尝试为 Flask 创建虚拟 Venv 时出现致命错误？

Question

I am trying to learn FLASK. I am just following this tutorial . I have already created a venv for kivy, and all went right. But now I am learning flask and in CMD, when I pass:

pip install virtualenv

it outputs:

Requirement already satisfied: virtualenv in c:\users\new\appdata\local\programs\python\python39-32\lib\site-packages (20.3.0)
Requirement already satisfied: appdirs<2,>=1.4.3 in c:\users\new\appdata\roaming\python\python39\site-packages (from virtualenv) (1.4.4)
Requirement already satisfied: six<2,>=1.9.0 in c:\users\new\appdata\roaming\python\python39\site-packages (from virtualenv) (1.15.0)
Requirement already satisfied: filelock<4,>=3.0.0 in c:\users\new\appdata\roaming\python\python39\site-packages (from virtualenv) (3.0.12)
Requirement already satisfied: distlib<1,>=0.3.1 in c:\users\new\appdata\roaming\python\python39\site-packages (from virtualenv) (0.3.1)

Then I used:

mkdir newproj
cd newproj

At last:

virtualenv venv

And it said:

Fatal error in launcher: Unable to create process using '"c:\program files\python39-32\python.exe" 
"C:\Program Files\Python39-32\Scripts\virtualenv.exe" ': The system cannot find the file specified.

I tried adding "C:\Program Files\Python39-32\Scripts\virtualenv.exe" to path. But it did not work. How do I fix this?

Answer 1

as of python 3.3 , python is shipped with its built-in virtual environment module venv , it's the official, the standard, the recommended and the difacto module.

refer to: https://docs.python.org/3/library/venv.html#module-venv

so you don't even need to install any 3rd module like virtualenv , pipenv .. to create and manage your virtual environments.

1. create the root folder for your project

C:\> mkdir newproj
C:\> cd newproj

2. create the virtual environment, (as good practice and as seen in many well-known projects on github.. named it venv )

C:\newproj> py -m venv venv

3. activate it

C:\newproj> venv\Scripts\activate

(venv) C:\newproj> pip list
(venv) C:\newproj> pip install flask flask-login ..

4. to deactivate it

(venv) C:\newproj> deactivate
C:\newproj> 

Answer 2

Try to use:

python3 -m virtualenv venv