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Why do I have to use "py" to execute python commands instead of "python"?

I am a newbie in Python and had a problem with installing Python packages on my windows computer.
I installed Python itself and then had to install the packages "Numpy" and "Matplotlib" as well. My teacher told us to do it with the commands:
python -m pip install --upgrade pip
pip install numpy
pip install matplotlib
I managed to install Python but when I run the first command to install pip I got the error message telling me that Python is not found. I found the command py -m pip --version here and it worked. After running it pip got installed and I got the message "pip 22.3 from C:\Users\Kaja\Programs\Python\Python310\lib\site-packages\pip (python 3.10)". I guessed this message means that its working.
I had a similar problem with the commands to install Numpy and Matplotlib. It only worked with this commands
py -m pip install numpy
py -m pip install matplotlib
I searched the internet and found this question telling me to run the command doskey py=python and it did not work. But when I swapped py and python so that the command was doskey python=py I eventually could run my teachers commands.
I checked the windows documentation and they are using the same commands as my teacher. I am very curious to know why I had this problem because on my fellow students computers it worked without the doskey command.
Edit:
Thank you very much #RustyPython.
I checked my environment variables and the path to the python.exe was already there.
Out of curiousity I deleted the python.exe from the path variable and although I did that the commands still worked! Another thing I tried was to remove the doskey macro like discribed in this article but still the commands still run without any errors.
I think its something else.

When you install python on windows it usually comes with the python launcher. This provides a way to easily access all the python versions installed on your computer.
The python launcher uses the py command which access the default python version.
py -0p will show you all the installed versions.
See https://www.infoworld.com/article/3617292/how-to-use-pythons-py-launcher-for-windows.html for more details.
For the python command to work then the relevant directory containing python.exe needs to be added to your user PATH variable.
As has been said looks the the python directory is not on your PATH, but the python launcher is and finds the installed python.exe.
If you want python to work on command line then you'll need to add it to your PATH variable. https://realpython.com/add-python-to-path/#how-to-add-python-to-path-on-windows

Using VSCode on Mac, can't get Python 3.8 to run, only Python 2.7.16

I just downloaded VSCode on my Mac as well as Python and pip. I downloaded the latest version of Python via VS Microsoft extensions and installed pip using Python -m ensurepip --upgrade. I have python 2.7.16 on my Mac as well, I believe from my OS (it's not something I downloaded). I am trying to use pip and Python in VSCode. I have my interpreter in my virtual environment set to Python 3.8.2, and I created the virtual environment using "python3 -m venv .venv". However, every time I check the python version (with Python --version) in the terminal, it returns Python 2.7.16. I check the pip version, and there is no command found. When I check the pip3 version, I get back the following warning:
WARNING: pip is being invoked by an old script wrapper. This will fail in a future version of pip.
Please see https://github.com/pypa/pip/issues/5599 for advice on fixing the underlying issue.
You can invoke Python with '-m pip' instead of running pip directly to avoid this problem.
pip 21.3.1 from /Users/username/Library/Python/3.8/lib/python/site-packages/pip (python 3.8)
Whenever I run Python -m pip or Python -m pip3, it returns "no module named pip".
When installing Python, I got a warning that Python 3 was not on the PATH, but it did not fix the issue when I tried to add the path. Unfortunately, I don't have much experience adding a path so I may have done that incorrectly.
Finally, I installed streamlit via pip3. It resulted in the following message but seemed to install. However, it could not be resolved when I tried to import streamlit in my code.
WARNING: pip is being invoked by an old script wrapper. This will fail in a future version of pip.
Please see https://github.com/pypa/pip/issues/5599 for advice on fixing the underlying issue.
You can invoke Python with '-m pip' instead of running pip directly to avoid this problem.
Defaulting to user installation because normal site packages is not writeable
How do I add Python 3 to my PATH and ensure that VSCode runs Python 3 instead of 2?

