I am trying to learn python and am making a program that will output a script. I want to use os.path.join, but am pretty confused. According to the docs if I say:
os.path.join('c:', 'sourcedir')
I get "C:sourcedir". According to the docs, this is normal, right?
But when I use the copytree command, Python will output it the desired way, for example:
import shutil
src = os.path.join('c:', 'src')
dst = os.path.join('c:', 'dst')
shutil.copytree(src, dst)
Here is the error code I get:
WindowsError: [Error 3] The system cannot find the path specified: 'C:src/*.*'
If I wrap the os.path.join with os.path.normpath I get the same error.
If this os.path.join can’t be used this way, then I am confused as to its purpose.
According to the pages suggested by Stack Overflow, slashes should not be used in join—that is correct, I assume?
Answers:
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Method 1
To be even more pedantic, the most python doc consistent answer would be:
mypath = os.path.join('c:', os.sep, 'sourcedir')
Since you also need os.sep for the posix root path:
mypath = os.path.join(os.sep, 'usr', 'lib')
Method 2
Windows has a concept of current directory for each drive. Because of that, "c:sourcedir" means “sourcedir” inside the current C: directory, and you’ll need to specify an absolute directory.
Any of these should work and give the same result, but I don’t have a Windows VM fired up at the moment to double check:
"c:/sourcedir"
os.path.join("/", "c:", "sourcedir")
os.path.join("c:/", "sourcedir")
Method 3
To be pedantic, it’s probably not good to hardcode either / or as the path separator. Maybe this would be best?
mypath = os.path.join('c:%s' % os.sep, 'sourcedir')
or
mypath = os.path.join('c:' + os.sep, 'sourcedir')
Method 4
For a system-agnostic solution that works on both Windows and Linux, no matter what the input path, one could use os.path.join(os.sep, rootdir + os.sep, targetdir)
On WIndows:
>>> os.path.join(os.sep, "C:" + os.sep, "Windows") 'C:\Windows'
On Linux:
>>> os.path.join(os.sep, "usr" + os.sep, "lib") '/usr/lib'
Method 5
The reason os.path.join('C:', 'src') is not working as you expect is because of something in the documentation that you linked to:
Note that on Windows, since there is a
current directory for each drive,
os.path.join(“c:”, “foo”) represents a
path relative to the current directory
on drive C: (c:foo), not c:foo.
As ghostdog said, you probably want mypath=os.path.join('c:\', 'sourcedir')
Method 6
I’d say this is a (windows)python bug.
Why bug?
I think this statement should be True
os.path.join(*os.path.dirname(os.path.abspath(__file__)).split(os.path.sep))==os.path.dirname(os.path.abspath(__file__))
But it is False on windows machines.
Method 7
to join a windows path, try
mypath=os.path.join('c:\', 'sourcedir')
basically, you will need to escape the slash
Method 8
You have a few possible approaches to treat path on Windows, from the most hardcoded ones (as using raw string literals or escaping backslashes) to the least ones. Here follows a few examples that will work as expected. Use what better fits your needs.
In[1]: from os.path import join, isdir
In[2]: from os import sep
In[3]: isdir(join("c:", "\", "Users"))
Out[3]: True
In[4]: isdir(join("c:", "/", "Users"))
Out[4]: True
In[5]: isdir(join("c:", sep, "Users"))
Out[5]: True
Method 9
Consent with @georg-
I would say then why we need lame os.path.join– better to use str.join or unicode.join e.g.
sys.path.append('{0}'.join(os.path.dirname(__file__).split(os.path.sep)[0:-1]).format(os.path.sep))
Method 10
answering to your comment : “the others ‘//’ ‘c:’, ‘c:\’ did not work (C:\ created two backslashes, C: didn’t work at all)”
On windows using
os.path.join('c:', 'sourcedir')
will automatically add two backslashes \ in front of sourcedir.
To resolve the path, as python works on windows also with forward slashes -> ‘/’, simply add .replace('\','/') with os.path.join as below:-
os.path.join('c:\', 'sourcedir').replace('\','/')
e.g: os.path.join('c:\', 'temp').replace('\','/')
output : ‘C:/temp’
Method 11
The proposed solutions are interesting and offer a good reference, however they are only partially satisfying. It is ok to manually add the separator when you have a single specific case or you know the format of the input string, but there can be cases where you want to do it programmatically on generic inputs.
With a bit of experimenting, I believe the criteria is that the path delimiter is not added if the first segment is a drive letter, meaning a single letter followed by a colon, no matter if it corresponds to a real unit.
For example:
import os
testval = ['c:','c:\','d:','j:','jr:','data:']
for t in testval:
print ('test value: ',t,', join to "folder"',os.path.join(t,'folder'))
test value: c: , join to "folder" c:folder test value: c: , join to "folder" c:folder test value: d: , join to "folder" d:folder test value: j: , join to "folder" j:folder test value: jr: , join to "folder" jr:folder test value: data: , join to "folder" data:folder
A convenient way to test for the criteria and apply a path correction can be to use os.path.splitdrive comparing the first returned element to the test value, like t+os.path.sep if os.path.splitdrive(t)[0]==t else t.
Test:
for t in testval:
corrected = t+os.path.sep if os.path.splitdrive(t)[0]==t else t
print ('original: %stcorrected: %s'%(t,corrected),' join corrected->',os.path.join(corrected,'folder'))
original: c: corrected: c: join corrected-> c:folder original: c: corrected: c: join corrected-> c:folder original: d: corrected: d: join corrected-> d:folder original: j: corrected: j: join corrected-> j:folder original: jr: corrected: jr: join corrected-> jr:folder original: data: corrected: data: join corrected-> data:folder
it can be probably be improved to be more robust for trailing spaces, and I have tested it only on windows, but I hope it gives an idea.
See also Os.path : can you explain this behavior? for interesting details on systems other then windows.
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