Python program to extract only the numbers from a list which have some specific digits

Last Updated : 06 Apr, 2023

Given the elements List, extract numbers with specific digits.

Input : test_list = [3456, 23, 128, 235, 982], dig_list = [2, 3, 5, 4]
Output : [23, 235]
Explanation : 2, 3 and 2, 3, 5 are in digit list, hence extracted elements.
Input : test_list = [3456, 23, 28, 235, 982], dig_list = [2, 3, 5, 4, 8]
Output : [23, 28, 235]
Explanation : 2, 3; 2, 8 and 2, 3, 5 are in digit list, hence extracted elements.

Method #1 : Using list comprehension + all()

In this, we check for each element in number against the elements from target list to be present, if all are found in list, element is returned.

Python3

# Python3 code to demonstrate working of
# Elements with specific digits
# Using list comprehension + all()

# initializing list
test_list = [345, 23, 128, 235, 982]

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

# initializing digit list
dig_list = [2, 3, 5, 4]

# checking for all digits using all()
res = [sub for sub in test_list if all(
    int(ele) in dig_list for ele in str(sub))]

# printing result
print("Extracted elements : " + str(res))

Output

The original list is : [345, 23, 128, 235, 982]
Extracted elements : [345, 23, 235]

Time Complexity: O(n)
Auxiliary Space: O(1)

Method #2 : Using filter() + lambda + all()

In this, filtering of elements is done using filter() + lambda, all() is used to check for all the digits from other list.

Python3

# Python3 code to demonstrate working of
# Elements with specific digits
# Using filter() + lambda + all()

# initializing list
test_list = [345, 23, 128, 235, 982]

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

# initializing digit list
dig_list = [2, 3, 5, 4]

# filter() used to filter from logic
res = list(filter(lambda sub: all(
    int(ele) in dig_list for ele in str(sub)), test_list))

# printing result
print("Extracted elements : " + str(res))

Output

The original list is : [345, 23, 128, 235, 982]
Extracted elements : [345, 23, 235]

Time Complexity: O(n), where n is the length of the input list. This is because we’re using the built-in filter() + lambda + all() function which has a time complexity of O(n) in the worst case.
Auxiliary Space: O(n), as we’re using additional space res other than the input list itself with the same size of the input list.

Method #3 : Using Counter() + keys()+ all()

Python3

# Python3 code to demonstrate working of
# Elements with specific digits
from collections import Counter
# initializing list
test_list = [345, 23, 128, 235, 982]

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

# initializing digit list
dig_list = [2, 3, 5, 4]
freq = Counter(dig_list)
# checking for all digits using all() and keys() function
res = [sub for sub in test_list if all(
    int(ele) in freq.keys() for ele in str(sub))]

# printing result
print("Extracted elements : " + str(res))

Output

The original list is : [345, 23, 128, 235, 982]
Extracted elements : [345, 23, 235]

Time Complexity: O(n) as we used hashing for searching whether the digit is present in dig_list or not

Method #4: Using itertools.filterfalse() method

Python3

# Python3 code to demonstrate working of 
# Elements with specific digits
import itertools

# initializing list
test_list = [345, 23, 128, 235, 982]

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

# initializing digit list 
dig_list = [2, 3, 5, 4]

# filter() used to filter from logic 
res = list(itertools.filterfalse(lambda sub : not all(int(ele) in dig_list for ele in str(sub)), test_list))

# printing result 
print("Extracted elements : " + str(res))

Output

The original list is : [345, 23, 128, 235, 982]
Extracted elements : [345, 23, 235]

Time Complexity:O(N)
Auxiliary Space:O(N)

Method #5:Using recursion

Algorithm:

Define a function get_elements_with_specific_digits() that takes a list test_list and a digit list dig_list as input.
Check if the input list test_list is empty. If it is, return an empty list.
If the input list test_list is not empty, take the first element sub of the list.
Check if all of the digits in sub are in the digit list dig_list.
If all of the digits in sub are in dig_list, add sub to the result list and call the function recursively on the remaining elements of test_list (i.e., the elements starting from the second element).
If not all of the digits in sub are in dig_list, call the function recursively on the remaining elements of test_list (i.e., the elements starting from the second element).
Return the result list.

Python3

# Python3 code to demonstrate working of 
# Elements with specific digits
# Using recursion
def get_elements_with_specific_digits(test_list, dig_list):
    if not test_list:
        return []
    sub = test_list[0]
    if all(int(ele) in dig_list for ele in str(sub)):
        return [sub] + get_elements_with_specific_digits(test_list[1:], dig_list)
    else:
        return get_elements_with_specific_digits(test_list[1:], dig_list)
# initializing list
test_list = [345, 23, 128, 235, 982]
# printing original list
print("The original list is : " + str(test_list))
# initializing digit list 
dig_list = [2, 3, 5, 4]
# call the function to get the filtered list
res = get_elements_with_specific_digits(test_list, dig_list)
# printing result 
print("Extracted elements : " + str(res))

#This code is contributed by Jyothi Pinjala.

Output

The original list is : [345, 23, 128, 235, 982]
Extracted elements : [345, 23, 235]

Time complexity: O(n * m), where n is the length of the input list and m is the maximum length of an integer in the list (i.e., the number of digits in the largest integer). This is because we iterate through the entire list and for each integer in the list, we check if each of its digits is in the digit list.
Auxiliary space: O(n), where n is the length of the input list. This is because we create a new list to store the filtered elements.

Method 6: Use a for a loop

Approach:

Convert the digit list into a set for O(1) lookup time.
Initialize an empty list to store the filtered elements.
Iterate through each element of the test_list using a for loop.
Convert the current element to a string and convert each character to an integer using map() function.
Check if the set of digits in the digit list is a subset of the set of digits in the current element.
If it is, append the current element to the result list.
Return the result list.
Here is the code for the above approach with time and auxiliary space complexity:

Python3

def get_elements_with_specific_digits(test_list, dig_list):
    # Convert digit list to set
    dig_set = set(dig_list)
    # Initialize empty list for filtered elements
    res = []
    # Iterate through each element in test_list
    for ele in test_list:
        # Convert element to string and map each character to int
        digits = set(map(int, str(ele)))
        # Check if digit set is subset of dig_set
        if digits.issubset(dig_set):
            # Append current element to result list
            res.append(ele)
    # Return filtered list
    return res


# initializing list
test_list = [345, 23, 128, 235, 982]
# printing original list
print("The original list is : " + str(test_list))
# initializing digit list
dig_list = [2, 3, 5, 4]
# call the function to get the filtered list
res = get_elements_with_specific_digits(test_list, dig_list)
# printing result
print("Extracted elements : " + str(res))

Output

The original list is : [345, 23, 128, 235, 982]
Extracted elements : [345, 23, 235]

Time complexity: O(n * k), where n is the length of the test_list and k is the maximum number of digits in any element of the test_list.
Auxiliary space: O(n), where n is the length of the test_list.