List in dict is being overriden when I add a sec. list to dict

Question

I want to add username and dateTimeHold to bigData, if it already exists, then I only want to add dateTimeHold, else add username and dateTimeHold.

When I'm trying with this code, it's just overwriting:

dateTimeHold = ('09-07-2019', '09.00 - 16.00', 'Red')
username = 'James'
bigData = {
        'Peter': [('08-07-2019', '06.00 - 07.00', 'Blue')], 
        'James': [('08-07-2019', '06.00 - 07.00', 'Blue')]
        }

if username != bigData.keys():
    listTime = []
    listTime.append(dateTimeHold)
    bigData[username] = listTime
else:
    bigData[username][listTime].append(dateTimeHold)

Output:

{
    'Peter': [('08-07-2019', '06.00 - 07.00', 'Blue')], 
    'James': [('09-07-2019', '09.00 - 16.00', 'Red')]
}

What I want it to do:

{
    'Peter': [('08-07-2019', '06.00 - 07.00', 'Blue')], 
    'James': [('08-07-2019', '06.00 - 07.00', 'Blue'), ('09-07-2019', '09.00 - 16.00', 'Red')]
}

What is `listTime` in your `else`? (may want to start looking there). I.e. `bigData[username][listTime].append(dateTimeHold)` should be `bigData[username].append(dateTimeHold)` — Error - Syntactical Remorse, Jul 10 '19 at 15:32
it refers to the list there allready have been created up in the if. I dont know if its correct im new to python — Christian Græsborg, Jul 10 '19 at 15:41
You should look into scopes... as it sits you code is bug prone. — Error - Syntactical Remorse, Jul 10 '19 at 15:42
if i change != to == the the else statment works but i get an keyError at the first if statment — Christian Græsborg, Jul 10 '19 at 16:04
@ChristianGræsborg Exactly, read my first comment. You are trying to use a key on a list. — Error - Syntactical Remorse, Jul 10 '19 at 17:11

score 0 · Accepted Answer · answered Jul 10 '19 at 17:44

Proper sintax

if username not in bigData.keys():
    bigData[username] = [dateTimeHold]
else:
    bigData[username].append(dateTimeHold)

About your if condition

Using if username != bigData.keys(): will always be true because anything your variable username is will be different of dict_keys(['Peter', 'James']).

If you want to see if a value is inside a list you should use in or not in instead

'Peter' != bigData.keys() is True
'Peter' not in bigData.keys() is False

About your else

The sintax is not right, listTime doesn't exists in your else scope.

Besides that check out this content of adding new keys in dict to understand why bigData[username][listTime].append(dateTimeHold) generates an error and whybigData[username].append(dateTimeHold) works.

score 0 · Answer 2 · answered Jul 10 '19 at 17:52

Try the code and see the comments in line for the corrections

dateTimeHold = ('09-07-2019', '09.00 - 16.00', 'Red')
username = 'James'
bigData = {'Peter': [('08-07-2019', '06.00 - 07.00', 'Blue')], 
           'James': [('08-07-2019', '06.00 - 07.00', 'Blue')}
if username not in bigData.keys(): #1. Check for the username in the keys
    listTime = []
    listTime.append(dateTimeHold)
    bigData[username] = listTime
else:
    bigData[username].append(dateTimeHold) #2.right way to append

List in dict is being overriden when I add a sec. list to dict

2 Answers2