topic Re: If-then-else in Python Questions

If-then-else

CCWeedcontrol — Thu, 07 Jan 2016 19:11:25 GMT

I need help setting up an if-than-else within a if-else statement. I need the code i need to check if selected features has any text inside the AddressID field if it does have any text inside the field i need it to by pass the with arcpy.da.SearchCursor and the with arcpy.da.UpdateCursor and move on to the next process. if doesn't have any text inside the field i need it to preform the with arcpy.da.SearchCursor and the with arcpy.da.UpdateCursor. I would appreciate any help.

import arcpy, os  
from arcpy import env  
env.workspace = r"C:\temp\python\test.gdb"  
  
arcpy.env.qualifiedFieldNames = False          
arcpy.env.overwriteOutput = True    
  
BldSelection = "BuildingFootprints"           
Bld = arcpy.env.workspace + os.sep + "BuildingFootprints" #target point feature class    
    
BldCount = int(arcpy.GetCount_management(Bld).getOutput(0))    
    
dsc = arcpy.Describe(BldSelection)     
selection_set = dsc.FIDSet             
if len(selection_set) == 0:           
    print "There are no features selected"      
                 
elif BldCount >= 1:    
    #Gets the highest AddressID and calculates new point to assign new highest AddressID    
    Bld_list = []          
    with arcpy.da.SearchCursor(Bld, ["Bld_ID"]) as cursor:          
        for row in cursor:  
            try:          
                if "Bld" in row[0]:  
                      
                    Bld_list.append(int(row[0].strip("Bld")))             
            except TypeError:          
                pass                  
    del cursor          
  
    print Bld_list  
          
    Bld_list.sort()          
    Bld_ID = Bld_list[-1] + 1          
        
    
    with arcpy.da.UpdateCursor(BldSelection, "Bld_ID") as rows:           
        for row in rows:              
            row[0] = 'Bld' + str(Bld_ID)  
            Bld_ID += 1                      
            rows.updateRow(row)      
        del row           
        del rows

Re: If-then-else

WesMiller — Thu, 07 Jan 2016 19:36:18 GMT

Why not use Make Feature Layer—Help | ArcGIS for Desktop and remove those that have data before you start your cursor.

MakeFeatureLayer_management (in_features, out_layer, "Field" > '')

Re: If-then-else

CCWeedcontrol — Thu, 07 Jan 2016 19:47:33 GMT

I am not sure i follow, add MakeFeatureLayer_management (in_features, out_layer, "Field" > '') in between lines 20 & 21?

Re: If-then-else

WesMiller — Sun, 12 Dec 2021 06:47:48 GMT

Something similar to below

import arcpy, os    
from arcpy import env    
env.workspace = r"C:\temp\python\test.gdb"    
    
arcpy.env.qualifiedFieldNames = False            
arcpy.env.overwriteOutput = True      
    
BldSelection = "BuildingFootprints"             
Bld = arcpy.env.workspace + os.sep + "BuildingFootprints" #target point feature class      


bldlyr = arcpy.MakeFeatureLayer_management(Bld,"Building_layer","AddressID > ''")
BldCount = int(arcpy.GetCount_management(bldlyr).getOutput(0))      
      
dsc = arcpy.Describe(BldSelection)       
selection_set = dsc.FIDSet               
if len(selection_set) == 0:             
    print "There are no features selected"        
                   
elif BldCount >= 1:      
    #Gets the highest AddressID and calculates new point to assign new highest AddressID      
    Bld_list = []            
    with arcpy.da.SearchCursor(bldlyr, ["Bld_ID"]) as cursor:            
        for row in cursor:    
            try:            
                if "Bld" in row[0]:    
                        
                    Bld_list.append(int(row[0].strip("Bld")))               
            except TypeError:            
                pass                    
    del cursor            
    
    print Bld_list    
            
    Bld_list.sort()            
    Bld_ID = Bld_list[-1] + 1            
          
      
    with arcpy.da.UpdateCursor(BldSelection, "Bld_ID") as rows:             
        for row in rows:                
            row[0] = 'Bld' + str(Bld_ID)    
            Bld_ID += 1                        
            rows.updateRow(row)        
        del row             
        del rows

Re: If-then-else

CCWeedcontrol — Sun, 12 Dec 2021 06:47:50 GMT

Wes suggestion is interesting, i never thought of doing that. I made the change to the code but the Bld_ID for the selected feature doesn't get populated.

