Add a variable into a list with Python

Question

I want add a variable to some of the items in mylist = ['A', 'B', 'C', 'D', 'E']. I tried something like this example...

for direction in ['Up', 'Down']:
    mylist = ['A{}', 'B', 'C{}', 'D', 'E'].format(direction)
    for x in mylist:
        print x

I want the output to be the following...

AUp
B
CUp
D
E
ADown
B
CDown
D
E

However, this isn't working. Is there a best way to add a variable in a list?

You need to describe the problem. "However, this isn't working." isn't very helpful. — Carcigenicate
– Carcigenicate, Commented Dec 15, 2017 at 18:56
print x.format(direction) in your 2nd for loop and remove the format from your list — depperm
– depperm, Commented Dec 15, 2017 at 18:57

cs95 · Accepted Answer · 2017-12-15 19:05:59Z

4

You cannot "vectorize" this formatting operation! It should be operated upon each string individually.

data = ['A{}', 'B', 'C{}', 'D', 'E']
direction = ['Up', 'Down']

for d in direction:
     print(*[x.format(d) for x in data], sep='\n')

AUp
B
CUp
D
E
ADown
B
CDown
D
E

Iterate over direction, and call format in a loop. If you're using python3, you can use the * iterable unpacking with a sep argument.

For python2, add a __future__ import statement at the top of your file, like this -

from __future__ import print_function

You can then use the print function to the same effect.

answered Dec 15, 2017 at 19:05

cs95

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Comments

Chun-Yen Wang · Accepted Answer · 2017-12-15 19:00:18Z

1

I would do this

mylist = ['A{}', 'B', 'C{}', 'D', 'E']
for direction in ['Up', 'Down']:
    for x in mylist:
        x = x.format(direction)
        print(x)

answered Dec 15, 2017 at 19:00

Chun-Yen Wang

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Comments

Ivan · Accepted Answer · 2017-12-15 19:13:42Z

1

With keeping the original mylist:

mylist = ['A', 'B', 'C', 'D', 'E']
for direction in ['Up', 'Down']:
    for x in mylist:
        print x + direction if x in ['A', 'C'] else x

answered Dec 15, 2017 at 19:13

Ivan

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Comments

Aaditya Ura · Accepted Answer · 2017-12-16 05:05:39Z

0

I have little different approach , You can do without loop without using two loop in just one line but result will be in list format :

 print(list(map(lambda x:list(map(lambda y:y.format(x),data)),direction)))

output:

[['AUp', 'B', 'CUp', 'D', 'E'], ['ADown', 'B', 'CDown', 'D', 'E']]

But if you want each element in new line then you have to iterate :

for k in direction:
    for i in data:
        print(i.format(k))

output:

AUp
B
CUp
D
E
ADown
B
CDown
D
E

answered Dec 16, 2017 at 5:05

Aaditya Ura

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