Variable Not Set When Same Batch Script Run Twice

Question

I have a batch script that is just toggles my python pathing. When I run it a second time, my variable doesn't get set but the string I want it to be set to is echoed onto the console.

First time running the script:

C:\Users\Hai\Desktop>FOR /F "delims=" %I IN ('Python -V') DO (
setlocal
 set "ver=%I"
)

C:\Users\Hai\Desktop>(
setlocal
 set "ver=Python 3.6.3"
)

Second time running same batch file without closing console:

C:\Users\Hai\Desktop> chPythonVer.bat

C:\Users\Hai\Desktop>FOR /F "delims=" %I IN ('Python -V') DO (
setlocal
 set "ver=%I"
)
Python 2.7.15

This is how I'm setting my variable:

FOR /F "delims=" %%I IN ('Python -V') DO (
    setlocal
    set "ver=%%I"
)

echo the current version pathed is %ver%

SET /P c=would you like to switch to the other version? [y/n] 
IF /I "%c%" EQU "y" (
    IF "%ver%" EQU "Python 3.6.3" (
        endlocal
        set PATH= ...
        echo switched to Python 2.7.15
        pause
    ) ELSE (
        endlocal
        set PATH= ...
        echo switched to Python 3.6.3
        pause
    )   
) ELSE IF /I "%c%" EQU "n" (
    endlocal
    pause
)

You could possibly use Python Launcher for Windows instead to choose Python version. — michael_heath
– michael_heath, Commented May 11, 2018 at 14:36

score 2 · Accepted Answer · 2024-03-02 06:03:45Z

2

Firstly, it is a bad idea to set variable names to existing environment variable names. i.e path

You would also need delayedexpansion as you are setting a variable in a code block. So rename PATH to myPATH:

@echo off
setlocal enabledelayedexpansion
FOR /F "delims=" %%I IN ('Python -V') DO (
    set "ver=%%I"
)

echo the current version pathed is %ver%

SET /P c=would you like to switch to the other version? [y/n] 
IF /I "!c!" EQU "y" (
IF "!ver!" EQU "Python 3.6.3" (
    set mypath= ...
    echo switched to Python 2.7.15
    pause
) ELSE (
    set mypath= ...
    echo switched to Python 3.6.3
    pause
)   
    ) ELSE IF /I "!c!" EQU "n" (
   pause
)

If however you were looking at actually updating the system path temporarily then, ignore the first comment and you should then set path as:

SET PATH=%PATH%;c:\whereever\python is\

edited Mar 2, 2024 at 6:03

answered May 11, 2018 at 5:56

user7818749

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3 Comments

user6811411 Over a year ago

It's not that easy, the python -v presumes it is in the path. If you prepend the other version to the path to override you over time get a very long path - so you have to remove the previous version.

aschipfl Over a year ago

set "PATH=... just updates the PATH variable for the current cmd session, so to permanently change it, take a look at the setx command...

user7818749 Over a year ago

@aschipfl yes, he seems to want it set it locally like that, look at the setlocal/endlocal in his script..

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