macOS下安装运行python3
macOS 下使用 brew 安装 python3 以及使用简介。
brew 安装 Python3#
brew search python3#
在 macOS 终端输入 brew search python3 即可搜索 Python3 安装包：
faner@FAN-MB0:~|⇒ brew search python3
==> Searching local taps...
python3 ✔
==> Searching taps on GitHub...
brew info python3#
在 macOS 终端输入 brew info python3 即可查询 Python3 安装包信息：
faner@FAN-MB0:~|⇒ brew info python3
python3: stable 3.6.3 (bottled), devel 3.7.0a1, HEAD
Interpreted, interactive, object-oriented programming language
https://www.python.org/
Not installed
brew install python3#
在 macOS 终端输入 brew install python3 即可安装 Python3。
使用 python3#
python3 --version#
执行 python -V（python --version）查看 macOS/Xcode 自带的 python2 的版本号。
安装 python3 后，执行 python3 -V（python3 --version）可查看安装的 python3 的版本号。
faner@FAN-MB0:~|⇒ python -V
Python 2.7.10
faner@FAN-MB0:~|⇒ which python
/usr/bin/python
faner@FAN-MB0:~|⇒ whereis python
/usr/bin/python
faner@FAN-MB0:~|⇒ python3 --version
Python 3.6.3
faner@FAN-MB0:~|⇒ which python3
/usr/local/bin/python3
raspbian 默认已经安装了 python2 和 python3：
pi@raspberrypi:~ $ python --version
Python 2.7.13
pi@raspberrypi:~ $ which python
/usr/bin/python
pi@raspberrypi:~ $ python3 -V
Python 3.5.3
pi@raspberrypi:~ $ which python3
/usr/bin/python3
python3 Orignial#
macOS 通过 brew 安装的 python3 默认在 /usr/local/Cellar/python3/ 目录下，然后软链（symlink）到 /usr/local/bin/ 目录下。
通过 ls -l 命令可显示 python3 的原身：
faner@FAN-MB0:~|⇒ ls -al /usr/local/bin/python3
lrwxr-xr-x 1 faner admin 35 Nov 3 08:09 /usr/local/bin/python3 -> ../Cellar/python3/3.6.3/bin/python3
进一步通过 ls -l 命令查找 python3 的终极原身：
faner@FAN-MB0:~|⇒ ls -al /usr/local/Cellar/python3/3.6.3/bin/python3
lrwxr-xr-x 1 faner admin 55 Nov 3 08:09 /usr/local/Cellar/python3/3.6.3/bin/python3 -> ../Frameworks/Python.framework/Versions/3.6/bin/python3
Hello World from Python3#
新安装的 Python3 与系统自带的旧版 Python2 并存，使用时指明版本号即可。
在安装并配置好环境变量的系统终端中输入 python 默认进入 python2 的命令行编辑交互控制台。若显式指定 python3（或 python3.6），则可启动运行版本 3。
The interpreter's line-editing features include interactive editing, history substitution and code completion on systems that support readline.
The interpreter operates somewhat like the Unix shell: when called with standard input connected to a tty device, it reads and executes commands interactively; when called with a file name argument or with a file as standard input, it reads and executes a script from that file.
python shell 前导符（primary prompt）为3个大于号 >>>（类似 bash shell 的 $），等待输入 python 命令。
在 python(2) 下输入 >>> print "Hello World from Python2"，在 python3 下输入 >>> print("Hello World from Python3") 可打印 Hello World from Python*。
faner@FAN-MB0:~|⇒ python
Python 2.7.10 (default, Feb 7 2017, 00:08:15)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.34)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print "Hello World from Python2"
Hello World from Python2
>>> ^D
faner@FAN-MB0:~|⇒ python3
Python 3.6.3 (default, Nov 3 2017, 08:08:42)
[GCC 4.2.1 Compatible Apple LLVM 9.0.0 (clang-900.0.35)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print "Hello World from Python3"
File "<stdin>", line 1
print "Hello World from Python3"
^
SyntaxError: Missing parentheses in call to 'print'. Did you mean print("Hello World from Python3")?
>>> print ("Hello World from Python3")
Hello World from Python3
>>>
python3 XXX.py 指定 python3 执行 py 脚本文件。
multi line input#
当输入 (,[,{，尚未定义完时，解析器会自动接受续行输入。
>>> str1=('hello'
... 'world')
>>> str1
'helloworld'
>>> list1=[1,3,5,
... 7,9,11]
>>> tuple1=(1,4,9,
... 16,25,36)
>>> set1={2,4,6,
... 8,10,12}
>>> exit(
... )
如果一行输入不下，可以输入反斜杠 \，新起续航书写。
三引号（'''）开头结尾的输入，中间支持换行输入：
以上每行尾部加反斜杠 \ 示意续行，防止分行：
>>> hello = '''Hello \
... World \
... from \
... Python3'''
>>> print(hello)
Hello World from Python3
comment#
python 控制台及脚本中均支持开头或语句尾部以 # 开始的注释。
quit/exit#
按下 <C-d>（windows 下为 <C-z>）或输入 quit()/exit() 即可退出 python shell，退回到系统 shell。
Typing an end-of-file character (
Control-Don Unix,Control-Zon Windows) at the primary prompt causes the interpreter to exit with a zero exit status. If that doesn't work, you can exit the interpreter by typing the following command:quit().
default python3#
如果想输入 python 默认启动 python3，可以在 bash 配置文件中 ~/.bash_profile 或 ~/.bashrc 增加 alias 将 python 指向 Python3：
alias python="/usr/local/Cellar/python3/3.6.3/Frameworks/Python.framework/Versions/3.6/bin/python3.6"
或
废弃 Python 2.7#
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2.x 升级为 3.x#
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compatibility#
pi@raspberrypi:~ $ pip3 show six
Name: six
Version: 1.10.0
Summary: Python 2 and 3 compatibility utilities
Home-page: http://pypi.python.org/pypi/six/
Author: Benjamin Peterson
Author-email: [email protected]
License: MIT
Location: /usr/lib/python3/dist-packages
Requires:
removal#
How to remove python 2.7 from MacBook Pro 14? - Apple Community
Apple Finally Removing Python 2 in macOS 12.3 - MacRumors
Apple removing Python 2.7 on Mac - What does this mean for IT admins?
Back in 2019, Apple announced its plans to deprecate the Python 2.7 scripting language. With the release of macOS Monterey, Apple made good on that promise. macOS devices that are on versions 12.3 and above will no longer be able to execute scripts and operations that run on Python 2.7.
But what about apps and scripts that use the Python 3 runtime? Here too, users may encounter a slight hiccup. At least, during the first run.
Python 3 does not come automatically installed on macOS devices (even on those above versions 12.3). Hence, if the user tries to run a software, app, or script that calls on Python 3, a notification is triggered, which prompts the user to install XCode and developer tools.
alias#
如果py脚本开头没有指定 Shebang - #!/usr/bin/env python3，则 vscode Run Code 执行 python -u test.py，可能提示找不到 python 命令。
macOS 自 Monterey（April 2022）后移除了 Python 2.7。
macOS 在安装 Xcode command-lines tools 时会安装 Python3，默认路径为 /usr/bin/python3，而使用 brew 安装的 python3 的路径一般为 /usr/local/bin/python3。
既然 python（2.7）不再，可考虑在 ~/.zshrc 中添加 alias python=/usr/bin/python3，这样 python 指向系统自带的 python3 版本，作为 fallback。