CODEWITHSUNDEEP
python
Matt
Matt

Reputation: 171

Compare two lists and replace values in list one with values in list 2

I have two lists. 

a = [1,2,3,4,0,4,5,6,3,6,0,5,6,8,0,3]
b = [1,2, None,4,5,4,5,6,3,6,7,5,6,8,4, None]

I want a resulting list like this. 

new_list = [1,2,3,4,5,4,5,6,3,6,7,5,6,8,4,3]

List b is only replacing the 0's in list a and not touching the other elements for example the None is not being replaced.

How can I get about doing this? Thanks in advance. Please do let me know if you need any other information.

I have tried the following and it does not work.

_ = dict(zip(a,b))
for k,v in _.items():
   if k == 0:
       a = a.replace(k,v)

Upvotes: 2

Views: 2098

Answers (4)

lifebalance
lifebalance

Reputation: 1927

out = []
for ea, eb in zip(a, b): 
  res = ea 
  # if element in a is 0 and corresponding element in b is not None
  if ea == 0 and eb:
    res = eb 
  out.append(res)

assert out == [1,2,3,4,5,4,5,6,3,6,7,5,6,8,4,3]

And for a = [0, 1, 0] and b = [None, 2, 3] this will generate 

out == [0, 1, 3]

Upvotes: 0

U13-Forward
U13-Forward

Reputation: 71580

Or enumerate + a loop + indexing:

l=[i for i,v in enumerate(a) if v==0]
for i in l:
    a[i]=b[i]

And now:

print(a)

Is:

[1, 2, 3, 4, 5, 4, 5, 6, 3, 6, 7, 5, 6, 8, 4, 3]

Upvotes: 0

user10693394
user10693394

Reputation:

try with this:

a = [1, 0, 3, 4, 0, 6, 7, 0, 9]
b = [1, 2, None, 4, 5, 6, None, 8, 9]

k = 0  # Counter
c = [0] * len(a)  # Creating the 'c' list
for n in a:  # Reading 'a' list
    if n != 0: 
        c[k] = a[k]  # Copying 'a' list objects, when 'n' != 0, in 'c' list
    else:
        c[k] = b[k]  # Copying 'b' list objects, when 'n' == 0, in 'c' list
    k = k + 1

Upvotes: 0

slider
slider

Reputation: 12990

You can use zip and a simple list comprehension to generate a new list by picking elements of a if they're not 0 or elements of b if the corresponding a element is zero:

a = [1, 2, 3, 4, 0, 4, 5, 6, 3, 6, 0, 5, 6, 8, 0, 3]
b = [1, 2, None, 4, 5, 4, 5, 6, 3, 6, 7, 5, 6, 8, 4, None]

result = [y if x == 0 else x for x, y in zip(a, b)]
print(result)
# [1, 2, 3, 4, 5, 4, 5, 6, 3, 6, 7, 5, 6, 8, 4, 3]

Upvotes: 3

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