Appending a list through if condition in python

Question

This could be a very basic question, but I realized I am not understanding something.

When appending new things in for loop, how can I raise conditions and still append the item?

For instance:

alist = [0,1,2,3,4,5]
new = []
for n in alist:
    if n == 5:
        continue
    else:
        new.append(n+1)

print(new)

Gets me

[1, 2, 3, 4, 5]

How do I get

[1, 2, 3, 4, 5, 5] # 4 is incremented, 5 is added 'as is'

Essentially, I want to tell python to not go through n+1 when n==5.

Would this be the only solution? append n==5 separately in a list and then sum new and the separate list?

new.append(n) rather than continue?

Loocid
– Loocid

2018-10-22 02:51:50 +00:00
Commented Oct 22, 2018 at 2:51 — Loocid
– Loocid, Commented Oct 22, 2018 at 2:51
new = [1, 2, 3, 4, 5, 5]?

Stephen Rauch
– Stephen Rauch ♦

2018-10-22 02:54:52 +00:00
Commented Oct 22, 2018 at 2:54 — Stephen Rauch
– Stephen Rauch ♦, Commented Oct 22, 2018 at 2:54
@StephenRauch I'd like to get the result using the for loop

Asteroid098
– Asteroid098

2018-10-22 02:56:00 +00:00
Commented Oct 22, 2018 at 2:56 — Asteroid098
– Asteroid098, Commented Oct 22, 2018 at 2:56

Cypherius · Accepted Answer · 2018-10-22 02:57:49Z

8

Why don't you just append the 5 instead of using continue, is there any other condition?

for n in alist:
    if n == 5:
        new.append(n)
    else:
        new.append(n+1)

answered Oct 22, 2018 at 2:57

Cypherius

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1 Comment

Asteroid098 Over a year ago

Right, use append because it appends sequentially! Make sense. Thank you!

Stephen Rauch · Accepted Answer · 2018-10-22 02:59:16Z

2

You can use the fact the a boolean True is 1 while a False is 0 combined with a list comprehension like:

Code:

[x + int(i != 5) for i, x in enumerate(alist)]

Test Code:

alist = [0, 1, 2, 3, 4, 5]
new = [x + int(i != 5) for i, x in enumerate(alist)]
print(new)

Result:

[1, 2, 3, 4, 5, 5]

answered Oct 22, 2018 at 2:59

Stephen Rauch♦

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Comments

Dennis Wang · Accepted Answer · 2018-10-22 08:47:04Z

1

Seems like you didn't get the point of 'continue'. The Python keyword 'continue', means you do nothing in that if condition, so basically you tell the program "do nothing" when n == 5 and if n is not 5, you do some operation. That's why you got your original result. Hope it may help.

answered Oct 22, 2018 at 8:47

Dennis Wang

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