the slash & Windows paths

Mon Dec 19 22:29:00 EST 2011

On Mon, 19 Dec 2011 15:02:50 -0700, Juan Declet-Barreto wrote:

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[many more lines of rubbish deleted]

Please do not post HTML code (wrongly called "rich text") emails here, as 
the news group is text only.

Extracting your actual question:

> All,
> 
> I have a Windows-style path that I need to modify so Python functions
> can find it. For example, the path
> "C:\Projects\Population_Pyramids\charts\test.xls" is being interpreted
> as pointing to a file called "est.xls" since the "t" is being escaped by
> the preceding slash as a tab.

It almost certainly is not. The path does not contain a backslash t, it 
contains a tab. The escape occurs before the string is built.

When you write s = "abc", the quotation marks are not part of the string. 
They are part of the string display: delimiters of the string, not part 
of it.

Similarly, when you write s = "\t", there are no quotation marks in the 
string, and no backslash, and no "t". There is only a single character, 
tab. So the above path is identical to you writing:

"C:\Projects\Population_Pyramids\charts" + ord(9) + "est.xls" 

To fix this, the best solution is to take advantage that Windows accepts 
both forward and back slashes as directory separators:

"C:/Projects/Population_Pyramids/charts/test.xls" 

Or you can build the string from components, and use os.path.join() to 
build the complete string.

Or you can use raw strings as described:

> I know this is straightforward to handle using raw literals by prefixing
> the literal with an 'r', but my path is stored in a variable.

It doesn't matter whether path is stored in a variable or not. When you 
build a string as a literal in source code, backslashes are always 
escaped. If you read text from external data, like a file, they are never 
escaped.

> My questions are: 1. How do I prevent single slashes from being escaped
> in a string variable (NOT literal)?

Backslashes are not interpreted especially in string variables. They are 
only interpreted as backslashes when in source code. Compare the 
difference:

>>> s = "this \n is a newline"  # a string literal as source code
>>> print(s)
this 
 is a newline
>>> s = input("Enter text with an escape:")  # data read from the user
Enter text with an escape:this \n is a newline
>>> print(s)
this \n is a newline

If you are reading the paths from a config file, they will not be 
interpreted. If you are building the paths from components, like this:

folders = ['a', 'b', 'c']
os.path.join(folders)

you should get a\b\c. (I can't test this, because I am not using Windows, 
so I will get something different.)

Or, best solution, take advantage that Windows accepts both back slashes 
and forward slashes in path names, and always use forward slashes.

-- 
Steven