Python - Creating dictionary from numpy table to display lists

Question

Given the following numpy table

GR = [
    ['Student', 'Exam 1', 'Exam 2', 'Exam 3'],
    ['PersonA', '100', '90', '80'],
    ['PersonB', '88', '99', '111'],
    ['PersonC', '45', '56', '67'],
    ['PersonD', '59', '61', '67'],
    ['PersonE', '73', '79', '83'],
    ['PersonF', '89', '97', '101']
     ]

I need to create a dictionary named GL that maps names of students to lists of their exam grades. grades should be converted from str to int.

Desired Output: {'PersonA':[100, 90, 80], 'PersonB':[88, 99, 111], ect....}

Beside the point, but you're missing a closing bracket to match GR = [ — wjandrea
– wjandrea, Commented Jan 21, 2019 at 21:21

Charles Landau · Accepted Answer · 2019-01-21 21:22:14Z

1

I'm having a little trouble understanding but I think this is what you're looking for:

GL = [
    {x[0]: [int(j) for j in x[1:]]} for x in GR[1:]
]

Output:

[{'PersonA': [100, 90, 80]},
 {'PersonB': [88, 99, 111]},
 {'PersonC': [45, 56, 67]},
 {'PersonD': [59, 61, 67]},
 {'PersonE': [73, 79, 83]},
 {'PersonF': [89, 97, 101]}]

answered Jan 21, 2019 at 21:22

Charles Landau

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3 Comments

Charles Landau Over a year ago

like this with ```, called the "backtick" it is shift+tilde on most western boards

Mac Over a year ago

This is how I was able to return what was being asked, took me a little while to debug but should work: GL = dict() for item in GR[1:]: GL[item[0]] = [int(item[1]),int(item[2]),int(item[3])] print(GL)

Charles Landau Over a year ago

@Mac if you answered your own question (or if you found an answer among the ones here) you should mark it as answered. (You can post an answer to your own question and mark it as the answer, that's allowed)

aydow · Accepted Answer · 2019-01-21 21:53:01Z

1

An alternative solution with Python 3 using map to convert the grades from strs to ints and partial unpacking to split each list into a person and their grades

In [111]: {person: list(map(int, grades)) for person, *grades in GR[1:]}
Out[111]:
{'PersonA': [100, 90, 80],
 'PersonB': [88, 99, 111],
 'PersonC': [45, 56, 67],
 'PersonD': [59, 61, 67],
 'PersonE': [73, 79, 83],
 'PersonF': [89, 97, 101]}

Python 2 equivalent

{g[0]: map(int, g[1:]) for g in GR[1:]}

edited Jan 21, 2019 at 21:53

answered Jan 21, 2019 at 21:47

aydow

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Comments

Mykola Zotko · Accepted Answer · 2019-01-21 22:07:26Z

0

Option 1:

GR_ = {i[0]: list(map(int, i[1:])) for i in GR[1:]}

Option 2:

GR_ = dict(map(lambda x: (x[0], list(map(int, x[1:]))), GR[1:]))

Output:

{'PersonA': [100, 90, 80],
 'PersonB': [88, 99, 111],
 'PersonC': [45, 56, 67],
 'PersonD': [59, 61, 67],
 'PersonE': [73, 79, 83],
 'PersonF': [89, 97, 101]}

edited Jan 21, 2019 at 22:07

answered Jan 21, 2019 at 21:53

Mykola Zotko

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Comments

hpaulj · Accepted Answer · 2019-01-21 22:38:58Z

Your GR is a numpy array (and the use of a[2,0] indexing confirms that):

In [179]: GR
Out[179]: 
array([['Student', 'Exam 1', 'Exam 2', 'Exam 3'],
       ['PersonA', '100', '90', '80'],
       ['PersonB', '88', '99', '111'],
       ['PersonC', '45', '56', '67'],
       ['PersonD', '59', '61', '67'],
       ['PersonE', '73', '79', '83'],
       ['PersonF', '89', '97', '101']], dtype='<U7')

So what you are doing is:

In [185]: {row[0]: row[1:] for row in GR[1:]}
Out[185]: 
{'PersonA': array(['100', '90', '80'], dtype='<U7'),
 'PersonB': array(['88', '99', '111'], dtype='<U7'),
 'PersonC': array(['45', '56', '67'], dtype='<U7'),
 'PersonD': array(['59', '61', '67'], dtype='<U7'),
 'PersonE': array(['73', '79', '83'], dtype='<U7'),
 'PersonF': array(['89', '97', '101'], dtype='<U7')}

The arrays of strings can easily be converted to integers with:

In [186]: {row[0]: row[1:].astype(int) for row in GR[1:]}
Out[186]: 
{'PersonA': array([100,  90,  80]),
 'PersonB': array([ 88,  99, 111]),
 'PersonC': array([45, 56, 67]),
 'PersonD': array([59, 61, 67]),
 'PersonE': array([73, 79, 83]),
 'PersonF': array([ 89,  97, 101])}

and on to lists:

In [187]: {row[0]: row[1:].astype(int).tolist() for row in GR[1:]}
Out[187]: 
{'PersonA': [100, 90, 80],
 'PersonB': [88, 99, 111],
 'PersonC': [45, 56, 67],
 'PersonD': [59, 61, 67],
 'PersonE': [73, 79, 83],
 'PersonF': [89, 97, 101]}

My nomination for the list conversion is:

In [188]: {name: [int(i) for i in grades] for name, *grades in GR[1:]}
Out[188]: 
{'PersonA': [100, 90, 80],
 'PersonB': [88, 99, 111],
 'PersonC': [45, 56, 67],
 'PersonD': [59, 61, 67],
 'PersonE': [73, 79, 83],
 'PersonF': [89, 97, 101]}

Mac · Accepted Answer · 2019-02-01 00:09:03Z

0

My apologies @Charles Landau, my python skill has improved drastically since asking this question.

GL = dict() 
     for i in GR[1:]:
          GL[i[0]] = [int(i[1]),int(i[2]),int(i[3])]
     print(GL)

answered Feb 1, 2019 at 0:09

Mac

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