lxde loads by placing #python /home/pi/python_games/frontend.py in /etc/xdg/lxsession/LXDE/autostart.
It doesn't run and there are no error messages.
When trying to run python /home/pi/python_games/frontend.py, python complains about not being able to find the files that are loaded using relative links eg: /home/pi/python_games/image.png is called with image.png. Obviously one solution would be to give these resources absolute paths, but the python program also calls other python programs in its directory that also have relative paths, and I don't want to go changing all them.
Anyone got any ideas?
Thanks
Tom
you could change your current working directory inside the script before you start calling your relative imports, use os.chdir("absolute path on where your script lives").
Rather than change your current working directory, in yourfrontend.pyscript you could use the value of the predefined__file__module attribute, which will be the absolute pathname of the script file, to determine absolute paths to the other files in the same directory.
Functions in theos.pathmodule, such assplit()andjoin(), will make doing this fairly easy.
My script.py creates a temporary file using a relative path.
When running it as:
python script.py
it works as expected.
But it doesn't work when you run it like:
python /path/to/script.py
The problem is that I don't know which path it will be running in. How can I get the absolute path to the script folder (the "/path/to") so the temporary file can be created in the same directory as the script?
What about the following?
os.path.abspath(os.path.dirname(__file__))
Per the great Dive Into Python:
import sys, os
print 'sys.argv[0] =', sys.argv[0] 1
pathname = os.path.dirname(sys.argv[0]) 2
print 'path =', pathname
print 'full path =', os.path.abspath(pathname)
The two current answers reflect the ambiguity of your question.
When you've run python /path/to/script.py, where do you want your tempfile? In the current directory (./tempfile.txt) or in /path/to/tempfile.txt?
If the former, you can simply use the relative path (or, for weird and arcane purposes, get the absolute path equivalent to the current directory as #Desintegr suggests, with os.getcwd).
If the latter, you can learn exactly how the script was invoked with sys.argv[0], as #Jonathan suggests, and manipulate that path with the functions in os.path (of course you can also apply those functions to what os.getcwd returns, if the former case applies), or work with os.path.dirname(__file__) and the like (the latter's necessary if you want this latter behavior also when the script is imported as a module, not just when it's run as a main script).
You can use the os.getcwd() method to know the current working directory.
Return a string representing the current working directory.
Availability: Unix, Windows.
You can use the os.chdir(path) method to change the current working directory.
Change the current working directory to path.
Availability: Unix, Windows.