I will still like to see how to use the if-ten-else

import arcpy, os  
from arcpy import env  
arcpy.env.workspace = r"Database Servers\DSD15_SQLEXPRESS.gds\CCAPTEST (VERSION:dbo.DEFAULT)"  
  
arcpy.env.qualifiedFieldNames = False          
arcpy.env.overwriteOutput = True    
  
BldSelection = "CCAPTEST.DBO.BldTaxChar"           
Bld = arcpy.env.workspace + os.sep + "CCAPTEST.DBO.BldTaxChar" #target point feature class

    
bldlyr = arcpy.MakeFeatureLayer_management(Bld,"Building_layer","AddressID > ''")  
BldCount = int(arcpy.GetCount_management(bldlyr).getOutput(0))
   
    
dsc = arcpy.Describe(BldSelection)     
selection_set = dsc.FIDSet

if len(selection_set) == 0:           
    print "There are no features selected"        
                 
elif BldCount >= 1:


    # Start an edit session. Must provide the worksapce.
    edit = arcpy.da.Editor(arcpy.env.workspace)

    # Edit session is started without an undo/redo stack for versioned data
    #  (for second argument, use False for unversioned data)
    edit.startEditing(True)

    # Start an edit operation
    edit.startOperation()
    
    #Gets the highest AddressID and calculates new point to assign new highest AddressID    
    Bld_list = []          
    with arcpy.da.SearchCursor(bldlyr, ["Bld_ID"]) as cursor:          
        for row in cursor:  
            try:          
                if "Bld" in row[0]:  
                      
                    Bld_list.append(int(row[0].strip("Bld")))             
            except TypeError:          
                pass                  
    del cursor          
  
    print Bld_list  
          
    Bld_list.sort()          
    Bld_ID = Bld_list[-1] + 1          
        
    
    with arcpy.da.UpdateCursor(BldSelection, "Bld_ID") as rows:           
        for row in rows:              
            row[0] = 'Bld%05d' %Bld_ID 
            Bld_ID += 1                      
            rows.updateRow(row)      
        del row           
        del rows
    # Stop the edit operation.
    edit.stopOperation()

    # Stop the edit session and save the changes
    #edit.stopEditing(True)
    if arcpy.Exists(parcel_lyr): arcpy.Delete_management(parcel_lyr)
    arcpy.RefreshActiveView()

Re: If-then-else

WesMiller — Sun, 12 Dec 2021 06:47:53 GMT

See below

condition = 1
if condition == 1:
    print 'yes it is'
else:
    print "no it isn't"

Edit

This may be a better example for what you are trying to do.

import arcpy
fc = 'Your feature class'
field = 'your field'
with arcpy.da.SearchCursor(fc, [field]) as cursor:
    for row in cursor:
        if row[0] >'':
            print row[0]
        else:
            print 'update row'

Re: If-then-else

CCWeedcontrol — Sun, 12 Dec 2021 06:47:56 GMT

ok, for some reason i was thinking i had to put an if-then-else statement after "elif BldCount >= 1: " line 21

after making the following adjustment, the selected features "Bld_ID" field still doesn't populate when i run the following code...? I get no error.

Edit:

I had things that i need to change. the code is now working, i think. i will do testing.

Thanks Wes!

import arcpy, os  
from arcpy import env  
arcpy.env.workspace = r"Database Servers\DSD15_SQLEXPRESS.gds\CCAPTEST (VERSION:dbo.DEFAULT)"  
  
arcpy.env.qualifiedFieldNames = False          
arcpy.env.overwriteOutput = True    
  
BldSelection = "CCAPTEST.DBO.BldTaxChar"           
Bld = arcpy.env.workspace + os.sep + "CCAPTEST.DBO.BldTaxChar" #target point feature class

BldCount = int(arcpy.GetCount_management(Bld).getOutput(0))

dsc = arcpy.Describe(BldSelection)     
selection_set = dsc.FIDSet

if len(selection_set) == 0:           
    print "There are no features selected"        
                 
elif BldCount >= 1:


    # Start an edit session. Must provide the worksapce.
    edit = arcpy.da.Editor(arcpy.env.workspace)

    # Edit session is started without an undo/redo stack for versioned data
    #  (for second argument, use False for unversioned data)
    edit.startEditing(True)

    # Start an edit operation
    edit.startOperation()
    
    #Gets the highest AddressID and calculates new point to assign new highest AddressID    

    with arcpy.da.SearchCursor(BldSelection , "Bld_ID") as cursor:  
        for row in cursor:  
            if row[0] >'':  
    
                Bld_list = []          
                with arcpy.da.SearchCursor(Bld, ["Bld_ID"]) as cursor:          
                    for row in cursor:  
                        try:          
                            if "Bld" in row[0]:  
                                  
