Find sub-string with expressions inside a list of string in Python

Question

Have an array as shown below.

arrayy = ['top,tree,branch,bla-top,tree,ascb-red/blue', 'tree,leaves,mmn-tree,leaves,mscb-gra/gre', 'leaves,bird,responder,mon-leaves,bird,ascb-yoo/yee','tree,leaves,mount-road,cycle-roo/soo']

Is there a simple way to find the index which contains a sub-string inside a list of string ?
For eg, I wanted to search for "leaves,bird*-leaves,bird*" and wanted to return the index for the same.

Tried the below code,

def find_index_sub_string(needle,haystack):
    return [i for i, x in enumerate(haystack) if needle in x]

Able to search for leave,bird but unable to search like "leaves,bird*-leaves,bird*"

Is there any better way to search and get the require string ?

UPDATE:

Got it working with below code.

search_re = re.compile("leaves,bird.*-leaves,bird.*")

for i in range (len(arrayy)):
    if re.match(search_re, arrayy[i]):
        print i

For leaves,bird*-leaves,bird* search you would need to use search_re = re.compile("leaves,bird.*-leaves,bird.*") out of your loop and then do if search_re.search() within your loop — urban
– urban, Commented Dec 22, 2019 at 10:16
Hello. but when if I do search_re.search , will that return all the index's ? or do I need to cycle through to get the index ? — Vimo
– Vimo, Commented Dec 22, 2019 at 10:43
You will still need to iterate similar way with @Patrick Artner 's solution — urban
– urban, Commented Dec 22, 2019 at 10:50
"leaves,bird*-leaves,bird*" is not present in any of the string present in arrayy right? I didn't properly understand the question you asked. Can someone explain it to me please. — Ch3steR
– Ch3steR, Commented Dec 22, 2019 at 10:56
@Ch3steR I am trying to search for that string using * expression i.e. not giving the full absolute string. — Vimo
– Vimo, Commented Dec 22, 2019 at 10:58

Patrick Artner · Accepted Answer · 2019-12-22 12:20:55Z

2

Most of the time you want to find (complex) patterns in texts, regular expressions can do it:

import re

data = ['top,tree,branch,bla-top,tree,ascb-red/blue', 
        'tree,leaves,mmn-tree,leaves,mscb-gra/gre', 
        'leaves,bird,responder,mon-leaves,bird,ascb-yoo/yee',
        'tree,leaves,mount-road,cycle-roo/soo']

patt1 = r"leaves,bird.*-leaves,bird" 
patt2 = r"tree" 

for patt in (patt1,patt2):
    print (f"'{patt}' in text:") # py 3, for 2 use: print '{} in text:'.format(patt)
    for idx,text in enumerate(data): 
        if re.search(patt,text):   # modified from re.match wich only looks at start of text
            print(idx, text)    # py 3, for 2 use: print idx,text

Output:

'leaves,bird.*-leaves,bird' in text:
2 leaves,bird,responder,mon-leaves,bird,ascb-yoo/yee
'tree' in text:
1 tree,leaves,mmn-tree,leaves,mscb-gra/gre
3 tree,leaves,mount-road,cycle-roo/soo

You can develop your matching patterns online, f.e. on http://www.regex101.com - and get it to explain them to you as well.

If you want to start with regex, this is a fun way to do so: https://regexcrossword.com/ (just a fan, not affiliated ;o) ) - the official site to look at would be https://docs.python.org/3/library/re.html

My second pattern does not need regex - a simple if 'tree' in text: would have had the same effect.

edited Dec 22, 2019 at 12:20

answered Dec 22, 2019 at 10:16

Patrick Artner

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2 Comments

urban Over a year ago

Isn't better to use re.search() instead of re.match(). Will be slower probably but will match cases where the entry does not start with "leaves", like: "mount-cycle,tree,leaves,mount-road,cycle-roo/soo"

Patrick Artner Over a year ago

@urban good point, if its inside the string, re.match won't get it. incorporating your advice.#

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