A basic dictionary question
Peter Otten
__peter__ at web.de
Thu Jun 11 07:28:37 EDT 2015
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?
for key in some_dict:
...
iterates over the keys of the dictionary, for (key, value) pairs you need
for key, value in some_dict.items():
...
> 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?
Have a look at collections.OrderedDict:
https://docs.python.org/dev/library/collections.html#collections.OrderedDict
If you don't care about fast access by key you can also use a list of
(key, value) pairs.
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