Sort a polygon feature class spatially using Python

I was manually adjusting a custom grid for a map series this morning, a task which I have not had to do for several years now, when the time came to export the maps. By this point, my grid numbers were completely messed up because of all the shifting and reshaping I had to do.

It would make sense to number the grid from left to right, top to bottom. However, the ability to spatially sort a feature class in ArcGIS is hidden behind an Advanced Licence in the Sort tool.

License: For the Field(s) parameter, sorting by the Shape field or by multiple fields is only available with an Desktop Advanced license. Sorting by any single attribute field (excluding Shape) is available at all license levels.

I had this prickly feeling in the back of my head that I had found a workaround for this before. I went searching through the blog (since I have posted about things twice because I forgot about the first post), but I didn’t find it.

Undeterred, I searched through my gists (unrelated note – why does using the “user:<username> <search term> ” trick in the GitHub search bar now flag as spam?!) and I found it!

Link for mobile users is here.

I’m pretty sure there is a much better way to do this, but I need this so rarely that I don’t see the need to rewrite it. It also would work much better as a function. It takes a polygon feature class and sorts the selected features from left to right, top to bottom.

Description of this hastily drawn, blurry PowerPoint graphic: Chaotic, unsorted grid on the left. Slightly less chaotic, sorted grid on the right.

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Inserting spaces into CamelCase

I have some trauma related to regular expressions from my university days. Yes, they are super useful. Do I enjoy using them? Does anyone?

Image result for regular expressions meme

I routinely modify and create new instances of the AMIS GIS data model. Depending on the client and the type of assets they have, there can be 4 feature datasets, containing about 5 feature classes each, or 9 feature datasets with up to 50 feature classes spread across the database.

Inevitably at some point in the process of losing my mind, I will forget that the alias is lost when creating a new feature class, or randomly copying it over or whatever. I then end up with dozens of feature classes with really ugly looking abbreviated layer names in CamelCase. So for posterity, and so that I will never ever forget this ridiculously easy thing again:

One thing I’ve omitted from the script is that I usually store the feature class names with a prefix, e.g. fc_name = wps_WaterPumpStation. In this case, I would use split on the feature class name before passing it to the alterFCAlias function i.e. fc_name.split("_")[1].

Link for mobile users is here.

Aaaaaaand I’ve just realised that I’ve forgotten this basic task so many times over the last few years that I actually already have a blog post about it, except for some reason I was updating the layer names in ArcMap every time instead of resetting it once on the feature classes themselves.

Image result for what were you thinking meme

Convert a list of field names and aliases from Excel to table using ArcPy

I went digging through my old workspace and started looking at some of my old scripts. My style of coding back then is almost embarrassing now 🙂 but that’s just the process of learning. I decided to post this script I wrote just before ArcGIS released their Excel toolset in 10.2.

From what I can recall, I needed to create a file geodatabase table to store records of microbial sample data. Many of the field names were the chemical compound themselves, such as phosporus or nitrogen, or bacterial names. For brevity’s sake, I had to use the shortest field names possible while still retaining the full meaning.

I set up a spreadsheet containing the full list of field names in column FIELD_NAMES and their aliases in ALIAS. I created an empty table in a file gdb, and used a SearchCursor on the spreadsheet to create the fields and fill in their aliases.

This solution worked for me at the time, but of course there are now better ways to do this.

Add a new field to a feature class using NumPy

I needed to add a field to dozens of layers. Some of the layers contained the field already, some of them contained a similar field, and some of them did not have the field. I did not want to batch Add Field, because not only would it fail on the layers which already had the field, but it is super slow and I would then still have to transfer the existing values from the old field to the new field.

I wrote the tool in the ArcMap Python window, because I found it easier to load my layers into an mxd first as they were lying all over the place. The new field to be added is set up as a NumPy array, with the relevant dtype.

The script loops over all the layers in the document, adding the field via the Extend Table tool, and then transferring the values from the old field to the new field. Deleting the old field at the end would be an appropriate step to include, but I didn’t, purely because I’ve lost data that way before.

Split line interactively using ArcPy FeatureSets

Back when I was doing a lot of GIS work for civil and electrical asset management, a common task I had was to ensure that all civil structures represented as a polyline (reticulation and bulk pipelines, eletrical feeder cables, road surfaces etc) were split at the physical road intersections as seen on the latest available aerial imagery, as well as where they crossed each other.

This task wasn’t too much trouble if the lines were already drawn across each other, as more often than not, the lines crossed at the road intersections. The result was usually achieved by using the Planarize option on the Advanced Editing toolbar. However, it became a problem for new areas which had to be digitised by hand (no CAD drawings or shapefiles received), or lines which had to be corrected.

I would have to visually check on the imagery where the road intersections were, and then manually split each polyline. I ran through some ideas, including digitising all road intersections as points (which would be good data to have anyway), and then splitting all the lines at the closest intersection by using the Split Line at Point tool.

I did however want to create a method of splitting the line multiple times on the fly, instead of just splitting it once (which is the option provided by the Split button on the Editor toolbar). I wanted to be able to select a line, click as many points along the line as I wanted, and then split the line into those points.

The tool iterates over all the points created by the user in the FeatureSet. For each point, a temporary diagonal is created to cut the original polyline. This new part is saved in a list and the tool runs again on the original polyline (minus the new part). Once all the points have been processed, the original polyline is removed from the feature class, and the new parts are inserted. All feature attributes are maintained.

My intention with this tool was to expand it with more features, fix the bugs (it would randomly not work) and upload it as a toolbox. However, the need to do that fell away. I also realised I was starting to get into a space where I was forcing as much code as I could into my work in order to get through the day.

Write feature class properties to a Word document using python-docx

It’s been too long since I’ve posted some code. A few months ago I had a requirement to basically create a UML view of a file gdb and present each feature class as tables for inclusion in a functional specification Word document.

Sadly, since the demise of ArcGIS Diagrammer, there has never been something to take its place. The actual request I received was to take screenshots of the properties dialog box of each feature class in ArcCatalog, and paste those into the document with appropriate headings.

I recognised this request for the total waste of my time it would be, and promptly set about looking for an alternative. I realised I had python-docx already installed.

For each feature class in the geodatabase, a new paragraph is started with the name of the feature class in bold. A line break is inserted, followed by a table. The name and type of each field is added as a new row into the table, and a page break is inserted to start the properties of the next feature class on a new page.

It took me about an hour to look up alternative methods and to put this script together. Most of the time was spent on getting the cells in the table to insert properly, using the age-old method of trial and error. I did it this way to save myself the pain of manually inserting screenshots, knowing that if the format of the feature classes changed I would have to do new screenshots repeatedly.