I have a question regarding inverse filtering in dictionary. I have a dictionary as:

dico = {
   Pierre:{
         'Math':16,
         'Chimie':09,
         'Dessin':18,
         'Electronic':20,
         'Info':14,
         }
    Jean:{
         'Physics':10,
         'Chimie':20,
         'Dessin':13,
         'Electronic':16,
         'Info':17,
         }
    Giovani:{
         'Math':16,
         'Physics':14,
         'Chimie':13,
         'Dessin':14,
         'Electronic':17,
         'Info':12,
         }

    ...
    }

What I want is to extract all the student which attempt each exam, and have output as set or list such as:

'Math': [pierre,Giovanie], 'Physics': [Jean, Giovanie]

exam_set = [{k:v for (k, v) in i.items()}
                for i in dico if i.get(v) != 0]

But is doesn't work and I don't know how to how to fix that.

CodePudding user response：

Try:

dct = {
    "Pierre": {
        "Math": 16,
        "Chimie": 9,
        "Dessin": 18,
        "Electronic": 20,
        "Info": 14,
    },
    "Jean": {
        "Physics": 10,
        "Chimie": 20,
        "Dessin": 13,
        "Electronic": 16,
        "Info": 17,
    },
    "Giovani": {
        "Math": 16,
        "Physics": 14,
        "Chimie": 13,
        "Dessin": 14,
        "Electronic": 17,
        "Info": 12,
    },
}

out = {}
for k, v in dct.items():
    for i in v:
        out.setdefault(i, []).append(k)

print(out)

Prints:

{
    "Math": ["Pierre", "Giovani"],
    "Chimie": ["Pierre", "Jean", "Giovani"],
    "Dessin": ["Pierre", "Jean", "Giovani"],
    "Electronic": ["Pierre", "Jean", "Giovani"],
    "Info": ["Pierre", "Jean", "Giovani"],
    "Physics": ["Jean", "Giovani"],
}

Or if you want sets:

out = {}
for k, v in dct.items():
    for i in v:
        out.setdefault(i, set()).add(k)

Prints:

{
    "Math": {"Giovani", "Pierre"},
    "Chimie": {"Jean", "Giovani", "Pierre"},
    "Dessin": {"Jean", "Giovani", "Pierre"},
    "Electronic": {"Jean", "Giovani", "Pierre"},
    "Info": {"Jean", "Giovani", "Pierre"},
    "Physics": {"Jean", "Giovani"},
}

CodePudding user response：

i commented everything play with the code so you can get better at python

students = { # students
"Pierre":{
         'Math':16,
         'Chimie':90,
         'Dessin':18,
         'Electronic':20,
         'Info':14,
         },
"Jean":{
         'Physics':10,
         'Chimie':20,
         'Dessin':13,
         'Electronic':16,
         'Info':17,
         },
"Giovani":{
         'Math':16,
         'Physics':14,
         'Chimie':13,
         'Dessin':14,
         'Electronic':17,
         'Info':12,
         }
         
}
data = {} # create data dict

for student in students: # loop to every student
    for exam in students[student]: # loop in the student exams
        if exam in data: # check if exam list exist
            data[exam].append(student) # append to the exam list
        else: # else create an exam list
            data[exam] = [student] # create and add the student to the exam list

print(data) # let see the result

CodePudding user response：

defaultdict can handle this very easily

from collections import defaultdict

def solution(dic):
    res = defaultdict(list)
    for k, v in students.items():
        for k2, v2 in v.items():
            res[k2].append(k)
    return dict(res)

print(solution(dico))

OUTPUT:

{'Math': ['Pierre', 'Giovani'], 'Chimie': ['Pierre', 'Jean', 'Giovani'], 'Dessin': ['Pierre', 'Jean', 'Giovani'], 'Electronic': ['Pierre', 'Jean', 'Giovani'], 'Info': ['Pierre', 'Jean', 'Giovani'], 'Physics': ['Jean', 'Giovani']}