Simply always refer 'python3' rather than 'python'.
python3 --version
python3 -m pip install blahblahblah

Python - package not found although it is installed

I have the following version of python
import sys
print(sys.version)
3.6.5 | packaged by conda-forge | (default, Apr 6 2018, 13:44:09)
[GCC 4.2.1 Compatible Apple LLVM 6.1.0 (clang-602.0.53)]
I installed a package with the following command
pip install wfdb
It is succesfully installed because when I then write the command:
pip show wfdb
The following information appears
Location:
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages
However, when I type the command import wfdb in Python notebook or the version of python in terminal, I get the following message
No module named 'wfdb'
Does it have to do with the path on which python is checking where the packages are? How to check this and how to change it?

You have (at least) 2 Python installations, one managed by Anaconda, the other what appears to be an official Python.org Mac build installed system-wide. The pip command on the command-line is the one tied to the Python.org Mac build.
pip is a script that is tied to a specific Python installation, and there can be multiple versions of the script installed in different locations, and is usually also installed with pipX and pipX.Y to match the X.Y version indicator of the Python version it is tied to. For Python 3.6, that means the same script would also be available as pip3 and pip3.6. (This also means that pip can be connected to Python 2 or Python 3, depending on your exact OS setup. It is not a given that pip, without a version number, installs into Python 2.x as some answers may claim).
Note that when you run a command without a path in your shell, (such as pip as opposed to /usr/bin/pip), you are asking your shell to find the command for you in a number of locations, listed in the PATH environment variable. The first location in the PATH list with that command is then fixed. which -a <command> would tell you all possible PATH-registered locations that the command can be found in. You can always use the full path to a command to bypass the PATH search path.
You can always verify what Python version the pip command is connected to with:
pip -V
which will output the version of pip and the location it is installed with. It'll print something like
pip pipX.pipY path/to/pythonX.Y/site-packages/pip (python X.Y)
where pipX.pipY is the pip version number and path/to/pythonX.Y tells you what Python installation this is for.
You can try to match this with the Python version by running
python -m site
which outputs the Python module search path for that Python version. Python can be run with python, pythonX and pythonX.Y too, and is subject to the same PATH search.
Note the -m switch there, that instructs Python to find a module in it's module search path and execute it as a script. Loads of modules support being run that way, including pip. This is important as that helps avoid having to search for a better pip command if you already can start the right Python version.
You have several good options here:
Since you are using Anaconda, you could look for a conda package for the same project. There is such a package for wfdb. Install it with
conda install wfdb
Anaconda aims to give you a wider software management experience that includes a broader set of software options than just the Python PyPI ecosystem, and conda packages usually manage more things than just the Python package.
Conda packages are usually maintained by a different set of developers from the package itself, so there may be a newer version available on PyPI (requiring pip install) than there is on Conda.
This is not an option for all Python packages, if there is no conda package you have to use pip. See Installing non-conda packages.
you can use the conda command to create a conda environment. Once you have an environment created, you can activate it with
source activate <name_of_cenv>
to alter your PATH settings. With the envirnoment 'active' the first directory listed on your PATH is the one for the conda environment and the pip command will be the one tied to that environment.
Note that a conda environment gives you an isolated environment for a specific project, keeping the library installation separate from the rest of your Python packages in the central site-packages location. If you want to install a package for all of your Anaconda Python projects, don't use a conda environment.
Use the Anaconda Python binary to run pip as a module; when you can run /path/to/python or pythoncommand to open the right Python version, you can use that same path to run /path/to/python -m pip ... instead of pip ... to be absolutely certain you are installing into the correct Python version.
Look for a better pip command, with which -a pip or which -a pip3.6, etc. But if you already know the Python binary, look in the same bin location for pip. If you have anaconda/bin/python, then there probably is a anaconda/bin/pip too.

