Python – Extract Indices of substring matches

Given a String List, and a substring, extract list of indices of Strings, in which that substring occurs.

Input : test_list = [“Gfg is good”, “for Geeks”, “I love Gfg”, “Gfg is useful”], K = “Gfg”
Output : [0, 2, 3]
Explanation : “Gfg” is present in 0th, 2nd and 3rd element as substring.

Input : test_list = [“Gfg is good”, “for Geeks”, “I love Gfg”, “Gfg is useful”], K = “good”
Output : [0]
Explanation : “good” is present in 0th substring.

Method #2 : Using loop + enumerate()

This is brute way in which this task can be done. In this, we iterate for all the elements along with their indices using enumerate() and conditional statements are used to get required result.

Python3

# Python3 code to demonstrate working of
# Extract Indices of substring matches
# Using loop + enumerate()

# initializing list
test_list = ["Gfg is good", "for Geeks", "I love Gfg", "Its useful"]

# initializing K
K = "Gfg"

# printing original list
print("The original list : " + str(test_list))

# using loop to iterate through list
res = []
for idx, ele in enumerate(test_list):
  if K in ele:
    res.append(idx)

# printing result
print("The indices list : " + str(res))

Output

The original list : ['Gfg is good', 'for Geeks', 'I love Gfg', 'Its useful']
The indices list : [0, 2]

Method #2 : Using list comprehension + enumerate() 

This is yet another way in which this task can be solved. In this, we perform the similar task as above method using list comprehension and enumerate() is used to get compact solution.

Python3

# Python3 code to demonstrate working of
# Extract Indices of substring matches
# Using list comprehension + enumerate()

# initializing list
test_list = ["Gfg is good", "for Geeks", "I love Gfg", "Its useful"]

# initializing K
K = "Gfg"

# printing original list
print("The original list : " + str(test_list))

# using list comprehension and enumerate to offer compact solution
res = [idx for idx, val in enumerate(test_list) if K in val]

# printing result
print("The indices list : " + str(res))

Output

The original list : ['Gfg is good', 'for Geeks', 'I love Gfg', 'Its useful']
The indices list : [0, 2]