chins-MBP:~ chinvincent$ pip list
Package Version
-------------------------------------- --------
altgraph 0.10.2
backports-abc 0.5
bdist-mpkg 0.5.0
bonjour-py 0.3
click 6.7
distribute 0.7.3
Flask 1.0.2
futures 3.2.0
itsdangerous 0.24
Jinja2 2.10
macholib 1.5.1
MarkupSafe 1.0
matplotlib 1.3.1
modulegraph 0.10.4
nose 1.3.7
numpy 1.8.0rc1
pip 10.0.1
py2app 0.7.3
pyobjc-core 2.5.1
pyobjc-framework-Accounts 2.5.1
pyobjc-framework-AddressBook 2.5.1
pyobjc-framework-AppleScriptKit 2.5.1
pyobjc-framework-AppleScriptObjC 2.5.1
pyobjc-framework-Automator 2.5.1
pyobjc-framework-CFNetwork 2.5.1
pyobjc-framework-Cocoa 2.5.1
pyobjc-framework-Collaboration 2.5.1
pyobjc-framework-CoreData 2.5.1
pyobjc-framework-CoreLocation 2.5.1
pyobjc-framework-CoreText 2.5.1
pyobjc-framework-DictionaryServices 2.5.1
pyobjc-framework-EventKit 2.5.1
pyobjc-framework-ExceptionHandling 2.5.1
pyobjc-framework-FSEvents 2.5.1
pyobjc-framework-InputMethodKit 2.5.1
pyobjc-framework-InstallerPlugins 2.5.1
pyobjc-framework-InstantMessage 2.5.1
pyobjc-framework-LatentSemanticMapping 2.5.1
pyobjc-framework-LaunchServices 2.5.1
pyobjc-framework-Message 2.5.1
pyobjc-framework-OpenDirectory 2.5.1
pyobjc-framework-PreferencePanes 2.5.1
pyobjc-framework-PubSub 2.5.1
pyobjc-framework-QTKit 2.5.1
pyobjc-framework-Quartz 2.5.1
pyobjc-framework-ScreenSaver 2.5.1
pyobjc-framework-ScriptingBridge 2.5.1
pyobjc-framework-SearchKit 2.5.1
pyobjc-framework-ServiceManagement 2.5.1
pyobjc-framework-Social 2.5.1
pyobjc-framework-SyncServices 2.5.1
pyobjc-framework-SystemConfiguration 2.5.1
pyobjc-framework-WebKit 2.5.1
pyOpenSSL 0.13.1
pyparsing 2.0.1
python-dateutil 1.5
pytz 2013.7
scipy 0.13.0b1
setuptools 18.5
singledispatch 3.4.0.3
six 1.4.1
tornado 5.0.2
Werkzeug 0.14.1
xattr 0.6.4
zope.interface 4.1.1
chins-MBP:~ chinvincent$ sudo pip install requests
The directory "/Users/chinvincent/Library/Caches/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 "/Users/chinvincent/Library/Caches/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.
Requirement already satisfied: requests in ./Library/Python/2.7/lib/python/site-packages (2.18.4)
Requirement already satisfied: idna<2.7,>=2.5 in ./Library/Python/2.7/lib/python/site-packages (from requests) (2.6)
Requirement already satisfied: urllib3<1.23,>=1.21.1 in ./Library/Python/2.7/lib/python/site-packages (from requests) (1.22)
Requirement already satisfied: certifi>=2017.4.17 in ./Library/Python/2.7/lib/python/site-packages (from requests) (2018.4.16)
Requirement already satisfied: chardet<3.1.0,>=3.0.2 in ./Library/Python/2.7/lib/python/site-packages (from requests) (3.0.4)
my installation package is obviously installed, but why doesn"t pip list always exist? I don"t know why I"ve been confused for a long time, ask for guidance!