Replace None value in list?

Question

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

Asked By: user7172

||

Source

Answer 1

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.

Answered By: Martijn Pieters

Answer 2

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

Answered By: K DawG

Answer 3

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']

Answered By: Abhijit

Answer 4

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]

Answered By: Saullo G. P. Castro

Answer 5

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.

Answered By: Uzzy

Answer 6

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)

Answered By: Pavan Chandaka

Answer 7

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

Answered By: program4people

Replace None value in list?

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