how to filter a value from list in python?

Question

I have list of values , need to filter out values , that doesn't follow a naming convention.

like below list : list = ['a1-23','b1-24','c1-25','c1-x-25']
need to filter : all values that starts with 'c1-' , except 'c1-x-' )

output expected: ['a1-23','b1-24','c1-x-25']

list = ['a1-23','b1-24','c1-25','c1-x-25']
[x for x in list if not x.startswith('c1-')]
['a1-23', 'b1-24']

Please try to avoid using list as a variable name

Akshay Sehgal
– Akshay Sehgal

2020-11-29 22:53:30 +00:00
Commented Nov 29, 2020 at 22:53 — Akshay Sehgal
– Akshay Sehgal, Commented Nov 29, 2020 at 22:53

Mureinik · Accepted Answer · 2020-11-29 22:50:34Z

1

You have the right idea, but you're missing the handing of values that start with c1-x-:

[x for x in list if not x.startswith('c1-') or x.startswith('c1-x-')]

answered Nov 29, 2020 at 22:50

Mureinik

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1 Comment

Akshay Sehgal Over a year ago

Just adding my solution here in comments because its similar - [i for i in l if 'c1' not in i.split('-') or 'x' in i.split('-')]

ombk · Accepted Answer · 2020-11-30 08:26:03Z

1

import re

list1 = ['a1-23','b1-24','c1-25','c1-x-25',"c1-22"]
r = re.compile(r"\bc1-\b\d{2}$") # this regex matches anything with `c1-{2 digits}` exactly
[x for x in list1 if x not in list(filter(r.match,list1))]

# output
['a1-23', 'b1-24', 'c1-x-25']

So what my pattern does is match EXACTLY a word that starts with c1- and ends with two digits only.

Therefore, list(filter(r.match,list1)) will give us all the c1-## and then we do a list comprehension to filter out from list1 all the x's that aren't in the new provided list containing the matches.

x for x in [1,2,3] if x not in [1,2]
#output
[3]

edited Nov 30, 2020 at 8:26

answered Nov 29, 2020 at 23:13

ombk

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2 Comments

wscourge Over a year ago

Thank you for this code snippet, which might provide some limited, immediate help. A proper explanation would greatly improve its long-term value by showing why this is a good solution to the problem and would make it more useful to future readers with other, similar questions. Please edit your answer to add some explanation, including the assumptions you've made.

ombk Over a year ago

@wscourge will do

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