I have installed the latest Python for Win10 from Releases for Windows. Just typing py in the Command Prompt Window starts Python.

Microsoft Windows [Version 10.0.15048]
(c) 2017 Microsoft Corporation. All rights reserved.

C:\Users\sg7>py
Python 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>`enter code here`

Testing:

>>> print("hello!")
hello!
>>>

Please be aware that in my case Python was installed in C:\Users\sg7\AppData\Local\Programs\Python\Python36> directory

C:\Users\sg7\AppData\Local\Programs\Python\Python36>dir
 Volume in drive C is Windows7_OS
 Volume Serial Number is 1226-12D1

 Directory of C:\Users\sg7\AppData\Local\Programs\Python\Python36

08/05/2018  07:38 AM    <DIR>          .
08/05/2018  07:38 AM    <DIR>          ..
12/18/2017  09:12 AM    <DIR>          DLLs
12/18/2017  09:12 AM    <DIR>          Doc
12/18/2017  09:12 AM    <DIR>          include
12/18/2017  09:12 AM    <DIR>          Lib
12/18/2017  09:12 AM    <DIR>          libs
10/03/2017  07:17 PM            30,334 LICENSE.txt
10/03/2017  07:17 PM           362,094 NEWS.txt
10/03/2017  07:15 PM           100,504 python.exe
10/03/2017  07:12 PM            58,520 python3.dll
10/03/2017  07:12 PM         3,610,776 python36.dll
10/03/2017  07:15 PM            98,968 pythonw.exe
08/05/2018  07:38 AM           196,096 Removescons.exe
08/05/2018  07:38 AM            26,563 scons-wininst.log
08/05/2018  07:38 AM    <DIR>          Scripts
12/18/2017  09:12 AM    <DIR>          tcl
12/18/2017  09:12 AM    <DIR>          Tools
06/09/2016  11:53 PM            87,888 vcruntime140.dll
               9 File(s)      4,571,743 bytes
              10 Dir(s)  20,228,898,816 bytes free

When I am at C:\Users\sg7> directory level python can be invoked by typing AppData\Local\Programs\Python\Python36\python

C:\Users\samg>AppData\Local\Programs\Python\Python36\python
Python 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

Newer Python 3.7 will be installed at: C:\Users\YourUserNameHere\AppData\Local\Programs\Python\Python37

If you wish you can add to your path environment variable: %USERPROFILE%\AppData\Local\Programs\Python\Python36

If you have installed Python 3.7 or above try using keyword "py" instead of "python" on cmd. It worked for me.(I have python 3.7 32bit installed in windows 10 operating system)

One can run the python installer again and click Modify button.

Select py launcher checkbox.

Then click install button and wait for the installation completes.

After all of these, py command will come back to the terminal.

py is itself located in C:\Windows (which is always part of the PATH), which is why you find it. When you installed Python, you didn't check the box to add it to your PATH, which is why it isn't there. In general, it's best to use the Windows Python Launcher, py.exe anyway, so this is no big deal. Just use py for launching consistently, and stuff will just work. Similarly, if py.exe was associated with the .py extension at installation time, a standard shebang line (details in PEP linked above) will let you run the script without even typing py.

I don't know precisely what VSCode uses to find Python (using py.exe directly, using a copy of Python that ships with the editor, performing registry lookup, a config file that just says where to find it, etc.), but that's not really relevant to running your scripts yourself.

I have exact same issue, which started a few days ago, I can recall it was from a windows update.

I feel the problem is the system doesn't really search for the associated run file which is "c:\Python27\python.exe" for me. On an old windows7 machine, I did a test "associate .py to python.exe, and then rename python.exe to some else, and type *.py at command line", a pop-up window asking right executable file shows up; but on windows 10 command prompt, it simply do nothing.

I also tried to run python script in powershell, but it says "Program 'test.py' failed to run: No process is associated with this object"

BTW, on window 10 command line, if run "ftype Python.file", it shows (Python.file="C:\Python27\python.exe" "%1" %*)

I had the same problem, due to a stupid decision from Microsoft.

I had another line in my system path variable: C:\Users\MyUserName\AppData\Local\Microsoft\WindowsApps

And Windows 10 put a python.exe file there that only redirected me to the Python page of the Microsoft Store:

Since this line was above my true Python path, typing python in the cmd prompt opened the Microsoft Store...

Solution:

Type App execution aliases in the Windows 10 search bar, and then uncheck the aliases for python.exe and python3.exe. More information is here.

Whenever I run python in cmd I get this error 'python' is not recognized as an internal or external command, operable program or batch file.

You need to add python.exe to your Windows path variable(s). You can do this when installing Python with the official installer from python.org by selecting a custom installation and marking the correct option to add Python to your environment variables.

If you need to add the path to Python to your Windows path variable(s) manually (ex. because Python is already installed), look for the Windows Search and type env into it. Click the first link indicating you wish to edit your environment variables.

• If you are on Windows 7, add e.g. ;C:\path\to\python to the end of your Path variable under System variables, where python is your Python installation folder (only use PATH under your user variables if you want Python to be accessible by that user alone). If you click the wrong link in Windows Search, you may need to click the Environment Variables... button to get to the settings described.

• On Windows 10, just add C:\path\to\python to the end of the list (in a new field).

• Do not add python.exe to your path entry (i.e. C:\path\to\python\python.exe is wrong).

Python will work in my Jupyter Notebook, but if I need to pip install something I am unable to do so.

Adding Python to you environment variables through the official installer (above) should solve this. If not, you will need to perform the same (rough) steps above but add C:\path\to\python\Scripts to your path (Scripts is the folder where pip.exe lives).

In either case, reboot your PC before attempting to access python/pip from the command line.

You need to add the python executable path to your Window's PATH variable.

1. From the desktop, right-click My Computer and click Properties.
2. In the System Properties window, click on the Advanced tab.
3. In the Advanced section, click the Environment Variables button.
4. Highlight the Path variable in the Systems Variable section and click the Edit button.
5. Add the path of your python executable(c:\Python27\). Each different directory is separated with a semicolon. (Note: do not put spaces between elements in the PATH. Your addition to the PATH should read ;c:\Python27 NOT ; C\Python27)
6. Apply the changes. You might need to restart your system, though simply restarting cmd.exe should be sufficient.
7. Launch cmd and try again. It should work.