I have three columns (other than OID FID) in my shapefiles for river. And I want to update "from node" and "to node column" Before update from node to node gridcode 2 3 8 3 2 9 7 2 5 After update, I want "node column" to be same as "grid code" column, so I used field calculator in ArcGIS (from node = gridcode). My "from node" column has been changed to gridcode but not sure how to update "to node" column (that depends on values in “from node” column) Below is the final result I want: from node to node gridcode 8 9 8 9 8 9 5 8 5 Half of the code is working import arcpy , os , sys from arcpy import env fc = r "C:/Users/wis/Desktop/python/fe/fea_c.shp" # instantiate empty dictionary #'FROM_NODE','GRID_CODE','TO_NODE' name of columns in my attribute table node_values = {} # build dictionary of values with arcpy . da . SearchCursor ( fc , [ 'FROM_NODE' , 'GRID_CODE' ]) as cursor : for row in cursor : old_node = row [ 0 ] new_node = row [ 1 ] node_values [ FROM_NODE ] = new_node with arcpy . da . UpdateCursor ( fc , [ 'FROM_NODE' , 'TO_NODE' , 'GRID_CODE' ]) as cursor : for row in cursor : # set fromnode to gridcode value row [ 0 ] = row [ 2 ] # set tonode to new equivalent node to_node = row [ 1 ] # I get an error here new_to_node = node_values [ TO_NODE ] row [ 1 ] = new_to_node cursor . updateRow ( row) The error is because row[1] or "to node" does not have all numbers that are in "from node" or "grid code" Because some values will repeat in t"no node" because one river can be connected to more than one rivers. However no repetition in "gridcode" and "from node" Any suggestions fe.zip

Mr. Ammaratalib! I am having the same issue here. can you share with me the python code as to how you could achieve your target! Will appreciate it a lot as I am newly learning python.

nav[aria-label="Primary Navigation"] { padding: 0; & ul { list-style: none; width: 100%; display: flex; flex-direction: row; justify-content: start; align-items: start; gap: 30px; padding: 0; & li { margin: 0; } & ul li { list-style: none; } } }

Update values in attribute table

ammaratalib

I have three columns (other than OID FID) in my shapefiles for river. And I want to update "from node" and "to node column"

Before update

from node&nbsp;&nbsp;&nbsp; to node&nbsp;&nbsp;&nbsp; gridcode&nbsp;&nbsp;&nbsp;
 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8
 3&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 9
 7&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 2&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5

After update, I want "node column" to be same as "grid code" column, so I used field calculator in ArcGIS (from node = gridcode). My "from node" column has been changed to gridcode but not sure how to update "to node" column (that depends on values in “from node” column)

Below is the final result I want:

from node&nbsp;&nbsp;&nbsp; to node&nbsp;&nbsp;&nbsp; gridcode 
8&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 9&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8 
9&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 9 
5&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 8&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 5

<SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;node_values </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">{}</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;
 </SPAN><SPAN class="" style="color: #858c93; border: 0px; font-weight: inherit; font-size: inherit;"># build dictionary of values</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;
 </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">with</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> arcpy</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">.</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">da</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">.</SPAN><SPAN class="" style="color: #2b91af; border: 0px; font-weight: inherit; font-size: inherit;">SearchCursor</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">(</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">fc</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">,</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">'FROM_NODE'</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">,</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">'GRID_CODE'</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">])</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">as</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> cursor</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">:
</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;</SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">for</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> row </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">in</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> cursor</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">:
</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;old_node </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> row</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">0</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]
</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; new_node</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> row</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">1</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; node_values</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">FROM_NODE</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> new_node&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
</SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">with</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> arcpy</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">.</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">da</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">.</SPAN><SPAN class="" style="color: #2b91af; border: 0px; font-weight: inherit; font-size: inherit;">UpdateCursor</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">(</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">fc</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">,</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">'FROM_NODE'</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">,</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">'TO_NODE'</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">,</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">'GRID_CODE'</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">])</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">as</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> cursor</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">:</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
</SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp; for</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> row </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit;">in</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> cursor</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">:</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </SPAN><SPAN class="" style="color: #858c93; border: 0px; font-weight: inherit; font-size: inherit;"># set fromnode to gridcode value</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; row</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">0</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> row</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">2</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; </SPAN><SPAN class="" style="color: #858c93; border: 0px; font-weight: inherit; font-size: inherit;"># set tonode to new equivalent node</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; to_node </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> row</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">1</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"></SPAN><SPAN class="" style="color: #858c93; border: 0px; font-weight: inherit; font-size: inherit;"># I get an error here</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; new_to_node </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> node_values</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">TO_NODE</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; row</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">[</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit;">1</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">]</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> new_to_node&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cursor</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">.</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">updateRow</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">(</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">row)</SPAN><CODE><SPAN class="" style="color: #2b91af; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">Half</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"> of the code </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">is</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"> working&nbsp;&nbsp;
</SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">import</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"> arcpy</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">,</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"> os</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">,</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"> sys&nbsp;&nbsp;&nbsp;&nbsp;
 </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">from</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"> arcpy </SPAN><SPAN class="" style="color: #101094; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">import</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"> env&nbsp;&nbsp;&nbsp;&nbsp;
 fc</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">r</SPAN><SPAN class="" style="color: #7d2727; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">"C:/Users/wis/Desktop/python/fe/fea_c.shp"</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">&nbsp;&nbsp;&nbsp; 
</SPAN><SPAN class="" style="color: #858c93; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;"># instantiate empty dictionary</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">&nbsp;&nbsp;&nbsp; 
</SPAN><SPAN class="" style="color: #858c93; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">#'FROM_NODE','GRID_CODE','TO_NODE' name of columns in my attribute table</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit; margin: 0px;">&nbsp;&nbsp;&nbsp;&nbsp;
</SPAN>

The error is because row[1] or "to node" does not have all numbers that are in "from node" or "grid code" Because some values will repeat in t"no node" because one river can be connected to more than one rivers. However no repetition in "gridcode" and "from node" Any suggestions

fe.zip

Find more posts tagged with

Accepted answers

All comments

ammaratalib

Thanks Xander. It makes sense now. I will use this code to make changes in my subbasin shape files too.

ammaratalib

yes it is working now. Thanks Dan. I appreciate that.

ammaratalib

# on line 10 before equal sign there should be "no_" instead of "tonode" (typo i guess)
because you have not defined tonode.

#if i make that change code does not produce the result that line 16 is showing
when i run your code i got
is_good
array([2, 2, 3, 4, 5, 2, 2, 3, 6, 4, 5,7])

looks like your code is setting values in "is_good" equal to the last value of "to_" when "to_=from_" or when "to_" is equal to any value "in from_"
if to_!=from_ then no change in values of "is_good"
#That is replacemnet rather than updating values (if on line 10 it's "no_" rather than tonode)
I guessing wording for my question was very confusing to begin with.
But I liked practicing on your code for my own understanding :-). It helped me to understand about replacement
Now going to practice on arcpy:-)

DanPatterson_Retired

can you check my logic so I can see if I can produce a vectorized solution using an arcpy.da.ExtendTable operation ...

EDITED to fix the reference to fix_me array

fix_me <SPAN class="operator token">=</SPAN> np<SPAN class="punctuation token">.</SPAN>array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">6</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">7</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>
is_good <SPAN class="operator token">=</SPAN> np<SPAN class="punctuation token">.</SPAN>copy<SPAN class="punctuation token">(</SPAN>fix_me<SPAN class="punctuation token">)</SPAN>
from_ <SPAN class="operator token">=</SPAN> np<SPAN class="punctuation token">.</SPAN>array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>
to_ <SPAN class="operator token">=</SPAN> np<SPAN class="punctuation token">.</SPAN>array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="keyword token">for</SPAN> i <SPAN class="keyword token">in</SPAN> range<SPAN class="punctuation token">(</SPAN>len<SPAN class="punctuation token">(</SPAN>from_<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; is_good<SPAN class="punctuation token">[</SPAN>np<SPAN class="punctuation token">.</SPAN>where<SPAN class="punctuation token">(</SPAN>fix_me <SPAN class="operator token">==</SPAN> from_<SPAN class="punctuation token">[</SPAN>i<SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">]</SPAN> <SPAN class="operator token">=</SPAN> to_<SPAN class="punctuation token">[</SPAN>i<SPAN class="punctuation token">]</SPAN>

