Adding spaces to items in list (Python)

问题:

I'm a Python noob and I need some help for a simple problem.

What I need to do is create a list with 3 items and add spaces before and after every item.

For example: l1 = ['a', 'bb', 'c']
should be transformed into: [' a ',' bb ',' c ']

I was trying to write something like this:

lst = ['a', 'bb', 'c']
for a in lst:
    print '  a  '

...and so on for the other elements, but I get a syntax error. Can anyone suggest me a working way to do this? Thanks.

回答1:

As always, use a list comprehension:

lst = [' {0} '.format(elem) for elem in lst]

This applies a string formatting operation to each element, adding the spaces. If you use python 2.7 or later, you can even omit the 0 in the replacement field (the curly braces).

回答2:

[ ' {} '.format(x) for x in lst ]

EDIT for python 3.6+:

you can use f-strings instead, see docs: https://www.python.org/dev/peps/pep-0498/

the example above would look like:

[ f' {x} ' for x in lst ]

回答3:

lst = ['a', 'bb', 'c']  
lst = [' ' + x + ' ' for x in lst]

回答4:

In [44]: l1 = ['a', 'bb', 'c']

In [45]: [' %s '%x for x in l1]
Out[45]: [' a ', ' bb ', ' c ']

回答5:

Indent your python code first! And then:

lst = ['a', 'b', 'c']
lst2 = [' ' + a + ' ' for a in lst]
print lst2

回答6:

Try this:

lst = [' ' + x + ' ' for x in ['a', 'bb', 'c']]

回答7:

>>> lst = ['a', 'bb', 'c']
>>> 
>>> [' {} '.format(x) for x in lst]
[' a ', ' bb ', ' c ']
>>>