I'm curious to know whether ArcGIS Desktop 10.0 will support newer versions of Python than 2.6. And for that matter newer versions of NumPy (ie, 1.4, 1.5 etc). I'm sure that this documentation is on the ESRI site somewhere, but I can't find it.

I have found that ArcGIS Desktop 10.0 will respect an existing Python 2.6 install as long as you have Numpy 1.3.0 installed (ref), and I'm guessing, at least until Numpy 1.5.0 is out and supporting Python 3, then no Python 3 for ArcGIS, but I'd still be interested to know if upgrading is possible when it's available.

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    For the record, ArcGIS 10.0 comes with Python 2.6.5
    – fmark
    Aug 2, 2010 at 1:55
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    you can still try. just because something is not 'supported doesn't mean it won't work. Let us know what you kind out.
    – micahwilli
    Feb 7, 2011 at 7:38

4 Answers 4


Nope, one version of Python per release of ArcGIS. The reason for this is simple: most of the magic happens in a C extension (arcgisscripting). The C APIs change from version to version, and that DLL isn't going to play nice in other versions of Python.

However, every time the main Python.org site releases a security fix (2.6.X), those are binary compatible and can be installed.


Nope. An Esri staff member says no in a forum reponse post:

ArcGIS 10 final will ship with one and only one version of python. At Pre-release we have 2.6.2. Most probably for 10 final we will have 2.6.5. Having said that, ArcGIS 10 will work with any 2.6 version of python. So say 6 months from now, we have Python 2.6.6 released but ArcGIS is using only 2.6.5, you can safely install Python 2.6.6 and ArcGIS will work ok. Note that this compatibility works only with a major release of Python. In other words ArcGIS 10 will never work with Python 2.7 or Python 3.1 or any other major release of python. Only Python 2.6 is supported.

  • Ah well, worth a try.
    – om_henners
    Aug 2, 2010 at 9:54
  • Bear in mind that post is 2 years old. You know that what was true 2 years ago and for ArcGIS 10.0 may not necessarily still be true for ArcGIS 10.x in the future. Jan 29, 2012 at 23:46
  • ArcGIS 10.2.2 is still at Python 2.7.x. However the new ArcGIS Pro desktop application (to be released in mid-2014) uses Python 3.4 - and uses the same GP environment (toolboxes) as Desktop 10x. So ArcGIS scripters should work on their skills writing code that is 2.7/3.4 compatible -- which BTW isn't that difficult. May 23, 2014 at 17:33

I think it is important to make this Q&A cover not just ArcGIS Desktop 10.0, Python 2.7 and Python 3.1, but also to incorporate the latest versions of desktop products from the ArcGIS platform and the Python programming language.

For Python support in the (currently) latest desktop products from the ArcGIS platform I think you should consider:

If you do need to use Python outside of ArcGIS Pro, download the Python setup from My Esri. This installation will install Python 3.4.1, all third-party requirements required by ArcGIS Pro, and an ArcGISPro.pth file that is used to identify all ArcGIS Pro folders required to run ArcPy.

ArcGIS for Desktop geoprocessing tools require that Python 2.7.x and Numerical Python 1.7.x are installed. If the ArcGIS for Desktop setup does not find either Python 2.7.x or Numerical Python (NumPy) 1.7.xinstalled on the target computer, Python 2.7.8 and Numerical Python 1.7.1 will be installed during a complete installation of ArcGIS 10.3.x.


I don't know about arc10, but in all ArcGIS 9 versions you could upgrade python to the latest and greatest version with a few simple steps. This is an unsupported configuration, see ESRI knowledgebase article 31912. Please report back if this works for you with ArcGIS 10.

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    This only works for releases of the same major.minor version (ie going from 2.6.3 to 2.6.5 in ArcGIS 10). This ABSOLUTELY WILL NOT WORK RELIABLY going from 2.5.X to 2.6.X in ArcGIS because there are some binary incompatibilities between Python versions' APIs. If it does work, you are just lucky. Anything long-running will likely have subtle and dangerous data corruption over time. Sep 28, 2010 at 3:13
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    I welcome explicit examples/demonstrations of incompatibilites and/or data corruption (honestly, I really do). I've upgraded across major python versions for several years and not (yet) encountered any significant issues. On the other hand I've seen some pretty significant data corruption from arcgis itself. So, it's a risk I'm willing to take, but with suitable caution and due diligence. Sep 28, 2010 at 16:22

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