CODEWITHSUNDEEP
python
Stacey
Stacey

Reputation: 5107

How add one to a list element?

I have an empty list called mylist which looks like

[None,None,None,None,None,None,None]

I have a for loop which will add one to each element each time its past over.

I am trying to add 1 to an element using:

mylist[i] = mylist[i]+1

but I get the error:

TypeError: unsupported operand type(s) for +: 'NoneType' and 'int'

The number of times the list is iterated over changes so ican't just add one to all elements.

The code I'm using is:

for j in range(0,bucketSize):
    for i in range (0,minibuckets):
        list[i] = list[i]+1

Upvotes: 0

Views: 93

Answers (4)

Hass786123
Hass786123

Reputation: 676

Use a simple list comprehension:

my_list = [None,None,None,None,None,None,None]

print(['1' if v is None else v for v in my_list])

Outputs:

['1', '1', '1', '1', '1', '1', '1']

Upvotes: 0

ruohola
ruohola

Reputation: 24107

You should initialise your list to be [0, 0, 0, 0, 0, 0, 0], because you cannot do None + 1. It really doesn't make sense to try to add 1 to something that is effectively nothing. None is a very different concept than 0.

For example:

mylist = [0] * 7
# or
mylist = [0 for i in range(7)]

 

Alternatively you can check for None in your inner for-loop:

if mylist[i] is None:
    mylist[i] = 1
else:
    mylist[i] += 1

Or the same check in one line:

mylist[i] = mylist[i] + 1 is mylist[i] is not None else 1

Upvotes: 6

Mehrdad Pedramfar
Mehrdad Pedramfar

Reputation: 11083

You can do something like this if you can not change None to 0:

mylist[i] = mylist[i]+1 if mylist[i] else 1

Upvotes: 0

ARF
ARF

Reputation: 31

None is very different from 0. In effect it is no value at all.

The simple solution to this is simply check for None in your loop.

for j in range(0,bucketSize):
    for i in range (0,minibuckets):
        if list[i] is None:
            list[i] = 1
        else:
            list[i] = list[i]+1

Alternatively initialize your list to 0 or replace None with 0 before starting.

Upvotes: 3

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