Python off a Flash Drive, how to start IDLE?

Question

I was trying to run Python 3.3 off of my flash drive. I already tried Portable Python, but most of what it had wouldn't open, and it crashed my laptop.

So, I deleted it, and installed regular Python. Then, I wanted to start adding my favorite modules. And, I needed a way to start IDLE without the original shortcut.

To install modules, I added my Python install to my PATH variable.

To make all this easier, I made a batch file, using some code I found on this question.

So far, I have this. It also asks for the drive letter, because that changes from computer to computer.

@echo off
echo This only works if your Python install is added to the system-wide PATH variable
set /p Path="Enter the Drive Letter on this computer. No Symbols, Just the Letter, Capital"
cd %Path%:\Program Files\Python33
echo type this when python comes up...
echo import idlelib.PyShell
echo idlelib.PyShell.main()
echo.
echo.
echo.
echo.
python

It outputs this:

If you go on and follow the instructions and type what it says, it brings up IDLE. I couldn't figure out how to get the batch file to actually type into the Python prompt, so I told it to tell the user to type what needed to be typed.

What I need to know is, how can I change the PATH variable from within the batch file. Also, how to I remove it when I'm done (this isn't as important, and could even be in a separate batch file).

Or, alternatively, is there a way just to shortcut to IDLE?

Also, is there a way to run .py files without the command line, with the Python install on my flash drive?

Thanks!

Answer 1

You can invoke Python with this command line:

python -c"import idlelib.PyShell;idlelib.PyShell.main()"

and it will bring-up IDLE shell without the need for the user to type anything.

Edit: BTW, Are you sure you really need to change the global path settings. Try to see if the following script can start Python the way you want. You must put it in the root of the USB drive where you have your Python installation.

@echo off
setlocal
set SCRIPT_DIR=%~dp0
:: Removes trailing backslash (for readability in the following)
set SCRIPT_DIR=%SCRIPT_DIR:~0,-1%
set PYTHON_HOME=%SCRIPT_DIR%\Program Files\Python33
set PATH=%PYTHON_HOME%;%PATH%
"%PYTHON_HOME%\python.exe" -c"import idlelib.PyShell;idlelib.PyShell.main()"

Edit: Every process has an associated environment, which is a set of name-value pairs called environment variables. When a process is started it gets a copy of the environment of its parent process. The global OS settings for environment variables are used for processes started directly from the OS (GUI or command line) shell. The set command in batch files sets or modifies an environment variable in the environment of the current process (not globally).

All the set commands you see in the above script change only the environment of the current process. These changes will be seen by the process created by the last line (python.exe) because it is a child process of the command shell (cmd.exe) process that is executing the batch-file.

The line

set PATH=%PYTHON_HOME%;%PATH%

prepends the content of the PYTHON_HOME variable to the PATH variable of the current process. For example, if PATH were c:\foo\bar;d:\aaa\bbb and PYTHON_HOME were c:\python then the new value of PATH will be c:\python;c:\foo\bar;d:\aaa\bbb