I'm having problem while installing matplotlib. I'm using Mavericks and it complains about a deprecated NumPy API both installing via pip and installing from source (following the instructions here https://github.com/matplotlib/matplotlib/blob/master/README.osx):

In file included from src/_macosx.m:1:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/Cocoa.framework/Headers/Cocoa.h:12:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/Foundation.framework/Headers/Foundation.h:10:
In file included from /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSArray.h:5:
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.8.sdk/System/Library/Frameworks/Foundation.framework/Headers/NSObject.h:76:1: error: duplicate interface definition for class 'NSObject'
@interface NSObject <NSObject> {
^
/usr/include/objc/NSObject.h:50:12: note: previous definition is here
@interface NSObject <NSObject> {^
In file included from src/_macosx.m:5:
In file included from /Users/se7entyse7en/Envs/datascience/lib/python2.7/site-packages/numpy/core/include/numpy/arrayobject.h:4:
In file included from /Users/se7entyse7en/Envs/datascience/lib/python2.7/site-packages/numpy/core/include/numpy/ndarrayobject.h:17:
In file included from /Users/se7entyse7en/Envs/datascience/lib/python2.7/site-packages/numpy/core/include/numpy/ndarraytypes.h:1761:
/Users/se7entyse7en/Envs/datascience/lib/python2.7/site-packages/numpy/core/include/numpy/npy_1_7_deprecated_api.h:15:2: warning: "Using deprecated NumPy API, disable it by "          "#defining NPY_NO_DEPRECATED_APINPY_1_7_API_VERSION" [-W#warnings]
#warning "Using deprecated NumPy API, disable it by " \^
1 warning and 1 error generated.
error: command 'clang' failed with exit status 1

After that it exists without having completed the installation. I have already installed both libpng and freetype using brew, and I also already have installed both NumPy and SciPy via pip:

numpy==1.8.2
scipy==0.14.0

Ok, I solved the issue also thanks to flebool. In the folder

/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs

I had both MacOSX10.9.sdk and MacOSX10.8.sdk and I didn't know if they should exists both. I had Mavericks so I thought that maybe MacOSX10.8.sdk could be the problem. I deleted it and I managed to install matplotlib from source succesfully.