Windows 11 installation
CPython, pip, and IDLE
From python.org you can download the reference implementation of Python, nicknamed CPython (since it is coded in the programming language C). Since Python 3.14 (October 2025), Python should now be installed using the Python install manager.
- Open www.python.org/downloads
- Select “Download Python install manager”
- Run the downloaded application, e.g python-manager-25.2.msix
- Remember to answer YES when asked “Add commands directory to your PATH now?”
Note. By default a 64-bit Windows version of Python is installed. For memory consuming Python programs on Windows (requiring above 2GB of RAM), it is important that you download the 64 bit version of Python, also available at www.python.org/downloads/windows as “Windows installer (64-bit)”. The 32-bit version is “Windows installer (32-bit)”, and limits your programs to using 2GB of RAM.
Additional Python packages are installed using the module “pip”, included in the above download. To e.g. install the SciPy package that will be used in the course (see SciPy.org for more information on the package):
- Open a Command Prompt (Windows-key + type “cmd”)
- Run “python -m pip install scipy”
Part of the download is IDLE, an integrated development environment for Python. Existing Python files (ending on .py) can be opened and edited in IDLE by right-clicking on the file and selecting “Edit with IDLE”. The IDLE application should also appear in your Windows Start menu (or Windows-key + “IDLE”).
A Python program program can be executed in several ways.
- The easiest is just to double click on the file name, but this closes the output window immediately after the program terminates.
- Open the program in IDLE and press F5 to “Run Module”.
- Execute the program from a Windows shell:
- Open a Command Prompt (Windows-key + type “cmd”)
- Change to the relevant folder, e.g. “cd C:\Users\ username \Desktop"
- Run the python program (here test.py on your desktop) using e.g. “python test.py”
Anaconda - an easy start to Python
Anaconda wrote on their webpage that it is “The Most Popular Python Data Science Platform”. Anaconda bundles Python, a lot of libraries, and the Spyder IDE. To install Anaconda:
- Open www.anaconda.com/download
- Select “Download”
- Run the download application, e.g. Anaconda3-2025.12-1-Windows-x86_64.exe
Note: Anaconda does not necessarily support the most recent version of Python provided at python.org.
PyPy - for the performance demanding Python programmer
PyPy is an alternative implementation of the Python language that is often faster than CPython, but does not support the most recent versions of Python. To install PyPy:
- Open pypy.org
- Select “Download PyPy”
- Find the section with the most recent Python 3 implementation and download the Windows binary (64bit) (possibly https://downloads.python.org/pypy/pypy3.11-v7.3.20-win64.zip).
- Unzip the download folder and move the folder to an appropriate place, e.g. C:\Program Files\
- Add the PyPy folder to your path:
- Windows-key + “Edit the system environment variables”
- Select “Environment variables”
- Select “Path”
- Select “New” and add the path to the folder with pypy3.exe, e.g. C:\Program Files\pypy3.11-v7.3.30-win64\
The speed improvements of PyPy over CPython are due to the usage of the Just-In-Time compilation technique, that e.g. also is used inside the Google Chrome browser for executing JavaScript (see the Wikipedia page on Chrome V8 and by Java Virtual Machines for executing Java programs (bytecode) (see more on Just-In-Time compilation on Wikipedia).