ArcGIS API for Python... What is Where... part I

07-30-2017 07:27 PM
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ArcGIS API for Python  ... version 1.2.0

Another cleverly named product to provide more clarity to the other named kindred... ArcGIS for Desktop, ArcGIS Pro, Arc... etcetera.  The link to the help is here.  The ability to work with Jupyter notebooks, NumPy, SciPy and Arcpy is touted and welcomed (...and there is something about web mapping and stuff as well).

Where stuff is

Locating ArcGIS in your installation path, depends on how you installed it... for a single user (aka no sharesies) or for anyone.  This describes the single user situation.

To begin, import the module and check its __path__ and __file__ property.  My installation path is in an ArcPro folder that I created... yours will differ, but beyond the base folder, everything should be the same.

Basic import______________________________________________________________________

In [1]: import arcgis
In [2]: arcgis.__path__
Out[2]: ['C:\\ArcPro\\bin\\Python\\envs\\arcgispro-py3\\lib\\site-packages\\arcgis']

In [3]: arcgis.__file__

Out[3]: 'C:\\ArcPro\\bin\\Python\\envs\\arcgispro-py3\\lib\\site-packages\\arcgis\\'


The file is read during the import and a whole load of imports are done to cover access to pretty well all available modules contained in the ArcGIS path.

If you only want to work with the geometry or Pandas related functionality, you can import the SpatialDataFrame class directly.


In [1]: from arcgis import SpatialDataFrame as sdf

# ---- or ----

In [1]: from arcgis.features._data.geodataset import SpatialDataFrame as sdf

In [2]: sdf.__module__  # to confirm the path

Out[2]: 'arcgis.features._data.geodataset.geodataframe'


The SpatialDataFrame class is pretty well all that is in script.

Another useful call within that class is one to from_featureclass and to_featureclass which can be obtained by a variety of other imports or by a direct call to the io module's

Featureclass access________________________________________________________________

In [3]: from import from_featureclass, to_featureclass

# ---- or ----

In [4] from arcgis.features._data.geodataset import io


If you prefer the module.function method of calling, the option in ln [4] can be used to convert a featureclass to a SpatialDataFrame.

The Reveal________________________________________________________________________

In [5] fc0 = r'drive:\your_space_free_path\your_geodatabase.gdb\polygon'

In [6] a = io.from_featureclass(fc0)

In [7] print("\nSpatialDataFrame 'a' \n{}".format(a))  # ---- the sdf contents ----

SpatialDataFrame 'a'
   OBJECTID  Id Text_fld                                              SHAPE
0         1   1     None  {'rings': [[[300020, 5000000], [300010, 500000...
1         2   2        C  {'rings': [[[300010, 5000020], [300010, 500001...
2         3   3        A  {'rings': [[[300010, 5000010], [300010, 500002...

ln [8] type(a)

Out[8]: <class 'arcgis.features._data.geodataset.geodataframe.spatialdataframe'>


Behind the Scenes

Great so far... BUT when you delve deeper into what is going on under the hood, you will find out that the from_featureclass method...

  1. imports the SpatialDataFrame class
  2. uses arcpy.da.SearchCursor to convert the featureclass into lists of
    1. values (non-geometry fields)
    2. geometry (geometry field)
  3. the value fields are then converted to a pandas dataframe (pd.DataFrame)
  4. the dataframe in step 3 is then used with the geometry values to produce a SpatialDataFrame modelled after a Pandas dataframe.

Final Comments

So... in conclusion, an arcpy.da searchcursor is used to get all the necessary geometry and attribute data then ultimately to a SpatialDataFrame ... which is like a Pandas dataframe ... but it is geometry enabled.

Sort of like geopandas... (geopandas on GitHub) but relying on arc* functionality and code for the most part.

More to Come

There will be more posts as I have time... the next post... Geometry.... part II

About the Author
Retired Geomatics Instructor at Carleton University. I am a forum MVP and Moderator. Current interests focus on python-based integration in GIS. See... Py... blog, my GeoNet blog...