For Mac/Linux;

PYTHONPATH=/foo/bar/baz python somescript.py somecommand

For Windows, setup a wrapper pythonpath.bat;

@ECHO OFF
setlocal
set PYTHONPATH=%1
python %2 %3
endlocal

and call pythonpath.bat script file like;

pythonpath.bat /foo/bar/baz somescript.py somecommand

You know what has worked for me really well on windows.

My Computer > Properties > Advanced System Settings > Environment Variables >

Just add the path as C:\Python27 (or wherever you installed python)

OR

Then under system variables I create a new Variable called PythonPath. In this variable I have C:\Python27\Lib;C:\Python27\DLLs;C:\Python27\Lib\lib-tk;C:\other-folders-on-the-path

This is the best way that has worked for me which I hadn't found in any of the docs offered.

EDIT: For those who are not able to get it, Please add

C:\Python27;

along with it. Else it will never work.

You don't set PYTHONPATH, you add entries to sys.path. It's a list of directories that should be searched for Python packages, so you can just append your directories to that list.

import sys

sys.path.append('/path/to/whatever')

In fact, sys.path is initialized by splitting the value of PYTHONPATH on the path separator character (: on Linux-like systems, ; on Windows).

You can also add directories using site.addsitedir, and that method will also take into account .pth files existing within the directories you pass. (That would not be the case with directories you specify in PYTHONPATH.)

py.exe is the Python Launcher for Windows and is a separate program from any given python.exe. However, its intended purpose is to allow multiple versions of Python to be ran with minimal fuss. So, for instance, if you hypothetically needed to run Python 2.7 or Python 3.6, you could just use something like e.g. py -2.7 or py -3.6 (assuming both were versions which were installed and recognized on your system).

But for some of my programs I need to use python in order to be able to run my code.

If you really wish to use a single version of Python from the command line, simply add the folder where your prefered python.exe resides to your PATH/Path variable(s).

On Windows 7:

• Go to Control Panel\System and Security\System.

• Click the Advanced system settings link.

• Select the Advanced tab from the System Properties dialog box and click the Environment Variables... button.

• Edit your PATH (User) and/or Path (System) variables to include e.g. C:\path\to\your\preferred\python.exe (remember to put a ; at the end of the last listed path before putting the path to your python.exe).

• Click OK when finished.

In Windows 10, you can:

• Search for the Control Panel from the Start Menu.

  Or you can:

• Search for env from the Start Menu and click the link to edit your environment variables.

• You will still need to click the Environment Variables... button in either case under the Advanced tab from the System Properties dialog box.

• Click Edit and add your C:\path\to\your\preferred\python.exe path to the appropriate PATH (User) and/or Path (System) variable list.

• Click OK when finished.

python should now be available from the command line. If you are still having trouble running it, you may need to log out and then log back in (rebooting is typically unnecessary).

"Python" As A Batch File

While a bit of a hack, you can also "alias" py.exe as python with a batch file.

Create a new .txt file and and put e.g.:

C:\path\to\your\py.exe %*

Save it and rename it to python.bat.

Then place this batch file in your PATH\Path variable(s), as above (ex. as C:\path\to\your\python.bat).

In this case, you're still using py.exe in the background but using python (a.k.a. python.bat) to call it. The %* notation allows any variables (e.g. script names, options, etc.) to be passed along automatically to py.exe.

To be clear, you can simply use python from the command line with this method. You do not need to use python.bat.

As a final, final note, while not recommended, you could also probably simply change the name of py.exe to python.exe if you really wanted to.

Try appending to PYTHONPATH instead of overwriting it completely.

export PYTHONPATH=$PYTHONPATH:/home/dev/python-files

References:

According to the the Python documentation on PYTHONPATH

Augment the default search path for module files. [...]

The default search path is installation dependent, but generally begins with prefix/lib/pythonversion (see PYTHONHOME above). It is always appended to PYTHONPATH.

meaning that some values exist in PYTHONPATH and the default search path is also only appended.

Additionally, this blog post (Archive.org link) also explains clearly why you need to append to PYTHONPATH and not overwrite it. Scrolling down to the section - Special cases and examining the search path explains it clearly (unfortunately no relative URL to that link so you'll have to scroll). Although the user gives the examples on a mac they are very much relevant to any platform

For Windows 10/8/7:

1. Open System Properties (Right click Computer in the start menu, or use the keyboard shortcut Win+Pause)
2. Click Advanced system settings in the sidebar.
3. Click Environment Variables...
4. Select PATH in the System variables section
5. Click Edit

6. Add Python's path to the end of the list (the paths are separated by semicolons). For example:

   C:\Windows;C:\Windows\System32;C:\Python27
   

For Windows XP:

1. Open System Properties (Type it in the start menu, or use the keyboard shortcut Win+Pause)
2. Switch to the Advanced tab
3. Click Environment Variables...
4. Select PATH in the System variables section
5. Click Edit

6. Add Python's path to the end of the list (the paths are separated by semicolons). For example:

   C:\Windows;C:\Windows\System32;C:\Python27
   

7. Test on a new terminal window or if using an integrated terminal within a text editor, close and restart your editor or the changes won't be applied.