RPyGeo Query -- probably easy

Hi,

yes, the quotes are indeed tricky... The challenge is to provide the 
correct mix of escaped and un-escaped single and double quotes to Python 
/ ArcGIS as in this Python example:

gp.select_analysis("nfroads.shp", "paved.shp",
     ' "ROAD_CLASS" = \'PAVED\' ')

In order to achieve this, the backslashes in \' have to be escaped 
themselves, otherwise R will interpret them as escape symbols. After 
all, \' ends up being coded as \\\' in R. Also, double double-quotes 
have to be avoided; the quote.args argument of rpygeo.geoprocessor can 
be used to suppress the outermost double quotes, single quotes can be 
used explicitly instead: " ' sqlquery ' "

So here are two solutions:


env = rpygeo.build.env( workspace = "C:/TEMP",
               overwriteoutput = TRUE )

rpygeo.geoprocessor("select_analysis",
     list( "nfroads.shp", "paved.shp",
           " ' \"ROAD_CLASS\" = \\\'PAVED\\\' ' "),
     clean.up = FALSE, quote.args = c(T,T,F),
     env = env)


# alternative:

rpygeo.geoprocessor("select_analysis('nfroads.shp','paved.shp','\"ROAD_CLASS\"=\\\'PAVED\\\'')",
      env = env, clean.up = FALSE)


I hope this helps...

Cheers
  Alex

Andrew, thanks for your reply!
I tried exactly your command, but still the resulting rpygeo.py file
contains the following line:

gp.select_analysis( "nfroads.shp", "paved.shp", "\"ROAD_CLASS\" = 'PAVED' "
)

So the \"ROAD_CLASS\" = 'PAVED' is still surrounded by double quotes ("). I
have tried many different Python commands, but the only one working for me
is:

gp.select_analysis( "nfroads.shp", "paved.shp", ' "ROAD_CLASS" = \'PAVED\' '
)

Somehow I need to instruct RPyGeo to leave away the double quotes and
replace them by single quotes.

Kind regards, Maarten



Maarten
 
I'm not sure about the single quotes but possibly you could add an extra
special character break (the \ ) to indicate to python that the double
quotes surrounding your field name are not the end of a string.  You could
try the following code:
 
rpygeo.geoprocessor("select_analysis", c("nfroads.shp", "paved.shp", '
\\"ROAD_CLASS\\" = \'PAVED\' '), py.file= "rpygeo.py", working.directory =
 wrkspc, env = myenv, clean.up = FALSE)

 
Best Regards
 
Andrew
 
Dr Andrew Crowe
 
Lancaster Environment Centre
Lancaster University
Lancaster    LA1 4YQ
UK

Alexander Brenning
brenning at uwaterloo.ca - T +1-519-888-4567 ext 35783
Department of Geography and Environmental Management
University of Waterloo
200 University Ave. W - Waterloo, ON - Canada N2L 3G1
http://www.fes.uwaterloo.ca/geography/faculty/brenning/