                                Bld_list.append(int(row[0].strip("Bld")))             
                        except TypeError:          
                            pass                  
                del cursor          
              
                print Bld_list  
                      
                Bld_list.sort()          
                Bld_ID = Bld_list[-1] + 1          
                    
                
                with arcpy.da.UpdateCursor(BldSelection, "Bld_ID") as rows:           
                    for row in rows:              
                        row[0] = 'Bld%05d' %Bld_ID 
                        Bld_ID += 1                      
                        rows.updateRow(row)      
                    del row           
                    del rows

            else: #other process sptial join
        
                edit.stopOperation()
    # Stop the edit operation.
    # Stop the edit session and save the changes
    #edit.stopEditing(True)
    #if arcpy.Exists(parcel_lyr): arcpy.Delete_management(parcel_lyr)
    arcpy.RefreshActiveView()

Re: If-then-else

CCWeedcontrol — Fri, 08 Jan 2016 19:41:53 GMT

spoke to soon the code is not working, no errors, field Bld_ID doesn't get populated

Re: If-then-else

CCWeedcontrol — Fri, 08 Jan 2016 19:52:38 GMT

I just noticed that some of the selected features are "NULL", would that affect line 36?

Re: If-then-else

WesMiller — Fri, 08 Jan 2016 20:01:12 GMT

Null < ''

Re: If-then-else

CCWeedcontrol — Sun, 12 Dec 2021 06:47:58 GMT

I have tried the following for blank and null attributes for line 36, but i am getting error. Parsing error SyntaxError: invalid syntax

with arcpy.da.SearchCursor(BldSelection , "Bld_ID") as cursor:  
        for row in cursor:  
            if row[0] > '' or row[0] Null <":

and

with arcpy.da.SearchCursor(BldSelection , "Bld_ID") as cursor:  
        for row in cursor:  
            if row[0] > '' :
               if row[0] Null <":

I have tried, but nothing happends, the Bld_ID of the selected feature doesn't update.

 with arcpy.da.SearchCursor(BldSelection , "Bld_ID") as cursor:  
        for row in cursor:  
            if row[0] > None or row[0] == ' ':

Re: If-then-else

DanPatterson_Retired — Sun, 12 Dec 2021 06:48:01 GMT

You need to learn something about nothing...

nothing = None, "", {}, []

obj = None  # or "" '' [] et
if not obj:
    print("something here")
else:
    print("nothing object")

Re: If-then-else

CCWeedcontrol — Sun, 12 Dec 2021 06:48:04 GMT

I have tried the following but nothing happens, no error

obj = None, "", ' '
    with arcpy.da.SearchCursor(BldSelection , "Bld_ID") as cursor:  
        for row in cursor:  
            if not obj:
                    Bld_list = []          
                    with arcpy.da.SearchCursor(Bld, ["Bld_ID"]) as cursor:          
                        for row in cursor:  
                            try:          
                                if "Bld" in row[0]:  
                                      
                                    Bld_list.append(int(row[0].strip("Bld")))             
                            except TypeError:          
                                pass                  
                    del cursor     
                     print Bld_list  
                          
                    Bld_list.sort()          
                    Bld_ID = Bld_list[-1] + 1          
                        
                    
                    with arcpy.da.UpdateCursor(BldSelection, "Bld_ID") as rows:           
                        for row in rows:              
                            row[0] = 'Bld%05d' %Bld_ID 
                            Bld_ID += 1                      
                            rows.updateRow(row)      
                        del row           
                        del rows

            else: #other process sptial join
                # Stop the edit operation.
                edit.stopOperation()

Re: If-then-else

DanPatterson_Retired — Fri, 08 Jan 2016 22:41:12 GMT

Ok... clearly

obj is an object... any object ... pick one

it will either have a null state, such as empty strings ( '', ""), lists dictionaries or sets ( [], {} () ) or...
it will be null, like None, np.Nan etc etc

if obj:

means if the object is something or has a non-null values or state.... do something in the lines that immediately follow
conclusion? if the value is something then do something with it

if not obj:

if the object is null, then do something. this condition is used to do "stuff" when objects are null

Confused????? Never check the code you are trying to get working to see if the logic works... you will just keep spinning your cerebral wheels. always check the logic you are working on, using something that you know works.

Re: If-then-else

CCWeedcontrol — Sun, 10 Jan 2016 17:18:38 GMT

Dan I uderstad what you and Wes are saying with the explanations/logic I am just not sure how to put it into the current code to reflect what I am trying to accomplish.

Re: If-then-else

DanPatterson_Retired — Sun, 10 Jan 2016 19:18:44 GMT

I have lost sight of...or not fully grasped... the need for the code in the first place. This appears to be a solution to a one-off or seldom performed task. I advise breaking it into parts that you can solve even if it means that you will have to perform several individual steps rather than one automagic solution.

Re: If-then-else

WesMiller — Sun, 10 Jan 2016 20:53:03 GMT

In support of what Dan is saying it appears to be a simple select by attribute followed by a field calculate. The whole process shouldn't take more than a minute.