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Python安装+python2和python3的版本切换设置

MacOS Python 集合

Posted by Yuankun Li on 2020-06-10

安装Python

廖雪峰安装Python

如果你正在使用Mac，系统是OS X>=10.9，那么系统自带的Python版本是2.7。要安装最新的Python，有两个方法：

方法一：从Python官网下载安装程序

从Python官网下载Python 最新的安装程序
从Python官网下载Python 3.11.9 安装程序
从Python官网下载Python 2.7.18 (python2最后一个版本)

下载后双击运行并安装:

安装目录：

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which python3
/Library/Frameworks/Python.framework/Versions/3.11/bin/python3
# python2
which python
/Library/Frameworks/Python.framework/Versions/2.7/bin/python

方法二：Homebrew and Python

如果安装了Homebrew，直接通过命令brew install python3安装即可。
MAC Monterey 系统上新版本Homebrew， 例如 3.3.12，默认路径变为/opt/homebrew/Cellar/python@3.10, 下面的子目录就是用brew安装的其他包。

安装目录：/usr/local/Cellar/python@3.11
可执行文件目录：/usr/local/bin/python3.11

/usr/local/bin和/opt/homebrew/bin都是用于存放可执行文件的目录。它们的区别在于

  • /usr/local/bin：这是Mac OS系统中的一个标准目录，用于存放用户自己安装的软件或第三方软件的可执行文件。当你使用Homebrew或其他包管理器安装软件时，它们通常会将可执行文件安装到/usr/local/bin目录下。这样做的好处是，你可以通过在终端中直接输入命令来运行这些软件。

  • /opt/homebrew/bin：这是Homebrew软件包管理器的默认安装目录。当你使用Homebrew安装软件时，它会将软件的可执行文件安装到/opt/homebrew/bin目录下。这样做的好处是，Homebrew可以管理软件的版本和依赖关系，并确保这些软件在系统中正确地运行。

总的来说，/usr/local/bin是一个通用的可执行文件目录，而/opt/homebrew/bin是Homebrew软件包管理器的特定安装目录。

查找Python路径

根据你实际的python安装路径，进行下一步的Environment path的设置。

Mac 自带python 路径

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which python
/usr/bin/python

从Python官网下载Python 的安装程序安装路径

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which python3
/Library/Frameworks/Python.framework/Versions/3.11/bin/python3
which python
/Library/Frameworks/Python.framework/Versions/2.7/bin/python

Homebrew python 路径

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which python3
/opt/homebrew/bin/python3

where python
/usr/local/bin/python

查看python版本

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python -V

python --version
Python 2.7.18

python3 --version
Python 3.12.5

python2和python3的版本切换设置

按这篇Python笔记：Mac上python2和python3的版本切换的简单处理方式的方法设置：

修改bash_profile

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# 我的.bash_profile没有python配置，都配在了~/.zprofile
vi ~/.bash_profile

如果使用zsh则相应修改~/.zprofile

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vi ~/.zprofile
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# -------------------- Python --------------------
# Setting PATH for Python 2.7 MAC Default
# The original version is saved in .bash_profile.pysave
# export PATH="/usr/bin:${PATH}"

# Setting PATH for Python 2.7
# The original version is saved in .zprofile.pysave
PATH="/Library/Frameworks/Python.framework/Versions/2.7/bin:${PATH}"
export PATH

# Setting PATH for Python 3.11
# The original version is saved in .zprofile.pysave
PATH="/Library/Frameworks/Python.framework/Versions/3.11/bin:${PATH}"
export PATH

# Setting PATH for Python 3.12 Homebrew
# The original version is saved in .bash_profile.pysave
# export PATH="/opt/homebrew/bin:${PATH}"
# If you using Homebrew to install Python 3
# export PATH="/usr/local/bin:${PATH}"

修改bashrc

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vi ~/.bashrc

如果使用zsh则相应修改~/.zshrc

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# 我的~/.zshrc没有python配置，都配在了 ~/.bashrc
vi ~/.zshrc
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# python
alias python2='/usr/bin/python2.7'
# alias python2='/Library/Frameworks/Python.framework/Versions/2.7/bin/python2' # 2.7.18  in work machine
alias python3='/Library/Frameworks/Python.framework/Versions/3.11/bin/python3.11' # 3.11 in work machine

# If you using Homebrew to install Python 3
# alias python3='/usr/local/bin/python3.9'

alias python=python3

使设置生效：

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source ~/.bashrc

设置完后：

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$ python -V
Python 3.8.0
$ which python2
python2: aliased to /usr/bin/python2.7
$ which python3
python3: aliased to /Library/Frameworks/Python.framework/Versions/3.11/bin/python3.9
$ which python
python: aliased to python3

切换Python版本

修改.bashrc文件中的刚添加的最后一行
修改 alias python=python3 或者改为alias python=python2

使设置生效：

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source ~/.bashrc

python包管理工具

pip

pip 是 Python 的官方包管理工具，用于安装和管理 Python 包。它允许用户从 Python Package Index (PyPI) 上安装第三方库，并可以通过简单的命令来更新和卸载已安装的包。

pipenv

pipenv 是一个基于 pip 的虚拟环境管理工具，它可以帮助开发者更方便地管理项目的依赖关系。pipenv 可以自动为每个项目创建一个独立的虚拟环境，并且可以自动跟踪项目所需的包及其版本。它还提供了一些方便的命令，如安装、卸载、更新依赖等。
因此，pipenv 可以看作是 pip 的一个扩展，它在 pip 的基础上提供了更强大的功能和更方便的使用方式，用于更好地管理 Python 项目的依赖关系。

