CODEWITHSUNDEEP
pythonlistreplace
user7172
user7172

Reputation: 974

Replace None value in list?

I have:

d = [1,'q','3', None, 'temp']

I want to replace None value to 'None' or any string

expected effect:

d = [1,'q','3', 'None', 'temp']

a try replace in string and for loop but I get error:

TypeError: expected a character buffer object

Upvotes: 54

Views: 122107

Answers (7)

program4people
program4people

Reputation: 1

My solution was to match for None and replace it.

def fixlist(l: list):
    for i, v in enumerate(l):
        if v is None:
            l[i] = 0

Upvotes: 0

Pavan Chandaka
Pavan Chandaka

Reputation: 12751

I did not notice any answer using lambda..

Someone who wants to use lambda....(Look into comments for explanation.)

#INPUT DATA
d =[1,'q','3', None, 'temp']

#LAMBDA TO BE APPLIED
convertItem = lambda i : i or 'None' 

#APPLY LAMBDA
res = [convertItem(i) for i in d]

#PRINT OUT TO TEST
print(res)

Upvotes: 1

Saullo G. P. Castro
Saullo G. P. Castro

Reputation: 58895

You can simply use map and convert all items to strings using the str function:

map(str, d)
#['1', 'q', '3', 'None', 'temp']

If you only want to convert the None values, you can do:

[str(di) if di is None else di for di in d]

Upvotes: 17

Uzzy
Uzzy

Reputation: 489

Starting Python 3.6 you can do it in shorter form:

d = [f'{e}' for e in d]

hope this helps to someone since, I was having this issue just a while ago.

Upvotes: 4

Deelaka
Deelaka

Reputation: 13693

Using a lengthy and inefficient however beginner friendly for loop it would look like:

d = [1,'q','3', None, 'temp']
e = []

for i in d:
    if i is None: #if i == None is also valid but slower and not recommended by PEP8
        e.append("None")
    else:
        e.append(i)

d = e
print d
#[1, 'q', '3', 'None', 'temp']

Only for beginners, @Martins answer is more suitable in means of power and efficiency

Upvotes: 3

Abhijit
Abhijit

Reputation: 63737

List comprehension is the right way to go, but in case, for reasons best known to you, you would rather replace it in-place rather than creating a new list (arguing the fact that python list is mutable), an alternate approach is as follows

d = [1,'q','3', None, 'temp', None]
try:
    while True:
        d[d.index(None)] = 'None'
except ValueError:
    pass

>>> d
[1, 'q', '3', 'None', 'temp', 'None']

Upvotes: 2

Martijn Pieters
Martijn Pieters

Reputation: 1121894

Use a simple list comprehension:

['None' if v is None else v for v in d]

Demo:

>>> d = [1,'q','3', None, 'temp']
>>> ['None' if v is None else v for v in d]
[1, 'q', '3', 'None', 'temp']

Note the is None test to match the None singleton.

Upvotes: 94

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