Python to batch generate QR codes

Posted by in Data, Design, Labeling

This is an overview of a script I developed utilizing python urllib, google’s chart api, and NOAA’s live stream monitoring charts. I created this proof of concept for a paper map that includes some graphic labels for stream monitoring stations, including a QR code that can be scanned to bring up the live chart for the stream gauge. Here’s the map as a proof of concept (the QR’s in the map below are dummy, so they won’t really take you anywhere, real one’s to follow).

Capture

Here’s the VNCC1 QR code:

vncc1

Screenshot using google goggles for the QR Capture:

Screenshot_2016-03-24-13-13-22

The cart for VNCC1 right now (3/24/2016 6:44am):

VNCC1

And a screen shot after hitting the link in goggles:

Screenshot_2016-03-24-13-13-42

This proof of concept was well received and we are going to utilize the labels in a variety of ways for a big mapbook project.

As a preemptive measure, I went ahead and developed a way to generate the labels for each station in California. The first part of this is to obtain/download the QR code for each gauge. First thing I did was to grab the national shapefile of the monitoring stations at NOAA.

This shapefile happens to have the URL for each monitoring station hydrograph.

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First thing to notice is that the URL is consistent up to the point “wfo=…” I did a little testing and I know that the “wfo=mtr&” portion can just be removed, so a valid URL for any given gauge hydrograph is (plus a shorter URL is better for QR codes):

http://water.weather.gov/ahps2/hydrograph.php?gage=

…with the gauge ID on the end. For instance hit, http://water.weather.gov/ahps2/hydrograph.php?gage=vncc1

Next step is to select the California gauges and copy the table from the shapefile into excel and build the corrected URLs. Next, I perform a spatial selection of gauge points within the bounds of California, then right click to the left of one of the selected points in the attribute table and hit Copy Selected.

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Then paste into excel and delete all columns except the ‘URL’ field.

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Now, calculate a simplified URL into column B with the formula, in cell B2:

=”http://water.weather.gov/ahps2/hydrograph.php?gage=”&RIGHT(A2,5)

Copy the formula down the whole column (with B2 highlighted, double-click the little green box in the lower right corner), then hit ctrl+c to copy all URLs…

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..and paste them into a text editor (I use notepad++).

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Now save this as a text file, mine is here, C:\Users\brian\Desktop\QRs\00 urls.txt.

Next is the python, commented below.

import urllib
import os
 
#this is the google chart api url to create a 300x300 px QR code of the url after chl=
pre = "https://chart.googleapis.com/chart?chs=300x300&cht=qr&chl="
 
#text file with all the URLs
text=r"C:\Users\brian\Desktop\QRs\00 urls.txt"
 
#directory i want my QR code image to go
dir=r"C:\Users\brian\Desktop\QRs"
 
#make the directory above if it's not there
if not os.path.exists(dir):
    os.makedirs(dir)
 
#opens the address list text file (from the 'text' variable defined above) in read mode ("r")
with open(text,"r") as text_file:
  #creates a list of lines from the text file 'text'
  lines = [line.rstrip('\n') for line in open(text)]
  #loops each line
  for URL in lines:
    #concatenates the URL for the QR code and the google chart API url
    image = pre + URL
    #name for the QR code image text right of = in url, will be the station ID 
    name = URL.split('=')[-1]
    #creates the output file name for the QR .png image with the dir and name
    filename = os.path.join(dir,name+".png")
    #try to download the image and save it to the path else skip
    try:
      urllib.urlretrieve(image, filename)
    except KeyboardInterrupt:
      break
    except:
      print "Timed-out or got some other exception: "+image

Now, save that python script in the same spot as the text file, double-click it, and watch some magic. My next step is to extend the table a little bit and run it through InDesign data merge to auto generate the label boxes for each gauge station.

Boom,whole bunch of QR codes and a reusable script/system.

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