Question 226265 in Json Question posted in
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Working around JSON null values in Python

I have a json file where null means no value. I am trying to read from another field when the first value I am looking for is found to be null. But for the life of me I cannot figure out the syntax to achieve my goal.

>import json
>import urllib.request,urllib.parse,urllib.error        
>f h=urllib.request.urlopen('http://mrdata.usgs.gov/geology/state/json/IAXs;0')
>info=json.load(fh)
>if info['age'][0][min_epoch'] == None:
>    GEO_AGE = info['age'][0]['cmax_age']
>else:
>    GEO_AGE = info['age'][0]['min_epoch']
>print('AGE: ', GEO_AGE)

When this prints the result is:
AGE: Paleoproterozoic

This result is correct but for a reason I cannot explain…
The ‘cmax_age’ string for when the ‘min_epoch’ is null or empty is, indeed, ‘Paleoproterozoic’

However when I substitute the following:
fh = urllib.request.urlopen(‘http://mrdata.usgs.gov/geology/state/json/IACAe;0’

The result is the same
AGE: Paleoproterozoic

When, in fact, the output should be
AGE: Middle-Cambrian

`

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2

Answers


  1. 0

    When I run the code as you stated I get the expected result:

    import json
import urllib.request,urllib.parse,urllib.error
fh=urllib.request.urlopen('http://mrdata.usgs.gov/geology/state/json/IACAe;0')
info=json.load(fh)
if info['age'][0]['min_epoch'] == None:
    GEO_AGE = info['age'][0]['cmax_age']
else:
    GEO_AGE = info['age'][0]['min_epoch']
print('AGE: ', GEO_AGE)

    AGE: Middle-Cambrian

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  2. 0

    I don’t see any issues with your code and it works. Please refer below:

    import json
import urllib.request,urllib.parse,urllib.error    

fh=urllib.request.urlopen('http://mrdata.usgs.gov/geology/state/json/IAXs;0')
info=json.load(fh)
if info['age'][0]['min_epoch'] == None:
    GEO_AGE = 2 or info['age'][0]['cmax_age']
else:
    GEO_AGE = 1 or info['age'][0]['min_epoch']
print('AGE: ', GEO_AGE)

    Here is another simplified version using "or":

    import json
import urllib.request,urllib.parse,urllib.error    

def print_geo_age(url):
    fh=urllib.request.urlopen(url)
    info=json.load(fh)
    GEO_AGE = info['age'][0]['min_epoch'] or info['age'][0]['cmax_age']
    print('AGE: ', GEO_AGE)

if __name__ == "__main__":
    print_geo_age('http://mrdata.usgs.gov/geology/state/json/IAXs;0')
    print_geo_age('http://mrdata.usgs.gov/geology/state/json/IACAe;0')
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