注意:
python语言大小写非常敏感，利用Mac终端查看版本号必须用大写的python -V
另外cocoapods是利用ruby语言写的，不是python语言。
$python -V
Python 2.7.10
如果不小心错写成小写的python -v就会打印如下一大堆信息，让人误以为Mac系统没有预装python呢？
$python -v
# installing zipimport hook
import zipimport # builtin
# installed zipimport hook
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site.py
import site # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/os.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/os.py
import os # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/os.pyc
import errno # builtin
import posix # builtin
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/posixpath.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/posixpath.py
import posixpath # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/posixpath.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/stat.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/stat.py
import stat # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/stat.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/genericpath.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/genericpath.py
import genericpath # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/genericpath.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/warnings.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/warnings.py
import warnings # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/warnings.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/linecache.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/linecache.py
import linecache # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/linecache.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/types.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/types.py
import types # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/types.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/UserDict.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/UserDict.py
import UserDict # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/UserDict.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_abcoll.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_abcoll.py
import _abcoll # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_abcoll.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/abc.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/abc.py
import abc # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/abc.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_weakrefset.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_weakrefset.py
import _weakrefset # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_weakrefset.pyc
import _weakref # builtin
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy_reg.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy_reg.py
import copy_reg # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy_reg.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/traceback.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/traceback.py
import traceback # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/traceback.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sysconfig.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sysconfig.py
import sysconfig # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sysconfig.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.py
import re # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/re.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_compile.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_compile.py
import sre_compile # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_compile.pyc
import _sre # builtin
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_parse.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_parse.py
import sre_parse # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_parse.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_constants.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_constants.py
import sre_constants # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/sre_constants.pyc
dlopen("/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/_locale.so", 2);
import _locale # dynamically loaded from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/_locale.so
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_sysconfigdata.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_sysconfigdata.py
import _sysconfigdata # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_sysconfigdata.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_osx_support.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_osx_support.py
import _osx_support # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/_osx_support.pyc
import encodings # directory /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/__init__.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/__init__.py
import encodings # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/__init__.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/codecs.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/codecs.py
import codecs # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/codecs.pyc
import _codecs # builtin
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/aliases.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/aliases.py
import encodings.aliases # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/aliases.pyc
# /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/utf_8.pyc matches /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/utf_8.py
import encodings.utf_8 # precompiled from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/encodings/utf_8.pyc
Python 2.7.10 (default, Oct 23 2015, 19:19:21)
[GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.0.59.5)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
dlopen("/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/readline.so", 2);
import readline # dynamically loaded from /System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/lib-dynload/readline.so
>>>