Can't convert list of lists to dictionary in python-CodePudding

I have a list of lists:-

[['Grade', 'V A'], ['Attendance', '16/26'], ['Session timings', '8:00 am - 8:40 am'], ['Grade', 'VII A'], ['Attendance', '24/31'], ['Session timings', '8:50 am - 9:30 am'], ['Grade', 'IX A'], ['Attendance', '20/26'], ['Session timings', '9:40 am - 10:20 am'], ['Grade', 'IX B'], ['Attendance', '21/25'], ['Session timings', '10:50 am - 11:30 am']]

And want to convert it to dictionary like this:-

{{"Grade":"V A"}, {"Attendance": "16/26"} ... }

I tried using the zip method:-

keys = []
values = []

for i in range(0, 12):
    string = str(message_list[i]).replace(',',';').replace('[','').replace(']','').replace("'","").split(";")
    keys.append(string[0])
    values.append(string[1])

new_dict = dict(zip(keys, values))
print(new_dict)

But it only prints:-

{'Grade': ' IX B', 'Attendance': ' 21/25', 'Session timings': ' 10:50 am - 11:30 am'}

It prints only of Grade IX B, not other 3 grades. Please help me with the code...

But when I use new_dict = list(zip(keys, values)) it prints the whole as a list of tuples:

[('Grade', ' V A'), ('Attendance', ' 16/26'), ('Session timings', ' 8:00 am - 8:40 am'), ('Grade', ' VII A'), ('Attendance', ' 24/31'), ('Session timings', ' 8:50 am - 9:30 am'), ('Grade', ' IX A'), ('Attendance', ' 20/26'), ('Session timings', ' 9:40 am - 10:20 am'), ('Grade', ' IX B'), ('Attendance', ' 21/25'), ('Session timings', ' 10:50 am - 11:30 am')]

Then why doesn't it print full dictionary? Please help me with the code.

Thank you!

CodePudding user response：

You can't have the same key (e.g., 'Grade') repeated more than once in a dictionary... Keys must be unique.

You could do something like this instead:

from collections import defaultdict

d = defaultdict(list)
for k, v in lst:
    d[k].append(v)
d = dict(d)

The result is:

{'Grade': ['V A', 'VII A', 'IX A', 'IX B'],
 'Attendance': ['16/26', '24/31', '20/26', '21/25'],
 'Session timings': ['8:00 am - 8:40 am', '8:50 am - 9:30 am', '9:40 am - 10:20 am', '10:50 am - 11:30 am']}

CodePudding user response：

The reason is you are overwriting the already existing key and hence can see only the last entry of the list in your dict. Another approach can be to have a nested dict as below:

{
    'Grade-V A': {
        'Attendance': '16/26',
        'Session timings': '8:00 am - 8:40 am'
    },
    'Grade-VII A': {
        'Attendance': '24/31',
        'Session timings': '8:50 am - 9:30 am'
    },
    'Grade-IX A': {
        'Attendance': '20/26',
        'Session timings': '9:40 am - 10:20 am'
    },
    'Grade-IX B': {
        'Attendance': '21/25',
        'Session timings': '10:50 am - 11:30 am'
    }
}

with the below code:

data = [['Grade', 'V A'], ['Attendance', '16/26'], ['Session timings', '8:00 am - 8:40 am'], ['Grade', 'VII A'], ['Attendance', '24/31'], ['Session timings', '8:50 am - 9:30 am'], ['Grade', 'IX A'], ['Attendance', '20/26'], ['Session timings', '9:40 am - 10:20 am'], ['Grade', 'IX B'], ['Attendance', '21/25'], ['Session timings', '10:50 am - 11:30 am']]

output = {}
for item in data:
    if item[0] == 'Grade':
        grade = item[0] '-' item[1]
        output[grade] = {}
    else:
        output[grade][item[0]] = item[1]
        
print (output)