使用Python将变量添加到列表中

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?

Answer 1

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.

Answer 2

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)

Answer 3

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

Answer 4

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