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Intersecting Lists Problem

AlanDodson

First post here, please be gentle...

I use ArcMap 10.3.1 and I'm having trouble with part of a Python script which will always be run from the Current mxd and active data frame.

I have to pass a list of layers to a function. I have given the script a list of all potential layers for this function (List 1). Some of those potential layers will actually be in my active data frame (always at least 1), along with other layers that are not compatible with the next function (List2). I want to only work with the potential layers that are actually present in my active data frame (List3)

I've tried the following:

import arcpy

mxd = arcpy.mapping.MapDocument("CURRENT")

df = mxd.ActiveDataFrame

List 1 = ["September", "October", "November", "December"]

List 2 = arcpy.mapping.ListLayers(df) # layers are named September and December

List 3 = list(set.(List1).intersection(List2))

The result is an empty list when it should be September, December.

I think the syntax roughly works, but the problem is that List2 returns something similar to <layer u'September'> so the two layers with identical names are not recognized as such.

(For context, I'll then be using List3 to print unique messages depending on the layer name returned... In case this helps)

Can anyone help me out?

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Accepted answers

bixb0012

This works for me:

<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> mxd <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>MapDocument<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"CURRENT"</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> df <SPAN class="operator token">=</SPAN> mxd<SPAN class="punctuation token">.</SPAN>activeDataFrame
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> 
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> List1 <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">"September"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"October"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"November"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"December"</SPAN><SPAN class="punctuation token">]</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> List2 <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN>lyr<SPAN class="punctuation token">.</SPAN>name <SPAN class="keyword token">for</SPAN> lyr <SPAN class="keyword token">in</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListLayers<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">,</SPAN> data_frame<SPAN class="operator token">=</SPAN>df<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">]</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> List3 <SPAN class="operator token">=</SPAN> list<SPAN class="punctuation token">(</SPAN>set<SPAN class="punctuation token">(</SPAN>List1<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">.</SPAN>intersection<SPAN class="punctuation token">(</SPAN>List2<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator token">></SPAN> List3
<SPAN class="punctuation token">[</SPAN>u<SPAN class="string token">'September'</SPAN><SPAN class="punctuation token">,</SPAN> u<SPAN class="string token">'December'</SPAN><SPAN class="punctuation token">]</SPAN>
<SPAN class="operator token">>></SPAN><SPAN class="operator 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>

All comments

AlanDodson

Unfortunately I'm getting an error on the line 'if lyr.name in List2:'

File "<string>" - AttributeError: 'str' object has no attribute 'name'

When I print List2 the entries are still "<layer u'September'>" or something like that so it's not matching List1 "September". My List3 result is a list of lots of duplicates of items in List2 with the "<layer u'September'>" formatting.

RandyBurton

List3 should be in the List2 (or ListLayers) order. It is likely that it would match the Table of Contents order.

AlanDodson

Ah, this looks promising. I didn't get to the layer name before but this looks like it could solve that. I will try it out first thing in the morning and report back.

Do you know if this method preserves the list order?

RandyBurton

As Pavan suggests, you need to use the layer's name property in your comparison. Try:

<SPAN class="keyword token">import</SPAN> arcpy 
mxd <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>MapDocument<SPAN class="punctuation token">(</SPAN><SPAN class="string token">"CURRENT"</SPAN><SPAN class="punctuation token">)</SPAN>
df <SPAN class="operator token">=</SPAN> mxd<SPAN class="punctuation token">.</SPAN>ActiveDataFrame

List1 <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="string token">"September"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"October"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"November"</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="string token">"December"</SPAN><SPAN class="punctuation token">]</SPAN>
List2 <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListLayers<SPAN class="punctuation token">(</SPAN>df<SPAN class="punctuation token">)</SPAN>  <SPAN class="comment token"># layers are named September and December</SPAN>
List3 <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="punctuation token">]</SPAN>

<SPAN class="keyword token">for</SPAN> lyr <SPAN class="keyword token">in</SPAN> List2<SPAN class="punctuation token">:</SPAN>
    <SPAN class="keyword token">if</SPAN> lyr<SPAN class="punctuation token">.</SPAN>name <SPAN class="keyword token">in</SPAN> List1<SPAN class="punctuation token">:</SPAN>
        List3<SPAN class="punctuation token">.</SPAN>append<SPAN class="punctuation token">(</SPAN>lyr<SPAN class="punctuation token">.</SPAN>name<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>

EDIT: As Joshua Bixby‌ shows in his code example, line 6 in my code should read as below. See: ListLayers.

<SPAN class="comment token"># ListLayers (map_document_or_layer, {wildcard}, {data_frame})</SPAN>

List2 <SPAN class="operator token">=</SPAN> arcpy<SPAN class="punctuation token">.</SPAN>mapping<SPAN class="punctuation token">.</SPAN>ListLayers<SPAN class="punctuation token">(</SPAN>mxd<SPAN class="punctuation token">,</SPAN> data_frame<SPAN class="operator token">=</SPAN>df<SPAN class="punctuation token">)</SPAN>‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍<SPAN class="line-numbers-rows"><SPAN>‍</SPAN><SPAN>‍</SPAN><SPAN>‍</SPAN></SPAN>

JoeBorgione

I found this with a google search: Python | Intersection of two lists - GeeksforGeeks

and it suggests in method 2 something close to what you are trying:

<SPAN class="keyword token">def</SPAN> <SPAN class="token function">intersection</SPAN><SPAN class="punctuation token">(</SPAN>lst1<SPAN class="punctuation token">,</SPAN> lst2<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">:</SPAN> 
    <SPAN class="keyword token">return</SPAN> list<SPAN class="punctuation token">(</SPAN>set<SPAN class="punctuation token">(</SPAN>lst1<SPAN class="punctuation token">)</SPAN> <SPAN class="operator token">&</SPAN> set<SPAN class="punctuation token">(</SPAN>lst2<SPAN class="punctuation token">)</SPAN><SPAN class="punctuation token">)</SPAN> 
  

lst1 <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">15</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">9</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">56</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">23</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">78</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">5</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">4</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">9</SPAN><SPAN class="punctuation token">]</SPAN> 
lst2 <SPAN class="operator token">=</SPAN> <SPAN class="punctuation token">[</SPAN><SPAN class="number token">9</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">36</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">47</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">26</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">10</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">45</SPAN><SPAN class="punctuation token">,</SPAN> <SPAN class="number token">87</SPAN><SPAN class="punctuation token">]</SPAN> 
<SPAN class="keyword token">print</SPAN><SPAN class="punctuation token">(</SPAN>intersection<SPAN class="punctuation token">(</SPAN>lst1<SPAN class="punctuation token">,</SPAN> lst2<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>

PavanYadav

arcpy.mapping.ListLayers(df)

is returning a list of Layer objects. Something like this:

[<map layer u'September '>, <map layer u'December'>]

How about the following:

List2a = []
for l in List2:
    List2a.append(str(l.name))

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