Arcpy changing current working directory

Question

I can't seem to understand the following behaviour:
mxd = ur'G:\MapImageCreator\ImageTaker.mxd'

print os.getcwd()                          # C:\Documents and Settings\dabkowsk\Desktop (where I run the script from)
mxd = arcpy.mapping.MapDocument(mxd)
print os.getcwd()                          # G:\MapImageCreator

Why does creating a MapDocument object change my working directory? This way I can't use any relative path in my entire script. For example, if I describe an output file as just 'abcdefg.txt', it gets created in the mxd's directory, not in the one I run the script from.

markdenil · Answer

relying on environment settings that can change unexpectedly is not a safe practice.
If you can get the path parameters set as you need at the outset, 
you can then capture the paths to variables and use the variables to give explicit paths.

That way, Arc and the system can switch between 'current' directories all day, but you have already 
captured the locations for later use

for example:
scriptHome = os.getcwd()

GrzegorzDabkowski · Answer

To wrap this up, documentation  says as follows:You cannot type relative paths (using the dot and double-dot notation) in any ArcGIS application. Nor can you use relative paths in Python scripts.

I decided to explicitly transform all input relative paths to absolute ones at the beginning of the script, before any arcpy method uses them. It's certainly not convenient not to be able to use relative paths, especially if some interactive use is envisaged, but it seems that's just a limitation of the environment.

GrzegorzDabkowski · Answer

I added a line setting arcpy.env.workspace, but that didn't change anything.