topic Re: If else statement not working in Python in Python Questions

If else statement not working in Python

MollyWatson — Tue, 05 Feb 2013 17:56:39 GMT

Hello,

I have a Python script to generate an automated mapbook. I want to be able to adjust the data frame scale based on the size of the parcel. My if/else statement is not working. I think it's because it's not recognizing the acreage field in the Parcels table and/or it says it cannot combine a string with an integer. Here is my sample where I create the map document, select the parcel based on user parameters, and zoom to selected feature. The parcels layer is stored in an SDE database.

# Process: Create Mapbook Document, Data Frame, and Layer Objects
mxd = mapping.MapDocument(r"V:\gislu\_BasemapMXD\10.1 MXDS\PreApp_Location.mxd")
df = mapping.ListDataFrames(mxd, "PreApp Location")[0]
Layer = mapping.ListLayers(mxd, "Parcels", df)[0]

#Process: Select Layer by Attributes
whereClause = "\"ADDRNO\" = " + NUMBER + " AND \"ADDRSTREET\" = '" + STREET + "'"
arcpy.AddMessage("SELECTING: " + whereClause)
arcpy.SelectLayerByAttribute_management (Layer, "NEW_SELECTION", whereClause)
arcpy.AddMessage(arcpy.GetCount_management(Layer).getOutput(0))

#Process: Update the mapbook display in ArcMap
df.zoomToSelectedFeatures()
for Layer in mapping.ListLayers(mxd, "Parcels", df):
if [acreage] < str(153):
df.scale = 5000
else:
df.scale = 9000
arcpy.RefreshActiveView()
arcpy.RefreshTOC()
legend = mapping.ListLayoutElements(mxd, "LEGEND_ELEMENT", "Legend")[0]
legend.autoAdd = True

Re: If else statement not working in Python

markdenil — Tue, 05 Feb 2013 18:47:04 GMT

There seem to be a number of issues here.
For example, I don't think you can get to a feature attribute by querying a layer object.
Nor can presenting a field name to the layer get you anywhere: layer objects don't have fields
They do have names and sources and max scales and whatnot.
you need to access the (lone) feature you expect to find in that layer to test the field's value.

As well, are the values in [acreage] really strings?
You present it with a string (str(153), which is really "153")
but expect it to resolve a less-than test...
This likely causes your "string with an integer" error.

int([acreage]) < "153" is more likely to work, if [acreage] really is a string....

(edit -> oops, that is right, int([acreage]) < 153 is what I meant.... )

Re: If else statement not working in Python

Zeke — Tue, 05 Feb 2013 20:16:34 GMT

Also, please enclose your code in code tags.
I'd try

 int([acreage]) < 153

, without the quotes around 153.

Re: If else statement not working in Python

curtvprice — Tue, 05 Feb 2013 20:20:14 GMT

# Process: Create Mapbook Document, Data Frame, and Layer Objects mxd = mapping.MapDocument(r"V:\gislu\_BasemapMXD\10.1 MXDS\PreApp_Location.mxd") df = mapping.ListDataFrames(mxd, "PreApp Location")[0] Layer = mapping.ListLayers(mxd, "Parcels", df)[0]  #Process: Select Layer by Attributes whereClause = "\"ADDRNO\" = " + NUMBER + " AND \"ADDRSTREET\" = '" + STREET + "'" arcpy.AddMessage("SELECTING: " + whereClause) arcpy.SelectLayerByAttribute_management (Layer, "NEW_SELECTION", whereClause) arcpy.AddMessage(arcpy.GetCount_management(Layer).getOutput(0))       #Process: Update the mapbook display in ArcMap df.zoomToSelectedFeatures() for Layer in mapping.ListLayers(mxd, "Parcels", df):     if [acreage] < str(153):         df.scale = 5000     else:         df.scale = 9000 arcpy.RefreshActiveView() arcpy.RefreshTOC() legend = mapping.ListLayoutElements(mxd, "LEGEND_ELEMENT", "Legend")[0] legend.autoAdd = True

Please note the [post=166129]use of the [noparse]

[/noparse] block[/post] to format your code in the forum.

Mark is correct that you can't get the value this way. Do you want the total acreage of the selected features? You could determine that using the Summary Statistics tool. If you only have one parcel selected, you could get the acreage value out of the table using a search cursor on your layer.

What if your parcel is long and skinny? Seems to me a safer approach would be to examine the df.scale after you zoom to selected and decide based on that which standard scale to use:

if df.scale <= 5000:   df.scale = 5000 elif df.scale <= 9000:   df.scale = 9000

Re: If else statement not working in Python

MollyWatson — Tue, 19 Feb 2013 14:04:48 GMT

Thank you everyone! The idea about using if/elif statement for the data frame scale worked and was the easiest route to go! I hadn't thought about it that way so thanks for the good idea.