Module 6: Working with Geometries

For this weeks lab we were assigned to write a script that creates a TXT file and write to it the coordinates and object IDs for vertices in a shapefile. My script created a new TXT file called rivers_bat33.txt. The script I wrote writes to the txt file, point data for all vertices (0-25 features, total of 247 vertices). Each point has the following information: Feature OID, Vertex ID, X coordinate, Y coordinate, Name of the river feature.

Below are screen shots of the txt file showing all the requirements for the lab showing: Feature OID, Vertex ID, X coordinate, Y coordinate, Name of the river feature.

The flow chart for the script I created is shown below. I don't know if my nested for loop is correct as I didn't know how to correctly show the other outcome.

Notes:

•  Points, polylines, and polygons are geometry objects. Working with geometry objects and their properties by setting a cursor on shape field of a feature class. You can work with the full geometry object including all its properties such as length area, but you can also use geometry tokens (SHAPE@XY) as shortcuts to specific properties.

•  Reading geometries can be accomplished using search cursor. Specific approaches are necessary to read the properties of multipart features and polygons with holes.

•  The spatial reference can be set on cursors to work with geometries in a coordinate system that is different from that of the feature class.

Module 5 Assignment: Exploring & Manipulating Data

Module 5: Exploring and Manipulating Data

At the top of image 1 it displays that my code to create the new fGDB file was successful.

The lines after "Iterating over list" is copying the data files to the new fGDB to be used their. The next lines after that begin the cursor search to find cities that have a county seat and their population in 2000. The first 3 cities are listed in image 1 and continue to the bottom of image 3.

I currently do not have a flowchart and plan to finish the last step of lab later this week with Dr. Morgan. (Will update when I have completed.)

Notes:

-Del row needs to be under the loop.

-CreateFileGDB_management creates a new geodatabase

-Search cursors are used to search records and carry out SQL expressions.

-Update cursors are used to make changes to existing records, while insert cursors are used to add new records, delete cursors delete records.

 

 Module 4: Geoprocessing

The image above displays that my script Mod4_BTims.py is working. The first step the code does is print out the "Adding XY coordinates to the shapefile...", it adds the XY points for the hospitals shapefile. It also prints the messages out from interpreter from when the code started and finishes, using GetMessages(). 

The next line of code executes a buffer analysis on the shapefile hospitalsXYpts.shp. The buffer extends to 1000 meters around the hospitals XY coordinates and also dissolves the hospital buffers into a single-feature layer. This line of code also uses the GetMessages() to get the start and end time of the code from the interpreter.

Process Summary Notes:

-It is recommended to use arcpy.env.workspace instead of from arcpy import env followed by  env.workspace.

-arcpy.<class>.<property>

-arcpy.<toolname>_<toolboxalias>(<parameters>)

-You can use the "\n" character to add a space after each message, making messages easier to read.

Module 3 Debugging and Error Handling

This image is showing that for the first template of code I have found the two errors in the code and now the code is running. The code prints out the names of each field in the park.shp file.

This image shows the code working for the code template 2. This code had several errors and exceptions that I had to find and adjust the code. One example of the errors I encountered was that the file path that the original code had was looking for the file in the wrong file location and I had to locate where the file was in my files and correct that. This code prints out a list of layers for each data frame in the TravisCountyAustinTx.aprx.

This image shows the code running and working for the code template 3. This code we were told not to fix the errors, rather, we were supposed to use a try-except statement to trap the error and print out the error so that way the code wouldn't crash. The flowchart for how I setup the try-except statement is below to illustrate how the code would work if it encountered an exception or if there were no errors found it would print "Part A Successfully Completed". The code for template 3 prints out an error message in part A stating what the error is, part b prints the name, spatial reference, and scale for three data frames in the TravisCountyAustinTX.aprx.

Notes from this Module:

• The try-except statement is like the if statement but can be more useful working over errors and handling them.
• Error messages you receive in python can be very useful in figuring out where your code crashed, as well as, what the error type is. 
• Using the ArcGIS website to see what useful features are already in python can be used in your code or even see if the feature is spelled wrong or if a letter is case sensitive.