brew info python
python: stable 3.6.4 (bottled), devel 3.7.0b1, HEAD
Interpreted, interactive, object-oriented programming language
https://www.python.org/
/usr/local/Cellar/python/3.6.4_3 (64B)
Built from source
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/python.rb
brew info python@2
python@2: stable 2.7.14 (bottled), HEAD [keg-only]
Interpreted, interactive, object-oriented programming language
https://www.python.org/
Not installed
From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/python@2.rb
https://github.com/Homebrew/homebrew-core/commit/788b65e645bb342e82946b52173997cd00c322ac
python2 变成了 python@2 https://github.com/Homebrew/homebrew-core/commit/57cd0561a81fc6edc7155b9ff4760e0debddc777
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