As you can read here:
pip3 and pip would make a difference only when you are not using any
environment managers like virualenv (or) conda. Now as you are
creating a conda environment which has python==3.x, pip would be
equivalent to pip3.
For this reason it could be you did not activate your Conda environment before installing required packages and running your code.
Activate the new environment:
On Windows:
activate myenv
On macOS (this should be your option) and Linux:
source activate myenv
NOTE: Replace myenv with the name of the environment.

which python
gives the you the PATH to python
and then /path/to/python -m pip install thepackagetobeinstalled
Many thanks #MartijnPieters

You have installed python2.x package and you're using python3.x. Try:
pip3 install wfdb
If you don't have pip3 run:
[apt-get/yum] install python3-pip
You can see what packages you have currently installed by running:
pip freeze
and for python 3.x packages
pip3 freeze
Please remember each time you install a Python package, it will be placed in the directory for one particular Python version. Hence your error.

Fatal Error Using Pip

I have using Python 3.4 in my machine . I have installed the same machine Python 2.7 and do what necessary in Environment Path . In Python34 folder I have changed python.exe to python3.exe . I can use Python2.7 using python command and Python3.4 using python3 command.But there was an error usin pip :
Fatal error in launcher: Unable to create process using '"C:\Python3.4\python.exe" "C:\Python3.4\Scripts\pip.exe" install'
As you see pip still using python.exe . How can I solve this ?

I'll try to be as clear as I can here, the answer you've linked to in the comments above is specifically asking about being able to run multiple versions of python on the same machine, and being able to specify which version is used to run a script from the command line.
when python 3 is installed two executables are added to c:\Windows\ called py.exe and pyw.exe these are used by default when a python script is invoked by double clicking on it in explorer.
if no other command line arguments are set then these executables look inside the script for the shebang line which looks like #!python2 or #!python3.3 and direct the py (or pyw) executable to use that version of python to run the script, note that this could just be #!python which would use the first version found on the system (oldest first) also note that only 2 significant digits can be used (so you couldn't use #!python3.3.4). If no shebang line is found, the first version of python found will be used.
to use a specific version of python from the command line you would then have a couple of options, firstly you could specify the entire path to the python version you want, e.g. C:\Python33\python.exe scriptname.py or you can use flags.
To use a flag you would call py -3.3 scriptname.py which would call the python 3.3 interpreter and pass it the script as an argument for you.
this prevents you needing to mess about with executable names, by messing with the executable names you are breaking your own pip installation. in short there is no reason you should ever need to rename them.

I have the same error when I install python2.7 and python3.6 in my Window7.
After I rename my python.exe, there was an error using pip.
If your pip is the last version,you have to reinstall your pip use the command python3 -m pip install --upgrade --force-reinstall pip.
If your pip is not the last verison ,you can just upgrade your pip with the command python3 -m pip install --upgrade pip.
NOTE. When you install pip for your python2, you hava to change the command as python2 -m pip install --upgrade --force-reinstall pip.
Hope it works for you~

python pip install not working on windows

I have python 2.7.10 installed on windows and I am trying to install Django on the commandline with the following command:
C:/users/user/myproject> python pip install django
This displays the following error:
python: can't open file 'pip' [Errno 2] No such file or directory
Python is installed in C:\Python27 and the PATH environment variable is also set to that.
Why is pip not working?

Since Python 2.7.9 pip is included when python is installed.
However the scripts subfolder of your python installation might not be added to your PATH environment variable, and hence inaccessible by just typing pip install. However as long as your python executable is on the path, you can use the python -m flag to execute the pip module as a script:
python -m pip install SomePackage
This should work from the command line as long as python is on PATH.
If you would like to use pip directly from the cmd.exe prompt you need to add the scripts directory to your PATH environment variable:
SET PATH=%PATH%;C:\Python27\scripts

Some times in windows it especially needs Microsoft visual c++ compiler. If such error persists you can verify the log file and If needed you can download here
http://aka.ms/vcpython27