Creating Spatial Data

Creating Spatial Data

GIS 5222

Jake K. Carr

Week 8

Creating Spatial Data

Jake K. Carr

Dealing with Flat Files

Sometimes the data (geographic and otherwise) we get is in a `flat' file format.

We mostly see `flat' files that come in .txt format, but .csv are `just text` files that have a comma separating values in a `row'. See Coordinates.csv.

These `separating' characters are called delimiters and there are many choices to use, such as: tabs, commas, spaces, pipes.

It is important to remember how your data is delimited when reading and writing text based data to Python.

Creating Spatial Data

Jake K. Carr

The Open Function

We can `open' files in Python with the open function.

A better way to think of it to say that Python is `reading' a text file into memory so that we can then perform some type of Python-based action onto it.

>>> myFile = open(r"C:\Users\carr .526\ Google Drive\GEOG 5222\ Lectures\Lecture 8\Data\Coordinates.csv",'r')

Here I use the argument `r' after the file path and name to tell Python that I only want to `read' the file.

Creating Spatial Data

Jake K. Carr

The readline Method

Once I have `opened' a file I can the `operate' on it using file specific methods.

The readline method does just that, it reads a line (and only one line).

>>> stHead = myFile.readline() >>> stHead 'Observation ,Name , Lat , Lon\n'

Here I create an object called stHead to which I assign the first line of the `opened' file.

Creating Spatial Data

Jake K. Carr

The readline Method

Note that a line in a flat file is the same thing as a row in an attribute table.

What is in stHead?

It's the variable names for all of the columns/fields in Coordinates.csv.

Note that stHead is a string (how do I know that?), therefore I can use some of those string manipulation methods we learned back in Lab 1.

Creating Spatial Data

Jake K. Carr

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