pip - 我应该使用 pip 或 pip3 在虚拟环境中安装 python3 软件包吗？

Question

我的 Linux 机器上有 python 2(默认)和 3。我创建了一个虚拟环境来尝试使用 python3 来尝试 pandas。所以，我跑了:

virtualenv -p python3 pandas_env

如果我在此环境中输入 python ，它将进入标准 python shell，默认版本为 python 3

(panda_env)$ python
Python 3.4.3 (default, Sep 14 2016, 12:36:27) 
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> 

为了安装 ipython，我做了:

(panda_env)$ pip install ipython

现在，运行 ipython，它默认为 python2 而不是 3

(panda_env)$ ipython
WARNING: Attempting to work in a virtualenv. If you encounter problems, please install IPython inside the virtualenv.
Python 2.7.6 (default, Jun 22 2015, 17:58:13) 
Type "copyright", "credits" or "license" for more information.

IPython 2.3.1 -- An enhanced Interactive Python.
?         -> Introduction and overview of IPython's features.
%quickref -> Quick reference.
help      -> Python's own help system.
object?   -> Details about 'object', use 'object??' for extra details.

有一个警告说要在virtualenv中安装ipython。我以为环境中确实安装了ipython，为什么默认使用python2.x？

如何在 virtualenv 中正确安装 ipython，以及如何使 ipython 使用 3.x 而不是 2.x？

此外，我应该使用 pip 或 pip3 在 vi​​rtualenv 内安装软件包吗？

Answer 1

注意，对于 python > 3.3，建议您使用 pyvenv 启动虚拟环境命令。从 python > 3.6 开始，此功能已被弃用，取而代之的是 python3 -m venv <environment name> (来自https://docs.python.org/3/library/venv.html)

在回答您的问题时，我认为根据此检查这并不重要:

# start enviroment
$ python3 -m venv test_env; source test_env/bin/activate

# check python version 
(test_env) $ python --version
Python 3.6.0

# check pip and pip3
(test_env) $ which pip
~/Documents/test_env/bin/pip
(test_env) $ which pip3
~/Documents/test_env/bin/pip3

# The pip commands are different, but if we check their versions they are the same and both appear to be using python3.
(test_env) $ pip -V
pip 9.0.1 from ~/test_env/lib/python3.6/site-packages (python 3.6)
(test_env) $ pip3 -V
pip 9.0.1 from ~/test_env/lib/python3.6/site-packages (python 3.6)

# In fact the binaries for pip and pip3 within the environment are identical as you can see with this.
(test_env) $ diff ~/Documents/test_env/bin/pip ~/Documents/test_env/bin/pip3

# Checking with ipython
(test_env) $ pip install ipython
(test_env) $ ipython 
Python 3.6.0 (default, Dec 24 2016, 08:01:42)
Type "copyright", "credits" or "license" for more information.

IPython 5.1.0 -- An enhanced Interactive Python.