我按照以下步骤进行了操作：
1）
1）
$ sudo pip install psycopg2
这给我带来了以下错误。Downloading/unpacking psycopg2
Running setup.py egg_info for package psycopg2
no previously-included directories found matching 'doc/src/_build'
Installing collected packages: psycopg2
Running setup.py install for psycopg2
building 'psycopg2._psycopg' extension
llvm-gcc-4.2 -fno-strict-aliasing -fno-common -dynamic -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -mno-fused-madd -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -fwrapv -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch i386 -arch x86_64 -pipe -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4.3 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x090004 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -I. -I/usr/include -I/usr/include/postgresql/server -c psycopg/psycopgmodule.c -o build/temp.macosx-10.7-intel-2.7/psycopg/psycopgmodule.o
unable to execute llvm-gcc-4.2: No such file or directory
error: command 'llvm-gcc-4.2' failed with exit status 1
Complete output from command /usr/bin/python -c "import setuptools;__file__='/Users/boltellinfomedia/mukul/mukul/build/psycopg2/setup.py';exec(compile(open(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --single-version-externally-managed --record /tmp/pip-8NaS72-record/install-record.txt:
running install
running build
running build_py
running build_ext
building 'psycopg2._psycopg' extension
llvm-gcc-4.2 -fno-strict-aliasing -fno-common -dynamic -g -Os -pipe -fno-common -fno-strict-aliasing -fwrapv -mno-fused-madd -DENABLE_DTRACE -DMACOSX -DNDEBUG -Wall -Wstrict-prototypes -Wshorten-64-to-32 -DNDEBUG -g -fwrapv -Os -Wall -Wstrict-prototypes -DENABLE_DTRACE -arch i386 -arch x86_64 -pipe -DPSYCOPG_DEFAULT_PYDATETIME=1 -DPSYCOPG_VERSION="2.4.3 (dt dec pq3 ext)" -DPG_VERSION_HEX=0x090004 -DPSYCOPG_EXTENSIONS=1 -DPSYCOPG_NEW_BOOLEAN=1 -DHAVE_PQFREEMEM=1 -I/System/Library/Frameworks/Python.framework/Versions/2.7/include/python2.7 -I. -I/usr/include -I/usr/include/postgresql/server -c psycopg/psycopgmodule.c -o build/temp.macosx-10.7-intel-2.7/psycopg/psycopgmodule.o
unable to execute llvm-gcc-4.2: No such file or directory
error: command 'llvm-gcc-4.2' failed with exit status 1
----------------------------------------
Command /usr/bin/python -c "import setuptools;__file__='/Users/boltellinfomedia/mukul/mukul/build/psycopg2/setup.py';exec(compile(open(__file__).read().replace('\r\n', '\n'), __file__, 'exec'))" install --single-version-externally-managed --record /tmp/pip-8NaS72-record/install-record.txt failed with error code 1
Storing complete log in /Users/boltellinfomedia/.pip/pip.log
2) 接着我在网上搜索了安装llvm-gcc-4.2，从这个链接得知需要安装Xcode
又从这个链接中得知可以通过macports安装psycopg2但是从这个链接中得知我仍然需要Xcode。
3) 最后我试着从苹果商店安装Xcode，它下载了1.6 GB的文件并且显示已经安装在我的系统中。下面是截图：
![macports installed image][1]
4) 然后我试着通过可从链接获得的dmg文件安装macports，但是提示我尚未安装Xcode。下面是截图：![when trying to install macport, xcode not installed message appears][2]