Flask是为Python 2.7而非Python 3安装的

Question

I installed Flask following the steps given in this webpage , so first I set the enviroment for Python 3 by following command code:

pooja@X1-Carbon-6:~/Documents/sva/projekten$  python3 -m venv venv
pooja@X1-Carbon-6:~/Documents/sva/projekten$ . venv/bin/activate
(venv) pooja@X1-Carbon-6:~/Documents/sva/projekten$ python
Python 3.5.2 (default, Nov 23 2017, 16:37:01) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 

which so far sounds good, then I tried to install Flask and this is what happens:

(venv) pooja@X1-Carbon-6:~/Documents/sva/projekten$ sudo pip install flask
[sudo] password for pooja: 
The directory '/home/pooja/.cache/pip/http' or its parent directory is not owned by the current user and the cache has been disabled. Please check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
The directory '/home/pooja/.cache/pip' or its parent directory is not owned by the current user and caching wheels has been disabled. check the permissions and owner of that directory. If executing pip with sudo, you may want sudo's -H flag.
Collecting flask
  Downloading https://files.pythonhosted.org/packages/7f/e7/08578774ed4536d3242b14dacb4696386634607af824ea997202cd0edb4b/Flask-1.0.2-py2.py3-none-any.whl (91kB)
    100% |████████████████████████████████| 92kB 836kB/s 
Requirement already satisfied: Jinja2>=2.10 in /usr/local/lib/python2.7/dist-packages (from flask) (2.10)
Requirement already satisfied: itsdangerous>=0.24 in /usr/local/lib/python2.7/dist-packages (from flask) (0.24)
Requirement already satisfied: Werkzeug>=0.14 in /usr/local/lib/python2.7/dist-packages (from flask) (0.14.1)
Requirement already satisfied: click>=5.1 in /usr/local/lib/python2.7/dist-packages (from flask) (7.0)
Requirement already satisfied: MarkupSafe>=0.23 in /usr/local/lib/python2.7/dist-packages (from Jinja2>=2.10->flask) (1.0)
Installing collected packages: flask
Successfully installed flask-1.0.2
(venv) pooja@X1-Carbon-6:~/Documents/sva/projekten$ flask --version
Flask 1.0.2
Python 2.7.12 (default, Dec  4 2017, 14:50:18) 
[GCC 5.4.0 20160609]
(venv) pooja@X1-Carbon-6:~/Documents/sva/projekten$ 

Does anybody have any ideas, how can I install Flask for Python 3 and not for Python 2.7?

Answer 1

You created and activated a virtualenv, and then ignored it , because you used sudo :

$ sudo pip install flask

Activating a virtualenv simply sets the PATH variable to put the commands in the bin directory first when running pip , python , etc.

But when you use sudo , you create a new sub-shell running under the root user, and you then effectively tell the OS to not use the current shell configuration . And the pip command found when executing as the root user is not the same command as the one set up for your virtualenv.

Next, you would not want to install packages as root into your virtualenv anyway. Install them as the current user instead.

Simply drop the sudo :

$ pip install flask

or even directly reference the bin/pip command:

$ bin/pip install flask

The whole point of a virtualenv is to give you an isolated Python environment that is your own, where you can add and remove packages as you need to, without needing root access.