<SPAN class="comment token"># ---- compare the results, old and new ----</SPAN>

fix_me
array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">6</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">7</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN>
i
s_good
array<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">[</SPAN><SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">3</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">2</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">6</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">7</SPAN><SPAN class="punctuation token">]</SPAN>
<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

can you check my logic so I can see if I can produce a vectorized solution

XanderBakker

I just ran the code below:

<SPAN class="keyword token">def</SPAN> <SPAN class="token function">main</SPAN><SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">import</SPAN> arcpy

&nbsp;&nbsp;&nbsp; fc <SPAN class="operator token">=</SPAN> r<SPAN class="string token">'C:\GeoNet\UpdateNodes\shp\fea_c.shp'</SPAN>

&nbsp;&nbsp;&nbsp; node_values <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">{</SPAN>r<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">:</SPAN> r<SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN> <SPAN class="keyword token">for</SPAN> r <SPAN class="keyword token">in</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>SearchCursor<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'FROM_NODE'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">'GRID_CODE'</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">}</SPAN>

&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>UpdateCursor<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'FROM_NODE'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">'TO_NODE'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">'GRID_CODE'</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN> <SPAN class="operator token">=</SPAN> row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">]</SPAN>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token"># set tonode to new equivalent node</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; to_node <SPAN class="operator token">=</SPAN> row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="comment token"># I get an error here</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">if</SPAN> to_node <SPAN class="keyword token">in</SPAN> node_values<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; new_to_node <SPAN class="operator token">=</SPAN> node_values<SPAN class="punctuation token">[</SPAN>to_node<SPAN class="punctuation token">]</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN> <SPAN class="operator token">=</SPAN> new_to_node
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">else</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">print</SPAN> to_node<SPAN class="punctuation token">,</SPAN> <SPAN class="string token">" not in dictionary"</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; cursor<SPAN class="punctuation token">.</SPAN>updateRow<SPAN class="punctuation token">(</SPAN>row<SPAN class="punctuation token">)</SPAN>


<SPAN class="keyword token">if</SPAN> __name__ <SPAN class="operator token">==</SPAN> <SPAN class="string token">'__main__'</SPAN><SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; main<SPAN class="punctuation token">(</SPAN><SPAN class="punctuation token">)</SPAN><SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

and it updated, but there are as you mentioned some case that do not have value in the dictionary:

2 not in dictionary
24 not in dictionary
36 not in dictionary
41 not in dictionary

ammaratalib

>>> node_values My dictionary. for first part (search cursor)

{1: 1, 3: 2, 4: 5, 5: 3, 6: 4, 7: 6, 8: 8, 9: 7, 10: 12, 11: 9, 12: 10, 13: 11, 14: 13, 15: 14, 16: 19, 17: 24, 18: 15, 19: 16, 20: 17, 21: 18, 22: 20, 23: 21, 25: 22, 26: 23, 27: 26, 28: 29, 29: 25, 30: 27, 31: 33, 32: 28, 33: 32, 34: 30, 35: 31, 37: 35, 38: 34, 39: 37, 40: 36, 42: 38, 43: 39, 44: 40}

yes the code for search cursor part is correct. I matched it with attribute table(in attached shaped file).because i am updating my "from code" based on "grid code". Next step is to update "to node" but i am getting error there (update cursor part), because to_node does not have all values that "from node" has and that's how it should be. code should not care about matching it should just update "to node".

ammaratalib

"to_node" depends on "from node".I just want to update "to_node". if i change "from node " lets say from node =3 has been changed to 2 then all 3's in "to node" should also changed to 2. Yes the reason I am getting error is because some values in "to_node" are occurring twice, because tributaries can drain into more than one river/streams. Repitition is ok. As long as values are being updated.But no repetition in "grid code" and "from node"

MitchHolley1

I think you're building your dictionary incorrectly. Right now, it's setting the key "FROM_NODE" to the variable new_node which is row[1].

