Develop Reference

How do I run my newly created hello_world.py file from a command prompt window?

I have my first ever hello_world.py file saved in documents\python_work. It runs fine in the Sublime text editor but when I try to navigate to it through a command prompt window, it can't seem to find it. I open a command prompt and type cd documents and it works. I type dir and it shows me the files, but when I type cd python_work (which is the folder my file is in) I get:
The system cannot find the path specified.
The textbook had me add C:\Python and C:\Python\Scripts to the PATH environment variables (not too sure why, just following directions), so perhaps I made a mistake during this process?

If you are the the same folder as the file, type python(or py, depending on your python version) python file.py to run it.
A quick way to get to the folder is find it in the file explorer, and where it shows the file path, click there and type 'cmd' and hit enter. It will open up the Command Prompt from that folder so you don't have to manually navigate to it.

You can go to the File Explorer, right-click on your hello_world.py file and then:
Properties > Details > File Path
and then proceed to copy that path in your cmd.

Is it possible to handle the Environmental Variables within the Batch Script?

I created a very simple batch file as a launcher for a python script, however it does not work fine depending on the "PATH" setup for the user (Python 2 x Python 3).
Since changing the PATH can bring issues with other Python 2 based applications , could I make any update in the .bat to make a temporary change in the PATH while the Py script is running?
The idea is to use the batch to have the minimum interference from the user in the system setup (preferable a double click only).
In case of yes, what could I do?
#echo off
title ###Beta Script Launcher###
python myscript.py
pause

To make a temporary change to the path variable:
path c:\mydir;%path%
the documentation
c:\srv> path /?
Displays or sets a search path for executable files.
PATH [[drive:]path[;...][;%PATH%]
PATH ;
Type PATH ; to clear all search-path settings and direct cmd.exe to search
only in the current directory.
Type PATH without parameters to display the current path.
Including %PATH% in the new path setting causes the old path to be
appended to the new setting.
the normal way to do this for python, however, is to create a virtualenv (https://pypi.org/project/virtualenvwrapper-win/)
mkvirtualenv myenv
.. install everything in this environment ..
and then use it in your start script
#echo off
title ###Beta Script Launcher###
call workon myenv
python myscript.py
pause
(disclaimer, I'm one of the maintainers of virtualenvwrapper-win)

Yes you can edit the environment variables in batch script by using the following command
setx path "%PATH%;C:\New Folder"
based on wherever your python that you want to use is installed.
But this will change the path permanently

How to use Anaconda Python to execute a .py file?

I just downloaded and installed Anaconda on my Windows computer. However, I am having trouble executing .py files using the command prompt. How can I get my computer to understand that the python.exe application is in the Anaconda folder so it can execute my .py files?

You should use Anaconda Prompt instead of common Windows command prompt.
Then navigate to your folder with the .py file and run:
python myfile.py
However if you want to use normal command prompt you should put the path with you're python.exe which is usually in
C:\Users\<username>\AppData\Local\Continuum\anaconda3\python.exe
behind this one put your .py file.

Launch JupyterLab from Anaconda
(Perform the following operation with JupyterLab ...)
Click on icon folder in side menu
Start up "Text File"
Rename untitle.txt to untitle.py (The name of the file started up was also changed)
Start up the "terminal" (In windows the power shell starts up)
Execute the command python untitle.py

Right click on a .py file and choose 'open with'
Scroll down through the list of applications and click something like 'use a different program'
Naviage to C:\Users\<username>\AppData\Local\Continuum\anaconda3
click on python.exe and then click on 'ok' or 'open'
Now when you double click on any .py file it will run it through Anaconda's interpreter and therefore run the python code.
I presume if you run it through the command line the same would apply but perhaps someone could correct me?

Just get to the home of jupyter notebook and select "New" then select "Text file".
Then save the text file as file_name.py
Write your code in the file and save the file.
Then open the "Anaconda Prompt" and then type as follows to run your file
python file_name.py

You can do it from the "Anaconda Prompt"
conda run "my_script.py"

I was doing exactly as Martin Bosch suggested, and was getting the following:
(base) C:\>python command.py
python: can't open file 'command.py': [Errno 2] No such file or directory
I solved it this way:
navigate to the exact file location using the "cd" command
for me this was:
(base) C:\>cd my_scripts
this should put you specifically in the file where your .py script is located.
now you should try to input the name of your file.
(base) C:\my_scripts> test_script.py
you may get asked which program to run this with, and simply find python.exe
After doing this process once, I can simply type (in anaconda prompt)
test_script.py
and it runs no problem, even from the top of the file tree (I don't have to be in the exact file, nor do I have to explicitly give the whole file path)

Anaconda should add itself to the PATH variable so you can start any .py file with "python yourpythonfile.py" and it should work from any folder.
Alternatively download pycharm community edition, open your python file there and run it. Make sure to have python.exe added as interpreter in the settings.

If you get the following error:
can't open file 'command.py': [Errno 2] No such file or directory
Then follow this steps to fix it:
Check that you are in the correct directory where the Python file is.
If you are not in the correct directory, then change the current working directory with cd path. For instance: cd F:\COURSE\Files.
Now that you are in the directory where your .py file is, run it with the command python app.py.

