call python with system() in R to run a python script emulating the python console

Question

I want to pass a chunk of Python code to Python in R with something like system(\'python ...\'), and I\'m wondering if there is an easy way to emulate the pytho

Answer 1

My work around for this problem is defining my own functions that paste in parameters, write out a temporary .py file, and them execute the python file via a system call. Here is an example that calls ArcGIS's Euclidean Distance function:

py.EucDistance = function(poly_path,poly_name,snap_raster,out_raster_path_name,maximum_distance,mask){

    py_path = 'G:/Faculty/Mann/EucDistance_temp.py'
    poly_path_name = paste(poly_path,poly_name, sep='')

    fileConn<-file(paste(py_path))
    writeLines(c(
        paste('import arcpy'),
        paste('from arcpy import env'),
        paste('from arcpy.sa import *'),
        paste('arcpy.CheckOutExtension("spatial")'),

        paste('out_raster_path_name = "',out_raster_path_name,'"',sep=""),
        paste('snap_raster = "',snap_raster,'"',sep=""),
        paste('cellsize =arcpy.GetRasterProperties_management(snap_raster,"CELLSIZEX")'),
        paste('mask = "',mask,'"',sep=""),
        paste('maximum_distance = "',maximum_distance,'"',sep=""),
        paste('sr = arcpy.Describe(snap_raster).spatialReference'),

        paste('arcpy.env.overwriteOutput = True'),
        paste('arcpy.env.snapRaster = "',snap_raster,'"',sep=""),
        paste('arcpy.env.mask = mask'),
        paste('arcpy.env.scratchWorkspace ="G:/Faculty/Mann/Historic_BCM/Aggregated1080/Scratch.gdb"'),
        paste('arcpy.env.outputCoordinateSystem = sr'),


        # get spatial reference for raster and force output to that
        paste('sr = arcpy.Describe(snap_raster).spatialReference'),
        paste('py_projection = sr.exportToString()'),     
        paste('arcpy.env.extent = snap_raster'),
        paste('poly_name = "',poly_name,'"',sep=""),
        paste('poly_path_name = "',poly_path_name,'"',sep=""),

        paste('holder = EucDistance(poly_path_name, maximum_distance, cellsize, "")'),
        paste('holder = SetNull(holder < -9999, holder)'),
        paste('holder.save(out_raster_path_name) ')

    ), fileConn, sep = "\n")
    close(fileConn)

    system(paste('C:\\Python27\\ArcGIS10.1\\python.exe', py_path))
}