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executing python scripts that are symlinked

+1 vote
24 views

How can I say, from the cmd line, that python should take my CWD as my CWD, and not the directory where the script actually is?

I have a python script that works fine when it sits in directory WC, but if I move it out of WC to H and put a symlink from H/script to WC, it doesn't find the packages that are in WC. Also, if I use the
absolute path to H, it won't find them, but I guess I can understand that.

Someone said on the net that python doesn't know whether a file is real or a symlink, but I think that somehow, python is able to find out where the real file is and treat that as its base of operations.

posted May 16, 2013 by anonymous

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2 Answers

+1 vote
 
Best answer

Python does use your current working directory as your current working directory. I think you are misdiagnosing the problem.

Here's a demonstration:

$ cat test.py
import os
print os.getcwd()

$ ln -s ~/test.py /tmp/test
$ ls -l /tmp/test 
lrwxrwxrwx 1 ...    ... 19 May 16 18:58 /tmp/test -> /home/steve/test.py
$ cd /etc/
$ python /tmp/test 
/etc

The obvious solution is to make sure that WC is in the Python path. You can do that by adding it the environment variable PYTHONPATH, or by adding it to sys.path at the start of your script. I think you can also use a .pth file as well.

Another solution may be to add this to the beginning of your script:

os.setcwd('path/to/WC')

but that's a crappy solution, you generally don't want to be changing the working directory from inside scripts if you can avoid it.

answer May 16, 2013 by anonymous
0 votes

Symlinks can find their targets, but targets have absolutely no way of knowing where symlinks to them are. It's one-way. It would work if the actual file were in WC and you created a symlink inside H.

answer May 16, 2013 by anonymous
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my code is-

i = 0
for i in range(1000):
 try:
 with open('filename%d.%d.%d.json'%(0,0,i,)): pass
 continue
 except IOError:
 dataFile = file('filename%d.%d.%d.json'%(0,0,i,), 'a+')
 break

But It will take more time after creating many files, So i want to store value of last var "i" in a variable so that when I run my script again then I can use it. for example-
my last created file is filename0.0.27 then it should store 27 in a variable and when i run again then new file should be created 0.0.28 according to last value "27", so that i could save time and it can create file fast..


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