Should it be something like this?

node_values <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">{</SPAN><SPAN class="punctuation token">}</SPAN> 
<SPAN class="keyword token">with</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>da<SPAN class="punctuation token">.</SPAN>SearchCursor<SPAN class="punctuation token">(</SPAN>fc<SPAN class="punctuation token">,</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">'FROM_NODE'</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="string token">'GRID_CODE'</SPAN><SPAN class="punctuation token">]</SPAN><SPAN class="punctuation token">)</SPAN> <SPAN class="keyword token">as</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp; <SPAN class="keyword token">for</SPAN> row <SPAN class="keyword token">in</SPAN> cursor<SPAN class="punctuation token">:</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; old_node <SPAN class="operator token">=</SPAN> row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">0</SPAN><SPAN class="punctuation token">]</SPAN>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; new_node<SPAN class="operator token">=</SPAN> row<SPAN class="punctuation token">[</SPAN><SPAN class="number token">1</SPAN><SPAN class="punctuation token">]</SPAN>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; 
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; node_values<SPAN class="punctuation token">[</SPAN>old_node<SPAN class="punctuation token">]</SPAN> <SPAN class="operator token">=</SPAN> new_node&nbsp; <SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

If not, print your dictionary so we can see the contents.

TedKowal

Sorry I got lost in the Nodes when reading your question!

Is there a value for the to_node you are trying to match? With the sample data you gave new_to_node = node_values[1] would fail or error because there is no lookup for it?

Do you have a default grid code for the missing node values.... if you do you could do a node_values.get(to_node,mydefaultvalue)

There is a lot of good stuff here when you have a key with no value.... Initializing a dictionary in python with a key value and no corresponding values - Stack Overflow

ammaratalib

yes that's what i did in the above code.

<SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">node_values </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">=</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;"> </SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">{}</SPAN><SPAN class="" style="color: #303336; border: 0px; font-weight: inherit; font-size: inherit;">&nbsp; is dictionary but code gets an error when I try to change no node. It works fine for grid code and from node.</SPAN>

TedKowal

What about using a dictionary to convert you node data to the grid number?

<SPAN class="comment token"># dictionary mapping {From_Node : GridCode]</SPAN>
conv <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">{</SPAN><SPAN class="number token">2</SPAN><SPAN class="punctuation token">:</SPAN><SPAN class="number token">8</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">3</SPAN><SPAN class="punctuation token">:</SPAN><SPAN class="number token">9</SPAN><SPAN class="punctuation token">,</SPAN><SPAN class="number token">7</SPAN><SPAN class="punctuation token">:</SPAN><SPAN class="number token">5</SPAN><SPAN class="punctuation token">}</SPAN>
<SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN>
New_From_Node<SPAN class="operator token">=</SPAN>conv<SPAN class="punctuation token">[</SPAN>From_Node<SPAN class="punctuation token">]</SPAN>
New_To_Node<SPAN class="operator token">=</SPAN>conv<SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">[</SPAN>To_Node<SPAN class="punctuation token">]</SPAN>
<SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN><SPAN class="punctuation token">.</SPAN>‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

You can even programically build your dictionary

ammaratalib

Dan Patterson‌ i attached shapefile. You can familiar with watershed delineation so i guess i can give you some background why am i am doing this. I used swat model to delineate my watershed but because of low elevation, I am getting unwanted streams too (i tried burning original streams, arc hydro and different threshold value).Still I need to make some changes that involve removing some sub basins/streams , merging others. Because swat does not except any subbasin that does not have any stream draining into it. So if i remove unwated streams, i need to merge some subbasins. When i remove some streams it means that gridcode and from node will not be in consecutive order. Since swat model only accept watershed and streams that have consecutive gridcode for streams. So If I change gridcode, then it will also change from node and to node connection for streams. Long story 🙂 so i am trying to use arcpy to update my from node and to node when i change gridcode.

gridcode should be same as from node and then no node will also change accordingly

DanPatterson_Retired

perhaps you could post or show a full example of the data you are working with since only portions of your example make sense

Join the Conversation

Signed in members can post, follow updates, and more. New here? Register a free account.

Quick Links

Community Help
Find useful guides, FAQs, and documents to help you navigate and make the most of Esri Community.