Re: A basic dictionary question

[MRAB]

On 2015-06-11 11:10, David Aldrich wrote:

Hi

I am fairly new to Python.  I am writing some code that uses a
dictionary to store definitions of hardware registers.  Here is a small
part of it:

import sys

register = {

     'address'  : 0x3001c,

     'fields' : {

         'FieldA' : {

             'range' : (31,20),

         },

         'FieldB' : {

             'range' : (19,16),

         },

     },

     'width' : 32

};

def main():

     fields = register['fields']

     for field, range_dir in fields:         <== This line fails

         range_dir = field['range']

         x,y = range_dir['range']

         print(x, y)

if __name__ == '__main__':

     main()

I want the code to print the range of bits of each field defined in the
dictionary.

The output is:

Traceback (most recent call last):

   File "testdir.py", line 32, in <module>

     main()

   File "testdir.py", line 26, in main

     for field, range_dir in fields:

ValueError: too many values to unpack (expected 2)

Please will someone explain what I am doing wrong?

You're iterating over the keys. What you want is to iterate over
"fields.items()" which gives the key/value pairs.

Also I would like to ask how I could print the ranges in the order they
are defined.  Should I use a different dictionary class or could I add a
field to the dictionary/list to achieve this?

Dicts are unordered. Try 'OrderedDict' from the 'collections' module.

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