  • Pipenv Crash Course - Youtube
    • Pipenv官方文档
    • Python—pipenv精心整理教程
      • 安装pipenv pip install pipenv注：无法用pip管理的包，pipenv同样无法使用。pipenv依赖：psutil, virtualenv-clone, pew, certifi, urllib3, chardet, requests, mccabe, pyflakes, pycodestyle, flake8等第三方模块。
      • pipenv shell 生成Pipfile文件
      • pipenv install langchain 即可生成Pipfile.lock文件

报错解决

pip not found 和 Pychram配置

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where python3
python3: aliased to /opt/homebrew/Cellar/python@3.13/3.13.5/bin/python3.13 /opt/homebrew/bin/python3 /usr/bin/python3

pip install --user pipenv 
zsh: command not found: pip

# 1. Check which Python you’re actually using
which python3
python3: aliased to /opt/homebrew/Cellar/python@3.13/3.13.5/bin/python3.13 

python3 --version
Python 3.13.5 

# 2. Check if pip is installed for that Python
python3 -m pip --version
pip 25.1.1 from /opt/homebrew/lib/python3.13/site-packages/pip (python 3.13)


python3 -m pip install --user pipenv
error: externally-managed-environment × This environment is externally managed ╰─> To install Python packages system-wide, try brew install xyz, where xyz is the package you are trying to install. If you wish to install a Python library that isn't in Homebrew, use a virtual environment: python3 -m venv path/to/venv source path/to/venv/bin/activate python3 -m pip install xyz If you wish to install a Python application that isn't in Homebrew, it may be easiest to use 'pipx install xyz', which will manage a virtual environment for you. You can install pipx with brew install pipx You may restore the old behavior of pip by passing the '--break-system-packages' flag to pip, or by adding 'break-system-packages = true' to your pip.conf file. The latter will permanently disable this error. If you disable this error, we STRONGLY recommend that you additionally pass the '--user' flag to pip, or set 'user = true' in your pip.conf file. Failure to do this can result in a broken Homebrew installation. Read more about this behavior here: <https://peps.python.org/pep-0668/> note: If you believe this is a mistake, please contact your Python installation or OS distribution provider. You can override this, at the risk of breaking your Python installation or OS, by passing --break-system-packages. hint: See PEP 668 for the detailed specification.

that error comes from PEP 668. Homebrew marks its Python as an “externally managed environment”, so pip install --user pipenv is blocked to prevent breaking your system Python. (Recommended): Use pipx

do it step by step with pipx so you’ll end up with a clean, working pipenv command.

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# 1. Install pipx via Homebrew
brew install pipx

# 2. Make sure pipx’s path is added
pipx ensurepath

#This may tell you to add something like this to your ~/.zshrc:
# export PATH="$HOME/.local/bin:$PATH"
# Then reload your shell:
source ~/.zshrc

# 3. Install pipenv with pipx
pipx install pipenv

# 4. Verify it’s working
which pipenv
/Users/yuanli/.local/bin/pipenv

pipenv --version
pipenv, version 2025.0.4
# After this, pipenv will always be available globally, isolated from Homebrew’s Python environment, 
# and you won’t run into the PEP 668 restrictions anymore.

Once pipenv is installed with pipx, you can hook it into PyCharm so your projects automatically use the right environment. Here’s how:

🔹 Step 1: Make sure pipenv is in PATH

Check in your terminal:
which pipenv

It should point to something like:
/Users/<you>/.local/bin/pipenv

If PyCharm can’t find it later, you may need to add that path to PyCharm’s environment PATH (I’ll show how in Step 4).

🔹 Step 2: Open PyCharm Preferences

macOS: PyCharm > Preferences…

Windows/Linux: File > Settings…

Go to:
Project: > Python Interpreter

🔹 Step 3: Add a new interpreter from Pipenv

Click the ⚙️ gear icon > Add Interpreter.

Choose Pipenv Environment.

In the dialog:

Select Pipenv executable → click … and point to the result of which pipenv.

Choose Pipenv environment:

Existing environment → if you already ran pipenv install in your project.

New environment → PyCharm will run pipenv install for you.

PyCharm will detect the Python version from Pipenv and set up the interpreter.

Look at Python Interpreter

If it’s not the Pipenv venv from Step 1, click the ⚙️ → Add Interpreter → Existing environment

Navigate to:

/Users/yuanli/.local/share/virtualenvs/python-NwH-YMu4/bin/python

Click OK and apply.

🔹 Step 4: (If PyCharm can’t find pipenv)

If PyCharm complains it can’t find pipenv, add its location to the IDE’s PATH:

Go to PyCharm > Preferences > Tools > Terminal.

Add this to the “Shell Path” or “Environment variables” section:

PATH=$HOME/.local/bin:$PATH

Restart PyCharm.

🔹 Step 5: Verify

Once set, open a PyCharm terminal and run:

pipenv --version
python --version

Both should match what you expect from your Pipenv environment.

pip3 install 成功- import requests仍找不到module:ModuleNotFoundError

命令行报错 command cannot found pip 2

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$ pip install wakatime
command cannot found pip

Maybe you have installed both python2 and python3. python3 may have been installed later.

You may try to use pip3 instead of pip.

First, input the command:

pip3 -V
If you see the version, the pip3 can be used.

In case you do

which pip
and it doesn’t show the path, just do

which pip3
This will print the path which is /usr/local/bin/pip3

Then do open ~/.zshrc or nano ~/.bash_profile.

Make alias for pip like:

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alias pip=/usr/local/bin/pip3

N.B: You copy that line above and paste in your .zshrc file.

After do source ~/.zshrc and close .zshrc

本文由Yuankun Li创作和发表,采用BY-NC-SA国际许可协议进行许可,转载请注明作者及出处。
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