从列表中删除多个元素的更简洁的方法？

Question

I am trying to slice and strip a string. I have written the following code:

my_list = ['from ab1c_table in WXY\nprevious in time',
        'from abc3_table in MNO\nprevious in time',
        'from ab1_cow_table in DZMC1_IN tab\ncurrent in time',
        'from abc4_table in ERDU\ncurrent in time']
my_list_1 = []
for j in my_list:
  s = j.split(" ")
  s.remove('from')
  s.remove('in')
  s.remove('in')
  s.remove('time')

  for k in s:
    k = k.replace('current', '')
    k = k.replace('previous', '')
    k = k.replace('\n', '')
  my_list_1.append(k)
  if 'tab' in my_list_1:
    my_list_1.remove('tab')

print(my_list_1)

It is working fine but the issue is I have to remove each word separately. Is there a way to do it in fewer lines? The output I am looking for is:

['WXY', 'MNO']

EDIT 1 -

How do I get this output -

['ab1c_table', 'WXY', 'abc3_table', 'MNO', 'ab1_cow_table', 'DZMC1_IN', 'abc4_table', 'ERDU']

Answer 1

I am not sure if this is what you have in mind, but usually regular expressions are useful for extracting patterns from strings. For example:

import re
my_list = ['from ab1c_table in WXY\nprevious in time', 
           'from abc3_table in MNO\nprevious in time']

my_list1 = [re.findall(r" ([A-Z]{3})\n", s, )[0] for s in my_list]
print(my_list_1)

Edit:

Here is a modification of the regex pattern reflecting the additonal string samples provided by OP in a comment below:

mylist = ['from ab1c_table in WXY\nprevious in time', 
          'from abc3_table in MNO\nprevious in time', 
          'from ab1_cow_table in DZMC1_IN tab\ncurrent in time', 
          'from abc4_table in ERDU\ncurrent in time']

my_list1 = [re.findall(r"_table in (\S+)(?:| tab)\n.* in time", s)[0] for s in mylist]

print(my_list1)

This gives:

['WXY', 'MNO', 'DZMC1_IN', 'ERDU']

Edit 2:

Version capturing _table patterns:

import re
from itertools import chain

mylist = ['from ab1c_table in WXY\nprevious in time', 
          'from abc3_table in MNO\nprevious in time', 
          'from ab1_cow_table in DZMC1_IN tab\ncurrent in time', 
          'from abc4_table in ERDU\ncurrent in time']

my_list1 = list(chain(*[re.findall(r"from (\S+_table) in (\S+).*?\n.* in time", s)[0] for s in mylist]))

print(my_list1)

It gives:

['ab1c_table', 'WXY', 'abc3_table', 'MNO', 'ab1_cow_table', 'DZMC1_IN', 'abc4_table', 'ERDU']

Answer 2

Its not clear from the question what is variable in the strings, but it seems like this regular expression would do. The goal is to match everything that is static with some wildcards and parenthesized capture groups for the data you want in the result. Since you want two pieces of data in the order they are found in the string, you can create two capture groups and extend the result list.

import re
  
my_list = ['from ab1c_table in WXY\nprevious in time',
        'from abc3_table in MNO\nprevious in time',
        'from ab1_cow_table in DZMC1_IN tab\ncurrent in time',
        'from abc4_table in ERDU\ncurrent in time']

result = []
for value in my_list:
    result.extend(re.match(r"from (.+_table) in (\S+)", value).groups())
print(result)

Result

['ab1c_table', 'WXY', 'abc3_table', 'MNO', 'ab1_cow_table', 'DZMC1_IN', 'abc4_table', 'ERDU']

Answer 3

As I previously suggested, I think it can be done much easier with a simple split() . The strings always follow the same pattern. All you need to do is split at whitespace and take out the second and fourth element from the resulting lists.

elems = list()
for e in my_list:
    # e.g., the first element becomes
    # ['from', 'ab1c_table', 'in', 'WXY', 'previous', 'in', 'time']
    parts = e.split()
    elems.extend([parts[1], parts[3]])

print(elems)

Result:

['ab1c_table',
 'WXY',
 'abc3_table',
 'MNO',
 'ab1_cow_table',
 'DZMC1_IN',
 'abc4_table',
 'ERDU']

Answer 4

You can write a pattern that matches the strings and match for example either previous or current using (?:previous|current) , and capture the last part of the first line in group 1.

First check if there is a match, and if there is set the new value to the group 1 value.

If there is no match, leave the value unmodified.

\bfrom \w+ in (\w+)\nprevious in time\b

See the capture group value in green in this regex demo .

import re

pattern = r"\bfrom \w+ in (\w+)\n(?:previous|current) in time\b"
my_list = ['from ab1c_table in WXY\nprevious in time', 'from abc3_table in MNO\nprevious in time']

for n, i in enumerate(my_list):
    m = re.match(pattern, i)
    if m:
        my_list[n] = m.group(1)

print(my_list)

Output

['WXY', 'MNO']