Python | Filter String with substring at specific position

Sometimes, while working with Python string lists, we can have a problem in which we need to extract only those lists that have a specific substring at a specific position. This kind of problem can come in data processing and web development domains. Let us discuss certain ways in which this task can be performed. 

Method #1: Using list comprehension + list slicing The combination of the above functionalities can be used to perform this particular task. In this, we check for substring range using list slicing, and the task of extraction list is compiled in list comprehension. 

Python3

# Python3 code to demonstrate
# Filter String with substring at specific position
# using list comprehension + list slicing

# Initializing list
test_list = ['geeksforgeeks', 'is', 'best', 'for', 'geeks']

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

# Initializing substring
sub_str = 'geeks'

# Initializing range
i, j = 0, 5

# Filter String with substring at specific position
# using list comprehension + list slicing
res = [ele for ele in test_list if ele[i: j] == sub_str]

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

Output : 

The original list is : ['geeksforgeeks', 'is', 'best', 'for', 'geeks']
Filtered list : ['geeksforgeeks', 'geeks']

Method #2 : Using filter() + lambda The combination of above methods can be used to perform this task. In this, we filter the elements using logic compiled using lambda using filter(). 

Python3

# Python3 code to demonstrate
# Filter String with substring at specific position
# using filter() + lambda

# Initializing list
test_list = ['geeksforgeeks', 'is', 'best', 'for', 'geeks']

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

# Initializing substring
sub_str = 'geeks'

# Initializing range
i, j = 0, 5

# Filter String with substring at specific position
# using filter() + lambda
res = list(filter(lambda ele: ele[i: j] == sub_str, test_list))

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

Output : 

The original list is : ['geeksforgeeks', 'is', 'best', 'for', 'geeks']
Filtered list : ['geeksforgeeks', 'geeks']

Method #3: Using find() method

Python3

# Python3 code to demonstrate
# Filter String with substring at specific position

# Initializing list
test_list = ['geeksforgeeks', 'is', 'best', 'for', 'geeks']

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

# Initializing substring
sub_str = 'geeks'

# Initializing range
i, j = 0, 5

# Filter String with substring at specific position
res=[]
for k in test_list:
    if(k.find(sub_str)==i):
        res.append(k)


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

Output

The original list is : ['geeksforgeeks', 'is', 'best', 'for', 'geeks']
Filtered list : ['geeksforgeeks', 'geeks']