configuraiton Xcode (mac os X) pour Python3,pb chois de l'exécutable

salut à tous
j'ai Python 3 installé
j'ai suivi à la lettre les instructions suivantes (lien original perdu, voir fin de ce message)
dans le point 15, impossible de sélectionner python3 comme demandé car c'est grisé. J'ai pris, à l'aveuglette, python3.3-32 qui, lui, n'est pas grisé
ensuite, lorsque je fais Run pour un code simplissime j'ai :

Xcode cannot run using the selected destination.
Choose a destination with a supported architecture in order to run on this system.

du coup je bloque…

Vincent

instructions trouvées sur internet
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1. Open Xcode 4 or Xcode 5. The instructions for either are the same.
2. In the menu bar, click "File" → "New" → "New Project…".
3. Select "Other" under "Mac OS X".
4. Select "External Build System" and click "Next".
5. Enter the product name, organization name, and company identifier.
6. For the "Build Tool" field, type in /usr/local/bin/python3 and then click "Next". Note that this assumes you have Python installed in the typical location(s). if you are unsure as to where your Python executables are enter these commands into Terminal: which python3 (it's ok)
7. Choose where to save it and click "Create".
8. In the menu bar, click "File" → "New" → "New File…".
9. Select "Other" under "Mac OS X".
10. Select "Empty" and click "Next".
11. Navigate to the project folder (it will not work, otherwise), enter the name of the Python file (include the ".py" extension), and click "Save".
12. In the menu bar, click "Product" → "Scheme" → "Edit Scheme…".
13. Click "Run" in the left column.
14. In the "Info" tab, click the "Executable" field and then click "Other…".
15. Navigate to the executable from Step 6. You may need to use ⇧⌘G to type in the directory if it is hidden.
16. Select the executable and click "Choose".
17. For the "Debugger" field, select "None".
18. In the "Arguments" tab, click the "Expand Variables Based On" field and select the target that is named the same as your project.
19. Click the "+" icon under "Arguments Passed On Launch". You may have to expand that section by clicking on the triangle pointing to the right.
20. Type in $(SRCROOT)/ (or $(SOURCE_ROOT)/) and then the name of the Python file you want to test. Remember, the Python program must be in the project folder. Otherwise, you will have to type out the full path (or relative path if it's in a subfolder of the project folder) here. If there are spaces anywhere in the full path, you must include quotation marks at the beginning and end of this.
21. Click "OK".
22. Start coding.