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.
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).
[ ' {} '.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 ]
ValueError: zero length field name in format
' {0} '. Pre 2.7, automatically numbering items wasn't possible.' {0} '.format(x) would work in all versions where .format() is supported, hence a better answer.lst = ['a', 'bb', 'c']
lst = [' ' + x + ' ' for x in lst]
In [44]: l1 = ['a', 'bb', 'c']
In [45]: [' %s '%x for x in l1]
Out[45]: [' a ', ' bb ', ' c ']
Indent your python code first! And then:
lst = ['a', 'b', 'c']
lst2 = [' ' + a + ' ' for a in lst]
print lst2
.format() method, or at a pinch the % string formatting operator, instead of concatenation. It is much more efficient.
Try this:
lst = [' ' + x + ' ' for x in ['a', 'bb', 'c']]
.format() method, or at a pinch the % string formatting operator, instead of concatenation. It is much more efficient.
['a', 'bb', 'c'] with any other list of strings, or with a variable containing a list (e.g., your lst)..format() is a more efficient approach in terms of performance.>>> lst = ['a', 'bb', 'c']
>>>
>>> [' {} '.format(x) for x in lst]
[' a ', ' bb ', ' c ']
>>>
