使用 python 删除列表中的空索引

Question

I'm working with strings which have horizontal tabs in them and are trying to convert them to lists. I figured out how to convert the tabs into commas, but the two tabs at the beginning and end of the string are also being converted into indexes by re.sub . This is creating an issue when using list comprehension to format the string as a list as '' is not an int . Is there a way forward from here? I'm not really keen on manually formatting each num_string prior to feeding it to python.

>>> import re
>>> num_string = "    29    10    16    "
>>> print((re.sub("[\\s]{1,}", ",", x)).split(','))
['', '29', '10', '16', '']
>>> num_list = [int(i) for i in num_string]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 1, in <listcomp>
ValueError: invalid literal for int() with base 10: ' '

Answer 1

I'd just use the built in split with no params. python 3.8.2 seems to work out of the box.

num_string = "    29    10    16    "
num_string.split()
['29', '10', '16']

But, to directly answer your question, you could also check the 'truthiness' of the value while coercing into ints.

import re

num_string = "    29    10    16    "
num_list = re.sub("[\\s]{1,}", ",", num_string).split(',')
num_list = [int(i) for i in num_list if i]
[29, 10, 16]

Answer 2

There is probably a better way to do this, but you can manually loop through (re.sub("[\\s]{1,}", ",", x)).split(',')

Here's how I imagine it:

subList=(re.sub("[\\s]{1,}", ",", x)).split(',')
for item in subList:
   if not item=='':
      item=int(item)
   else:
      continue

Answer 3

You can add a condition to your list comprehension to completely exclude the items from your resultant list:

>>> num_list = [int(i) for i in num_string if i != '']

or if you'd like to replace them with a default value instead

>>> num_list = [int(i) if i != '' else -1 for i in num_string]