How to construct a dict from lists or numpy arrays?

Question

Can you please teach me to construct a dict from lists?

I have two lists:

A = [1, 2, 0, 0, 3]

and

B = ['HAM', 'SPAM', 'HAM', 'HAM', 'SPAM']

I want a dict like this:

Dict = [
...     {'Count': 1., 'Class': 'HAM'},
...     {'Count': 2., 'Class': 'SPAM'},
...     {'Count': 0., 'Class': 'HAM'},
...     {'Count': 0., 'Class': 'HAM'},
...     {'Count': 3., 'Class': 'SPAM'},
... ]

Which include two feature keys 'Count' and 'Class' as well...

Much appreciated! Thanks.

That's not a dictionary, that's a list of dictionaries. What have you tried so far? — jonrsharpe
– jonrsharpe, Commented Jul 10, 2014 at 20:09

redcrow · Accepted Answer · 2014-07-10 20:27:23Z

2

That's not a dict, but a list (of dictionaries). Anyway, if what you want is this:

data = [
            {'Count': 1., 'Class': 'HAM'},
            {'Count': 2., 'Class': 'SPAM'},
            {'Count': 0., 'Class': 'HAM'},
            {'Count': 0., 'Class': 'HAM'},
            {'Count': 3., 'Class': 'SPAM'}
       ]

then:

data = [{'Count': float(x[0]), 'Class': x[1]} for x in zip(A, B)]

update

I've updated my answer because I've just noticed that you required a float as value for 'Count'.

edited Jul 10, 2014 at 20:27

answered Jul 10, 2014 at 20:18

redcrow

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3 Comments

Cory Kramer Over a year ago

That's basically a copy-paste of my answer.

redcrow Over a year ago

Sorry, I didn't notice your answer before mine. I can delete mine for honesty if you want, but it wasn't a copy-paste, just the same.

Cory Kramer Over a year ago

Meh it's fine to leave it up, it show's that there's a consensus :) great minds think alike

Cory Kramer · Accepted Answer · 2014-07-10 20:15:56Z

1

>>> A = [1, 2, 0, 0, 3]
>>> B = ['HAM', 'SPAM', 'HAM', 'HAM', 'SPAM']

>>> zip(A,B)
[(1, 'HAM'), (2, 'SPAM'), (0, 'HAM'), (0, 'HAM'), (3, 'SPAM')]

>>> [{'Count':i[0], 'Class':i[1]} for i in zip(A,B)]

Output

[{'Count': 1, 'Class': 'HAM'},
 {'Count': 2, 'Class': 'SPAM'},
 {'Count': 0, 'Class': 'HAM'},
 {'Count': 0, 'Class': 'HAM'},
 {'Count': 3, 'Class': 'SPAM'}]

answered Jul 10, 2014 at 20:15

Cory Kramer

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1 Comment

ZJS Over a year ago

Instead of using an index why not just unpack the values? for key,value in zip(A,B)

shx2 · Accepted Answer · 2014-07-10 20:23:55Z

1

Instead of a list of dicts (i.e. records), you can use pandas.

pandas is perfect for representing this kind of data.

df = pd.DataFrame({ 'Count': A, 'Class': B})
df
=> 
  Class  Count
0   HAM      1
1  SPAM      2
2   HAM      0
3   HAM      0
4  SPAM      3

[5 rows x 2 columns]

df.Class
=>
0     HAM
1    SPAM
2     HAM
3     HAM
4    SPAM
Name: Class, dtype: object

df.Class[1]
=> 'SPAM'

df.ix[1]
=>
Class    SPAM
Count       2
Name: 1, dtype: object

df.ix[1].Class
=> 'SPAM'

answered Jul 10, 2014 at 20:23

shx2

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Comments

famousgarkin · Accepted Answer · 2014-07-10 20:37:47Z

1

The Dict = [{}, {}, ...] construct you have there is not a dict but a list ([]) of dicts ({}).

To get the required result using zip and list comprehension:

>>> A = [1, 2, 0, 0, 3]
>>> B = ['HAM', 'SPAM', 'HAM', 'HAM', 'SPAM']

>>> [{'Count': a, 'Class': b} for a, b in zip(A, B)]
[{'Count': 1, 'Class': 'HAM'},
 {'Count': 2, 'Class': 'SPAM'},
 {'Count': 0, 'Class': 'HAM'},
 {'Count': 0, 'Class': 'HAM'},
 {'Count': 3, 'Class': 'SPAM'}]

edited Jul 10, 2014 at 20:37

answered Jul 10, 2014 at 20:23

famousgarkin

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2 Comments

redcrow Over a year ago

Values of the Count key should be numbers.

famousgarkin Over a year ago

@f_ficarola You are right, got confused by the . and the syntax coloring. Fixed, almost the same as others now. Still laving it here for the zip expansion.

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