Lab 5 [GIS5103]: Exploring and Manipulating Data


The screenshots above represent the output from a multi-part Python script that performs the following steps:
  • Step 1: Create and initialize a new geodatabase
  • Step 2: Create a Search Cursor for cities associated with county seats
  • Step 3: Create and initialize a dictionary for cities associated with county seats
The initial pseudocode for these script requirements included:

START
    Step 1:
            Setup filepath naming
    Create new geodatabase
    Iterate over features in Data:
         Copy feature from Data folder into new geodatabase
         Print name of copied feature to screen

    Step 2:
    Setup filepath naming
    Setup field list of specific attributes within cities feature (NAME, FEATURE, POP_2000)
    Use search cursor to grab a copy of specified attributes associated with cities listed as 'County Seat'
    Iterate over search cursor:
        Print attributes of each record to screen

    Step 3:
    Setup filepath naming
    Setup field list of specific attributes within cities feature (NAME, POP_2000)
    Create empty dictionary county_seats
    Use search cursor to grab a copy of specified attributes associated with cities listed as 'County Seat'
    Iterate over search cursor:
        Copy attributes to dictionary as key=NAME, value=POP_2000
    Print completed dictionary to screen
END

Key Python constructs emphasized during this week's lab included search cursors, lists, and dictionaries. The following resources were helpful for implementing these constructs:
  • Esri: Search Cursor (syntax and usage) - a key take-away from this page is the difference between arcpy.da.SearchCursor and arcpy.SearchCursor (be sure to pay attention to the parameter lists and associated data types)
  • YouTube: Python Concepts - Iterators vs Iterables - this video explains what is happening under the hood with iterators and their associated methods in for loops (use it to understand what is happening when iterating over a search cursor)




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