Check where is the directory for the ananconda environment directory which is generally
"C:\Users\[UserName]\.conda\envs\[conda environment directory]"
You will see python.exe in that directory.
After that, you need to use the following command to execute your python file (i.e. xx.py) when you are running Anaconda prompt and you will be done:
"C:\Users\[UserName]\.conda\envs\[conda environment directory]\python.exe" xxx.py
BTW, if you have global variable (i.g. variable yyy) that contain directory, you have to define the global variable that contains full path of directory just below the header (the import section) to prevent the "name 'yyy' is not defined" error to occur:
from pathlib import Path # dealing with path issue
yyy = Path("[DriverLettter]:\Full\Path\of\Directory")

How do I run my Python script? Why does the command line tell me "no such file or directory"?

I have Python 2.7 installed at C:\Python27 and I have added the path C:\Python27\; to the environment variables and .py: to PATHEXT. I am able to launch Python.
I downloaded a folder google-python-exercises to my desktop, which contains a script hello.py.
Following the advice in the Google Developers course, I try to run the script by using python hello.py at the command prompt.
When I attempt this, I get the message: python: can't open file 'hello.py: [Errno 2] No such file or directory. What is wrong, and how am I supposed to fix it? I found that I can solve the problem by running cmd from the folder, but this seems like a temporary solution.

Python cannot access the files in the subdirectory unless a path to it provided. You can access files in any directory by providing the path. python C:\Python27\Projects\hello.py

I resolved this problem by navigating to C:\Python27\Scripts folder and then run file.py file instead of C:\Python27 folder

Options include:
Run the command from the folder where hello.py is located (this way, hello.py is already a relative path to the file). This is the solution that OP found.
Give a proper path to the hello.py file - either absolute (e.g. C:/Users/me/Desktop/google-python-exercises/hello.py) or relative (for example, google-python-exercises/hello.py, if the current working directory is the desktop).
Add a path to the folder (C:/Users/me/Desktop/google-python-exercises) to the PYTHONPATH environment variable, and run the code as a module (python -m hello).
In all cases, a path is being given directly - Python will not "search" for the file.

From your question, you are running python2.7 and Cygwin.
Python should be installed for windows, which from your question it seems it is. If "which python" prints out /usr/bin/python , then from the bash prompt you are running the cygwin version.
Set the Python Environmental variables appropriately
, for instance in my case:
PY_HOME=C:\opt\Python27
PYTHONPATH=C:\opt\Python27;c:\opt\Python27\Lib
In that case run cygwin setup and uninstall everything python.
After that run "which pydoc", if it shows
/usr/bin/pydoc
Replace /usr/bin/pydoc
with
#! /bin/bash
/cygdrive/c/WINDOWS/system32/cmd /c %PYTHONHOME%\Scripts\\pydoc.bat
Then add this to $PY_HOME/Scripts/pydoc.bat
rem wrapper for pydoc on Win32
#python c:\opt\Python27\Lib\pydoc.py %*
Now when you type in the cygwin bash prompt you should see:
$ pydoc
pydoc - the Python documentation tool
pydoc.py <name> ...
Show text documentation on something. <name>
may be the name of a Python keyword, topic,
function, module, or package, or a dotted
reference to a class or function within a
module or module in a package.
...

Try uninstalling Python and then install it again, but this time make sure that the option Add Python to Path is marked as checked during the installation process.

How to run a Python project?

I have installed the Enthought Python distribution on my computer, but I don't have any idea how to use it. I have PyLab and IDLE but I want to run .py files by typing the following command:
python fileName.py
I don't know where to write this command: IDLE, PyLab or Python.exe or Windows command prompt. When I do this in IDLE it says:
SyntaxError: invalid syntax
Please help me to figure this out.

Open a command prompt: Press ⊞ Win and R at the same time, then type in cmd and press ↵ Enter
Navigate to the folder where you have the ".py" file (use cd .. to go one folder back or cd folderName to enter folderName)
Then type in python filename.py

Indeed, the command to run a Python file should be run in the command prompt. Python should be in your path variable for it to work flexible.
When the python folder is added to path you can call python everywhere in the command prompt, otherwise just in your python install folder.
The following is from the python website:
Windows has a built-in dialog for changing environment variables
(following guide applies to XP classical view): Right-click the icon
for your machine (usually located on your Desktop and called “My
Computer”) and choose Properties there. Then, open the Advanced tab
and click the Environment Variables button.
In short, your path is:
My Computer ‣ Properties ‣ Advanced ‣ Environment Variables In this
dialog, you can add or modify User and System variables. To change
System variables, you need non-restricted access to your machine (i.e.
Administrator rights).
Another way of adding variables to your environment is using the set
command in a command prompt:
set PYTHONPATH=%PYTHONPATH%;C:\My_python_lib
If you do it via My Computer, then look for the line named path in Enviroment Variables. Give that the value of your Python installation folder.

Set PYTHON variable to point to the full path of python.exe.
Then type in command prompt console window:
C:\path_to_folder\ python filename.py