batch file to check if Python is installed

I've written a batch script that checks if Python is installed, if it's not installed - it initiates the Python installer contained in the same folder as itself.

I'm using the following code:

reg query "hkcu\software\Python 2.6"

if ERRORLEVEL 1 GOTO NOPYTHON 

:NOPYTHON
ActivePython-2.6.4.8-win32-x86.msi

reg query "hklm\SOFTWARE\ActiveState\ActivePerl\" 1>>Output_%date%_%time%.log 2>&1
if ERRORLEVEL 1 GOTO NOPERL 

reg query "hklm\SOFTWARE\Gtk+"
if ERRORLEVEL 1 GOTO NOPYGTK 


:NOPERL
ActivePerl-5.10.1.1006-MSWin32-x86-291086.msi 1>>Output_%date%_%time%.log 2>&1

:NOPYGTK
pygtk_windows_installer.exe

But in some cases the installer st开发者_运维技巧arts up even if Python is installed. What is the problem here?

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For those who just want a simple check if Python is installed and can be executed without going into the registy, in your batch file:

:: Check for Python Installation
python --version 2>NUL
if errorlevel 1 goto errorNoPython

:: Reaching here means Python is installed.
:: Execute stuff...

:: Once done, exit the batch file -- skips executing the errorNoPython section
goto:eof

:errorNoPython
echo.
echo Error^: Python not installed

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Your code doesn't branch after the registry query is done. No matter what the first if ERRORLEVEL evaluates to, the next step is always to step into the :NOPYTHON label.

Ed: Here is an example how to make it work. The idea is to add another goto statement which will skip the :NOPYTHON label if desired.

reg query "hkcu\software\Python 2.6"  
if ERRORLEVEL 1 GOTO NOPYTHON  
goto :HASPYTHON  
:NOPYTHON  
ActivePython-2.6.4.8-win32-x86.msi  

:HASPYTHON  
reg query "hklm\SOFTWARE\ActiveState\ActivePerl\" 1>>Output_%date%_%time%.log 2>&1  

---

Here's my method.

The python -V command will return the version number and the find command with the aid of the /v switch will search for the omittance of Python and there's also a normal one without that switch.

@echo off & title %~nx0 & color 5F

goto :DOES_PYTHON_EXIST

:DOES_PYTHON_EXIST
python -V | find /v "Python" >NUL 2>NUL && (goto :PYTHON_DOES_NOT_EXIST)
python -V | find "Python"    >NUL 2>NUL && (goto :PYTHON_DOES_EXIST)
goto :EOF

:PYTHON_DOES_NOT_EXIST
echo Python is not installed on your system.
echo Now opeing the download URL.
start "" "https://www.python.org/downloads/windows/"
goto :EOF

:PYTHON_DOES_EXIST
:: This will retrieve Python 3.8.0 for example.
for /f "delims=" %%V in ('python -V') do @set ver=%%V
echo Congrats, %ver% is installed...
goto :EOF