Python – Filter Tuples with Strings of specific characters

Last Updated : 24 Apr, 2023

Given a Tuple List, extract tuples, which have strings made up of certain characters.

Input : test_list = [(‘gfg’, ‘best’), (‘gfg’, ‘good’), (‘fest’, ‘gfg’)], char_str = ‘gfestb’
Output : [(‘gfg’, ‘best’), (‘fest’, ‘gfg’)]
Explanation : All tuples contain characters from char_str.

Input : test_list = [(‘gfg’, ‘best’), (‘gfg’, ‘good’), (‘fest’, ‘gfg’)], char_str = ‘gfstb’
Output : []
Explanation : No tuples with given characters.

Method #1 : Using all() + list comprehension

In this, we check for characters in strings, using in operator and all() is used to check if all elements in tuple have strings made up of certain characters.

Python3

   # Python3 code to demonstrate working of
# Filter Tuples with Strings of specific characters
# Using all() + list comprehension
 
# initializing lists
test_list = [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')]
 
# printing original lists
print("The original list is : " + str(test_list))
 
# initializing char_str
char_str = 'gfestb'
 
# nested all(), to check for all characters in list, 
# and for all strings in tuples
res = [sub for sub in test_list if all(
    all(el in char_str for el in ele) for ele in sub)]
 
# printing result
print("The filtered tuples : " + str(res))
 
  

Output

The original list is : [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')] The filtered tuples : [('gfg', 'best'), ('fest', 'gfg')]

Time Complexity: O(n²)
Auxiliary Space: O(n)

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

Similar to the above method, difference being filter() + lambda is used to perform task of filtering.

Python3

   # Python3 code to demonstrate working of
# Filter Tuples with Strings of specific characters
# Using filter() + lambda + all()
 
# initializing lists
test_list = [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')]
 
# printing original lists
print("The original list is : " + str(test_list))
 
# initializing char_str
char_str = 'gfestb'
 
# nested all(), to check for all characters in list, 
# and for all strings in tuples filter() is used 
# to extract tuples
res = list(filter(lambda sub: all(all(el in char_str for el in ele)
                                  for ele in sub), test_list))
 
# printing result
print("The filtered tuples : " + str(res))
 
  

Output

The original list is : [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')] The filtered tuples : [('gfg', 'best'), ('fest', 'gfg')]

Time Complexity: O(n²)
Auxiliary Space: O(n)

Method #3 : Using replace(),join() and len() methods

Python3

   # Python3 code to demonstrate working of
# Filter Tuples with Strings of specific characters
 
# initializing lists
test_list = [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')]
 
# printing original lists
print("The original list is : " + str(test_list))
 
# initializing char_str
char_str = 'gfestb'
res=[]
for i in test_list:
    x="".join(i)
    for j in char_str:
        x=x.replace(j,"")
    if(len(x)==0):
        res.append(i)
# printing result
print("The filtered tuples : " + str(res))
 
  

Output

The original list is : [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')] The filtered tuples : [('gfg', 'best'), ('fest', 'gfg')]

Time complexity: O(n*m), where n is the length of the input list and m is the length of the char_str.
Auxiliary space: O(k), where k is the number of tuples that satisfy the condition, as we are storing those tuples in a new list.

Method #4 : Using re

One approach to solve this problem is using a regular expression. The idea is to join the tuples into a single string and then use re.search to check if all characters are in the character string. Here is the code:

Python3

   import re
 
def filter_tuples(test_list, char_str):
    res = []
    for sub in test_list:
        x = "".join(sub)
        if re.search("^[" + char_str + "]+$", x):
            res.append(sub)
    return res
 
test_list = [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')]
char_str = 'gfestb'
print(filter_tuples(test_list, char_str))
 
  

Output

[('gfg', 'best'), ('fest', 'gfg')]

Time complexity: O(n^2)
Auxiliary Space: O(n)

Method #5: Using Set Operations

Initialize the input list and the characters string.
Convert the characters string into a set for faster lookups.
Iterate through each tuple in the input list.
Convert each tuple into a set of characters.
Use the set intersection operation to find the common characters between the tuple and the characters string.
Check if the length of the intersection set is equal to the length of the tuple. If it is, then all the characters in the tuple are present in the characters string.
If step 6 is true, append the tuple to the result list.
Return the result list.

Python3

   # Python3 code to demonstrate working of
# Filter Tuples with Strings of specific characters
 
# initializing lists
test_list = [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')]
 
# printing original lists
print("The original list is : " + str(test_list))
 
# initializing char_str
char_str = 'gfestb'
 
# converting char_str to a set
char_set = set(char_str)
 
# initializing result list
res = []
 
# iterating through each tuple in the input list
for tup in test_list:
    # converting tuple to a set of characters
    tup_set = set(''.join(tup))
    # checking if all characters in the tuple are in char_set
    if len(tup_set.intersection(char_set)) == len(tup_set):
        res.append(tup)
 
# printing result
print("The filtered tuples : " + str(res))
 
  

Output

The original list is : [('gfg', 'best'), ('gfg', 'good'), ('fest', 'gfg')] The filtered tuples : [('gfg', 'best'), ('fest', 'gfg')]

Time complexity: O(n*m), where n is the number of tuples and m is the length of the longest tuple. In the worst case, we need to iterate through every character in every tuple.
Auxiliary space: O(m), where m is the length of the longest tuple. We need to create a set for each tuple.