python-ssas

Prerequisites:

• Good working knowledge of:
  • Microsoft SQL Server Analysis Services (Tabular models)
  • Python (specifically pandas)
• Some knowledge required:
  • General Microsoft .Net familiarity

Motivation:

I’ve been working for some time analyzing data using two unrelated tools – Python (primarily pandas), and DAX in Microsoft’s Tabular models. They are very different – Python is open source, Microsoft’s products are (obviously) not. It was frustrating to not be able to merge them. If I wanted to get data from a DAX data model into a Pandas dataframe, I would typically need to first export it to a file (like CSV) and then read it from there.

Also, I wanted a way to programatically "refresh" the data model (called "processing" it) from Python.

Solution:

Inspired by @akavalar's great post, I discovered a nice workaround:

• DAX models (or any Analysis Services model) have several .Net APIs, see here for the Microsoft documentation
• Also, there is a fantastic Python library called Pythonnet that enables near seamless integration between Python and .Net. This is for the mainstream Python, called CPython, and not to be confused with the .Net implementation of Python which is called IronPython.

Using these ingredients, I created my ssas_api.py module with some utilities that I use frequently. Note that this just uses the parts of the APIs that I needed; there is a wealth more available, just dig through the documentation.

Note: I've only been using Azure Analysis Services, so the code is designed for that regarding the URL of the server and authentication string.

I haven't found anything like this online, so feel free to use it.

Getting The Required .Net Libraries

ssas_api.py requires 2 specific DLLs to work:

• Microsoft.AnalysisServices.Tabular.dll
• Microsoft.AnalysisServices.AdomdClient.dll

These are usually already installed on most users' computers if they are using any of the Microsoft tools that interact with DAX, such as Excel, Power BI Desktop, or SSMS. By default, they are installed in C:\Windows\Microsoft.NET\assembly\GAC_MSIL.

In cases when they aren't installed, or if the user wants to install them manually, here is a quick and conveinent way to do so using PowerShell (requires Admin access)

# Register NuGet provider if not yet registered
Install-PackageProvider -Name "Nuget" -Force
Register-PackageSource -Name MyNuGet -Location https://www.nuget.org/api/v2 -ProviderName NuGet -Trusted -Force

# Install the packages
Install-Package Microsoft.AnalysisServices.retail.amd64
Install-Package Microsoft.AnalysisServices.AdomdClient.retail.amd64 

If installing via NuGet here is a Python snippet that will help with managing the path where it installs it to (C:/Program Files/PackageManagement/NuGet/Packages/Microsoft.AnalysisServices):

# dll paths setup, NuGet puts them here
base = "C:/Program Files/PackageManagement/NuGet/Packages/Microsoft.AnalysisServices"
_version = "19.4.0.2"  # at time of this writing
AMO_PATH = f"{base}.retail.amd64.{_version}/lib/net45/Microsoft.AnalysisServices.Tabular.dll"
ADOMD_PATH = f"{base}.AdomdClient.retail.amd64.{_version}/lib/net45/Microsoft.AnalysisServices.AdomdClient.dll"

Quickstart

In [1]: import ssas_api
   ...: 
   ...: conn = ssas_api.set_conn_string(
   ...:     server='<YOUR_SERVER>',
   ...:     db_name='<YOUR_DATABASE>',
   ...:     username='<USERNAME>',
   ...:     password='<PASSWORD>'
   ...: )

In [2]: dax_string = '''
   ...: //any valid DAX query
   ...: EVALUATE
   ...: CALCULATETABLE(MyTable)
   ...: '''

In [3]: df = ssas_api.get_DAX(connection_string=conn, dax_string=dax_string)